Android P 图像显示系统（二）GraphicBuffer
2018-08-16 本文已影响460人
夕月风
GraphicBuffer和Gralloc分析
BufferQueue中的Buffer对象，我们用的都是GraphicBuffer，那么GraphicBuffer是怎么来的呢？接下里我们具体来看这里的流程。
Surface是Andorid窗口的描述，是ANativeWindow的实现；同样GraphicBuffer是Android中图形Buffer的描述，是ANativeWindowBuffer的实现。而一个窗口，可以有几个Buffer。
GraphicBuffer定义
* frameworks/native/include/ui/GraphicBuffer.h
class GraphicBuffer
: public ANativeObjectBase<ANativeWindowBuffer, GraphicBuffer, RefBase>,
public Flattenable<GraphicBuffer>
{
friend class Flattenable<GraphicBuffer>;
public:
其中ANativeObjectBase是一个模板类，定义如下：
* frameworks/native/include/ui/ANativeObjectBase.h
template <typename NATIVE_TYPE, typename TYPE, typename REF,
typename NATIVE_BASE = android_native_base_t>
class ANativeObjectBase : public NATIVE_TYPE, public REF
{
public:
// Disambiguate between the incStrong in REF and NATIVE_TYPE
void incStrong(const void* id) const {
REF::incStrong(id);
}
void decStrong(const void* id) const {
REF::decStrong(id);
}
这样ANativeObjectBase继承ANativeWindowBuffer和RefBase，GraphicBuffer继承ANativeObjectBase和Flattenable。
这样做的目的：
- RefBase使GraphicBuffer支持引用计数控制
- Flattenable使GraphicBuffer支持序列化。
其中的关键类 ANativeWindowBuffer，它是一个结构体，是对Native Buffer的一个描述，其定义如下：
* frameworks/native/libs/nativebase/include/nativebase/nativebase.h
typedef struct ANativeWindowBuffer
{
#ifdef __cplusplus
// 构造函数，decStrong和incStrong的实现；得初始化common
#endif
struct android_native_base_t common;
int width;
int height;
int stride;
int format;
int usage_deprecated;
uintptr_t layerCount;
void* reserved[1];
const native_handle_t* handle;
uint64_t usage;
void* reserved_proc[8 - (sizeof(uint64_t) / sizeof(void*))];
} ANativeWindowBuffer_t;
typedef struct ANativeWindowBuffer ANativeWindowBuffer;
// Old typedef for backwards compatibility.
typedef ANativeWindowBuffer_t android_native_buffer_t;
ANativeWindowBuffer中，很多属性前面我们介绍Surface时，已经介绍过了。这里重点看看这个native_handle_t。
* system/core/libcutils/include/cutils/native_handle.h
typedef struct native_handle
{
int version; /* sizeof(native_handle_t) */
int numFds; /* number of file-descriptors at &data[0] */
int numInts; /* number of ints at &data[numFds] */
... ...
int data[0]; /* numFds + numInts ints */
... ...
} native_handle_t;
typedef const native_handle_t* buffer_handle_t;
native_handle_t也就是具体Buffer的句柄，根据native_handle_t就能找到护体的Buffer。这里是用文件描述符进行描述的。
GraphicBuffer，很多属性都是继承于父类的，GraphicBuffer自己的属性比较少
* frameworks/native/include/ui/GraphicBuffer.h
uint8_t mOwner;
... ...
GraphicBufferMapper& mBufferMapper;
ssize_t mInitCheck;
// numbers of fds/ints in native_handle_t to flatten
uint32_t mTransportNumFds;
uint32_t mTransportNumInts;
uint64_t mId;
// Stores the generation number of this buffer. If this number does not
// match the BufferQueue's internal generation number (set through
// IGBP::setGenerationNumber), attempts to attach the buffer will fail.
uint32_t mGenerationNumber;
};
- mOwner
表示该GraphicBuffer持有的只是handle，还是持有具体的数据
enum {
ownNone = 0,
ownHandle = 1,
ownData = 2,
};
mOwner不一样，释放时，流程不一样：
void GraphicBuffer::free_handle()
{
if (mOwner == ownHandle) {
mBufferMapper.freeBuffer(handle);
} else if (mOwner == ownData) {
GraphicBufferAllocator& allocator(GraphicBufferAllocator::get());
allocator.free(handle);
}
handle = NULL;
}
-
GraphicBufferMapper
GraphicBuffer实现Flattenable，可以将GraphicBuffer进行打包，在Binder中传递，但是传递只是Buffer的描述属性，并不真正去拷贝Buffer的内容。怎么实现的共享的，关键还是这里的handle。GraphicBufferMapper会根据handle去在不同的进程中进map，map到同一块物理内存。这里先埋个伏笔，后续我们会讲到。 -
mId
GraphicBuffer的ID，这个ID在不同进程中都是一样的 -
mGenerationNumber
可以理解问题这个buffer被用多少次了。如果这个值和BufferQueue中的mGenerationNumber不一直，那么是不能attach的。
余下，GraphicBuffer的相关函数我们接下来具体来看～
分配一块Buffer
Producer dequeueBuffer的时候，并不是 每一次都会去分配一块Buffer。还记得什么时候回去分配Buffer吗？没错，设置了标识BUFFER_NEEDS_REALLOCATION时。
if (returnFlags & BUFFER_NEEDS_REALLOCATION) {
BQ_LOGV("dequeueBuffer: allocating a new buffer for slot %d", *outSlot);
sp<GraphicBuffer> graphicBuffer = new GraphicBuffer(
width, height, format, BQ_LAYER_COUNT, usage,
{mConsumerName.string(), mConsumerName.size()});
此时分配的Buffer，参数比较齐全，对应的构造函数为：
* frameworks/native/libs/ui/GraphicBuffer.cpp
GraphicBuffer::GraphicBuffer(uint32_t inWidth, uint32_t inHeight,
PixelFormat inFormat, uint32_t inLayerCount, uint64_t usage, std::string requestorName)
: GraphicBuffer()
{
mInitCheck = initWithSize(inWidth, inHeight, inFormat, inLayerCount,
usage, std::move(requestorName));
}
在默认构造函数中，主要是做变量是初始化：
GraphicBuffer::GraphicBuffer()
: BASE(), mOwner(ownData), mBufferMapper(GraphicBufferMapper::get()),
mInitCheck(NO_ERROR), mId(getUniqueId()), mGenerationNumber(0)
{
width =
height =
stride =
format =
usage_deprecated = 0;
usage = 0;
layerCount = 0;
handle = NULL;
}
mOwner默认是ownData。GraphicBufferMapper是一个单例类，mBufferMapper在每个进程中只有一个实际对象。inLayerCount为1，在BufferQueueProducer中是一个常量。
static constexpr uint32_t BQ_LAYER_COUNT = 1;
status_t GraphicBuffer::initWithSize(uint32_t inWidth, uint32_t inHeight,
PixelFormat inFormat, uint32_t inLayerCount, uint64_t inUsage,
std::string requestorName)
{
GraphicBufferAllocator& allocator = GraphicBufferAllocator::get();
uint32_t outStride = 0;
status_t err = allocator.allocate(inWidth, inHeight, inFormat, inLayerCount,
inUsage, &handle, &outStride, mId,
std::move(requestorName));
if (err == NO_ERROR) {
mBufferMapper.getTransportSize(handle, &mTransportNumFds, &mTransportNumInts);
width = static_cast<int>(inWidth);
height = static_cast<int>(inHeight);
format = inFormat;
layerCount = inLayerCount;
usage = inUsage;
usage_deprecated = int(usage);
stride = static_cast<int>(outStride);
}
return err;
}
- GraphicBufferAllocator
Buffer管理中，另外一个单例类，GraphicBufferAllocator把Buffer分配出来你，GraphicBufferMapper可以将其map到自己的进程。
需要主要的是，BufferQueueProducer是跑在SurfaceFlinger进程中的，也就是说，绝大部分的应用，使用的Buffer，都是SurfaceFlinger进程分配出来的，所以，如果SurfaceFlinger出现内存泄露，FD泄露等问题，很有可能都是应用没有释放，SurfaceFlinger不会主动释放，它只响应应用的请求。SurfaceFlinger是背锅侠！
GraphicBufferAllocator定义如下：
* frameworks/native/include/ui/GraphicBufferAllocator.h
class GraphicBufferAllocator : public Singleton<GraphicBufferAllocator>
{
public:
static inline GraphicBufferAllocator& get() { return getInstance(); }
status_t allocate(uint32_t w, uint32_t h, PixelFormat format,
uint32_t layerCount, uint64_t usage,
buffer_handle_t* handle, uint32_t* stride, uint64_t graphicBufferId,
std::string requestorName);
status_t free(buffer_handle_t handle);
void dump(String8& res) const;
static void dumpToSystemLog();
private:
struct alloc_rec_t {
uint32_t width;
uint32_t height;
uint32_t stride;
PixelFormat format;
uint32_t layerCount;
uint64_t usage;
size_t size;
std::string requestorName;
};
static Mutex sLock;
static KeyedVector<buffer_handle_t, alloc_rec_t> sAllocList;
friend class Singleton<GraphicBufferAllocator>;
GraphicBufferAllocator();
~GraphicBufferAllocator();
GraphicBufferMapper& mMapper;
const std::unique_ptr<const Gralloc2::Allocator> mAllocator;
};
- 两个主要的方法，一个allocate用来分配Buffer，一个free用来释放Buffe。
- sAllocList，申请的Buffer，都保存下来，放到sAllocList中，并不是保存具体的Buffer，而是Buffer的描述alloc_rec_t。
- mAllocator，Gralloc登场，gralloc采用版本化管理，用的是Gralloc2。
GraphicBufferAllocator的allocate函数如下：
status_t GraphicBufferAllocator::allocate(uint32_t width, uint32_t height,
PixelFormat format, uint32_t layerCount, uint64_t usage,
buffer_handle_t* handle, uint32_t* stride,
uint64_t /*graphicBufferId*/, std::string requestorName)
{
ATRACE_CALL();
// make sure to not allocate a N x 0 or 0 x N buffer, since this is
// allowed from an API stand-point allocate a 1x1 buffer instead.
if (!width || !height)
width = height = 1;
// Ensure that layerCount is valid.
if (layerCount < 1)
layerCount = 1;
Gralloc2::IMapper::BufferDescriptorInfo info = {};
info.width = width;
info.height = height;
info.layerCount = layerCount;
info.format = static_cast<Gralloc2::PixelFormat>(format);
info.usage = usage;
Gralloc2::Error error = mAllocator->allocate(info, stride, handle);
if (error == Gralloc2::Error::NONE) {
Mutex::Autolock _l(sLock);
KeyedVector<buffer_handle_t, alloc_rec_t>& list(sAllocList);
uint32_t bpp = bytesPerPixel(format);
alloc_rec_t rec;
rec.width = width;
rec.height = height;
rec.stride = *stride;
rec.format = format;
rec.layerCount = layerCount;
rec.usage = usage;
rec.size = static_cast<size_t>(height * (*stride) * bpp);
rec.requestorName = std::move(requestorName);
list.add(*handle, rec);
return NO_ERROR;
} else {
ALOGE("Failed to allocate (%u x %u) layerCount %u format %d "
"usage %" PRIx64 ": %d",
width, height, layerCount, format, usage,
error);
return NO_MEMORY;
}
}
在看allocate函数之前，我们先来看一下GraphicBuffer相关的类：
GraphicBuffer关系类图
GraphicBuffer的左膀右臂，GraphicBufferAllocator和GraphicBufferMapper！从Android 8.0开始，Android 操作系统框架在架构方面的一项重大改变，提出了treble 项目。Vendor的实现和Androd的实现分开，Android和HAL，采用HwBinder进行通信，减少Android对HAL的直接依赖。这里的Allocator和Mapper，就是对HAL结合的包装；IAllocator，IMapper的HAL的接口。V2_1::IMapper是一个对Gralloc HAL的2.1版本。
回到allocate函数～
BufferDescriptorInfo，对Buffer的描述，在HAL层也通用。根据需要，生成BufferDescriptorInfo，再通过Gralloc2的Allocator进行allocate。allocate出来的Buffer 句柄，保存在sAllocList中。
Gralloc2 Allocator的allocate函数提供了很多形态，可以满足我们不同的要求：
* frameworks/native/libs/ui/include/ui/Gralloc2.h
/*
* The returned buffers are already imported and must not be imported
* again. outBufferHandles must point to a space that can contain at
* least "count" buffer_handle_t.
*/
Error allocate(BufferDescriptor descriptor, uint32_t count,
uint32_t* outStride, buffer_handle_t* outBufferHandles) const;
Error allocate(BufferDescriptor descriptor,
uint32_t* outStride, buffer_handle_t* outBufferHandle) const
{
return allocate(descriptor, 1, outStride, outBufferHandle);
}
Error allocate(const IMapper::BufferDescriptorInfo& descriptorInfo, uint32_t count,
uint32_t* outStride, buffer_handle_t* outBufferHandles) const
{
BufferDescriptor descriptor;
Error error = mMapper.createDescriptor(descriptorInfo, &descriptor);
if (error == Error::NONE) {
error = allocate(descriptor, count, outStride, outBufferHandles);
}
return error;
}
Error allocate(const IMapper::BufferDescriptorInfo& descriptorInfo,
uint32_t* outStride, buffer_handle_t* outBufferHandle) const
{
return allocate(descriptorInfo, 1, outStride, outBufferHandle);
}
我们传的参数是BufferDescriptorInfo，首先要根据BufferDescriptorInfo，生成一个BufferDescriptor，这个是mapper的HAL层实现的，因为这个BufferDescriptor最后也是要给到HAL层，HAL层根据BufferDescriptor去生成相应描述的Buffer。
最后，allocate的通用实现如下：
* frameworks/native/libs/ui/Gralloc2.cpp
Error Allocator::allocate(BufferDescriptor descriptor, uint32_t count,
uint32_t* outStride, buffer_handle_t* outBufferHandles) const
{
Error error;
auto ret = mAllocator->allocate(descriptor, count,
[&](const auto& tmpError, const auto& tmpStride,
const auto& tmpBuffers) {
error = tmpError;
if (tmpError != Error::NONE) {
return;
}
// import buffers
for (uint32_t i = 0; i < count; i++) {
error = mMapper.importBuffer(tmpBuffers[i],
&outBufferHandles[i]);
if (error != Error::NONE) {
for (uint32_t j = 0; j < i; j++) {
mMapper.freeBuffer(outBufferHandles[j]);
outBufferHandles[j] = nullptr;
}
return;
}
}
*outStride = tmpStride;
});
// make sure the kernel driver sees BC_FREE_BUFFER and closes the fds now
hardware::IPCThreadState::self()->flushCommands();
return (ret.isOk()) ? error : kTransactionError;
}
count，表示需要分配的Buffer个数，也就是说我们一次可以分配多个Buffer。
allocator分配完成后，再通过importBuffer函数，import到我们的handle中outBufferHandle。
* frameworks/native/libs/ui/Gralloc2.cpp
Error Mapper::importBuffer(const hardware::hidl_handle& rawHandle,
buffer_handle_t* outBufferHandle) const
{
Error error;
auto ret = mMapper->importBuffer(rawHandle,
[&](const auto& tmpError, const auto& tmpBuffer)
{
error = tmpError;
if (error != Error::NONE) {
return;
}
*outBufferHandle = static_cast<buffer_handle_t>(tmpBuffer);
});
return (ret.isOk()) ? error : kTransactionError;
}
Gralloc1.0 接口介绍
Graphic相关的HAL的接口都在定义在hardware/interfaces/graphics/。allocator和mapper也是分开的。
IAllocator接口
* hardware/interfaces/graphics/allocator/2.0/IAllocator.hal
package android.hardware.graphics.allocator@2.0;
import android.hardware.graphics.mapper@2.0;
interface IAllocator {
@entry
@exit
@callflow(next="*")
dumpDebugInfo() generates (string debugInfo);
@entry
@exit
@callflow(next="*")
allocate(BufferDescriptor descriptor, uint32_t count)
generates (Error error,
uint32_t stride,
vec<handle> buffers);
};
IAllocator主要两个接口：
-
allocate
根据Buffer Descriptor描述的属性，分配对应的Buffer；count，分配的个数；返回值，stride，Buffer 步长，何为步长？我们知道Buffer都有一个宽度，但是Buffer的内存中分配的时候，都是采用对齐后的大小。多少位对齐，每个硬件平台不一样。比如，我们在一个32对齐的平台上，需要申请一块60x60大小的Buffer。因为要做对齐，所以实际分配的大小为64x60。那么对于这块Buffer，stride就是64。这是因为我们读Buffer的时候，基本都是一行一行的读的，我们要读i行j列，也就是base + i*stride + j的位置。在有的场合下，高也会要求做对齐，那么60x60的Buffer，实际分配的大小是64x64的。buffers这是分配的Buffer的handle了。 -
dumpDebugInfo
dump函数，主要用来debug用
所以，IAllocator的接口主要就一个allocate。
IAllocator又是怎么跟HAL模块连接上的呢？其实一个hidl的接口，在编译时会生成很多东西～
hidl_interface {
name: "android.hardware.graphics.allocator@2.0",
root: "android.hardware",
vndk: {
enabled: true,
},
srcs: [
"IAllocator.hal",
],
interfaces: [
"android.hardware.graphics.common@1.0",
"android.hardware.graphics.mapper@2.0",
"android.hidl.base@1.0",
],
gen_java: false,
}
IAllocator的目录如下：
out/soong/.intermediates/hardware/interfaces/graphics/allocator/2.0
./android.hardware.graphics.allocator@2.0_genc++_headers/gen/android/hardware/graphics/allocator/2.0/IAllocator.h
./android.hardware.graphics.allocator@2.0_genc++/gen/android/hardware/graphics/allocator/2.0/AllocatorAll.cpp
Gralloc2的构造函数中，将首先建立和HAL层的HwBinder服务连接
* frameworks/native/libs/ui/Gralloc2.cpp
Allocator::Allocator(const Mapper& mapper)
: mMapper(mapper)
{
mAllocator = IAllocator::getService();
if (mAllocator == nullptr) {
LOG_ALWAYS_FATAL("gralloc-alloc is missing");
}
}
IAllocator的getService函数，是.hal文件中是没有定义的，但是编译的中间结果中会生成。
* out/soong/.intermediates/hardware/interfaces/graphics/allocator/2.0/android.hardware.graphics.allocator@2.0_genc++_headers/gen/android/hardware/graphics/allocator/2.0/IAllocator.h
static ::android::sp<IAllocator> getService(const std::string &serviceName="default", bool getStub=false);
这里用的是缺省构造函数，这里其实和Binder是类似的：
* out/soong/.intermediates/hardware/interfaces/graphics/allocator/2.0/android.hardware.graphics.allocator@2.0_genc++/gen/android/hardware/graphics/allocator/2.0/AllocatorAll.cpp
// static
::android::sp<IAllocator> IAllocator::getService(const std::string &serviceName, const bool getStub) {
return ::android::hardware::details::getServiceInternal<BpHwAllocator>(serviceName, true, getStub);
}
注册的函数如下：
::android::status_t IAllocator::registerAsService(const std::string &serviceName) {
::android::hardware::details::onRegistration("android.hardware.graphics.allocator@2.0", "IAllocator", serviceName);
const ::android::sp<::android::hidl::manager::V1_0::IServiceManager> sm
= ::android::hardware::defaultServiceManager();
if (sm == nullptr) {
return ::android::INVALID_OPERATION;
}
::android::hardware::Return<bool> ret = sm->add(serviceName.c_str(), this);
return ret.isOk() && ret ? ::android::OK : ::android::UNKNOWN_ERROR;
}
IAllocator HAL服务是谁呢？默认的实现在这里：
hardware/interfaces/graphics/allocator/2.0/default
默认服务起来的时候，将通过defaultPassthroughServiceImplementation去注册IAllocator的HAL服务：
#define LOG_TAG "android.hardware.graphics.allocator@2.0-service"
#include <android/hardware/graphics/allocator/2.0/IAllocator.h>
#include <hidl/LegacySupport.h>
using android::hardware::graphics::allocator::V2_0::IAllocator;
using android::hardware::defaultPassthroughServiceImplementation;
int main() {
return defaultPassthroughServiceImplementation<IAllocator>(4);
}
defaultPassthroughServiceImplementation的实现在LegacySupport.h中
* system/libhidl/transport/include/hidl/LegacySupport.h
template<class Interface>
__attribute__((warn_unused_result))
status_t registerPassthroughServiceImplementation(
std::string name = "default") {
sp<Interface> service = Interface::getService(name, true /* getStub */);
if (service == nullptr) {
ALOGE("Could not get passthrough implementation for %s/%s.",
Interface::descriptor, name.c_str());
return EXIT_FAILURE;
}
LOG_FATAL_IF(service->isRemote(), "Implementation of %s/%s is remote!",
Interface::descriptor, name.c_str());
status_t status = service->registerAsService(name);
if (status == OK) {
ALOGI("Registration complete for %s/%s.",
Interface::descriptor, name.c_str());
} else {
ALOGE("Could not register service %s/%s (%d).",
Interface::descriptor, name.c_str(), status);
}
return status;
}
template<class Interface>
__attribute__((warn_unused_result))
status_t defaultPassthroughServiceImplementation(std::string name,
size_t maxThreads = 1) {
configureRpcThreadpool(maxThreads, true);
status_t result = registerPassthroughServiceImplementation<Interface>(name);
if (result != OK) {
return result;
}
joinRpcThreadpool();
return UNKNOWN_ERROR;
}
template<class Interface>
__attribute__((warn_unused_result))
status_t defaultPassthroughServiceImplementation(size_t maxThreads = 1) {
return defaultPassthroughServiceImplementation<Interface>("default", maxThreads);
}
IAllocator被注册为Passthrough的Service。registerAsService，看看前面的函数，这个service将会被add到IServiceManager中，这这样，get的时候，就能获取到了。
获取到service的时，将会调HIDL_FETCH_***的函数，我们这里就是HIDL_FETCH_IAllocator，中间过程都是在system/libhidl中实现的。这里就不细跟了。
HIDL_FETCH_IAllocator的函数实现如下：
* hardware/interfaces/graphics/allocator/2.0/default/Gralloc.cpp
IAllocator* HIDL_FETCH_IAllocator(const char* /* name */) {
const hw_module_t* module = nullptr;
int err = hw_get_module(GRALLOC_HARDWARE_MODULE_ID, &module);
if (err) {
ALOGE("failed to get gralloc module");
return nullptr;
}
uint8_t major = (module->module_api_version >> 8) & 0xff;
switch (major) {
case 1:
return new Gralloc1Allocator(module);
case 0:
return new Gralloc0Allocator(module);
default:
ALOGE("unknown gralloc module major version %d", major);
return nullptr;
}
}
HIDL_FETCH时，将会加载对应的HAL实现了。gralloc这边的HAL实现GRALLOC_HARDWARE_MODULE_ID。major就是gralloc的API版本。Gralloc1Allocator是对1.0版本的适配，Gralloc0Allocator是对最初版本的适配。
Gralloc1 Allocator HAL层接口
大多数Hardware的接口都定义在hardware/libhardware/include/hardware，Gralloc也不例外。
Gralloc1，HAL的描述为gralloc1_device_t
* hardware/libhardware/include/hardware/gralloc1.h
typedef struct gralloc1_device {
/* Must be the first member of this struct, since a pointer to this struct
* will be generated by casting from a hw_device_t* */
struct hw_device_t common;
// 获取Devices支持的能力
void (*getCapabilities)(struct gralloc1_device* device, uint32_t* outCount,
int32_t* /*gralloc1_capability_t*/ outCapabilities);
// 获取对应功能的函数指针
gralloc1_function_pointer_t (*getFunction)(struct gralloc1_device* device,
int32_t /*gralloc1_function_descriptor_t*/ descriptor);
} gralloc1_device_t;
Gralloc1和前面的的实现有比较大的差别，接口都通过函数指针实现，不再采用原来的方式。
下面是Gralloc0的定义：
* hardware/libhardware/include/hardware/gralloc.h
typedef struct alloc_device_t {
struct hw_device_t common;
int (*alloc)(struct alloc_device_t* dev,
int w, int h, int format, int usage,
buffer_handle_t* handle, int* stride);
int (*free)(struct alloc_device_t* dev,
buffer_handle_t handle);
void (*dump)(struct alloc_device_t *dev, char *buff, int buff_len);
void* reserved_proc[7];
} alloc_device_t;
Gralloc0中，还是采用直接的函数调用。Gralloc1中，只是getCapabilities采用直接的函数调用。
Gralloc1时，走的Gralloc1Allocator，Gralloc0时，走的Gralloc0Allocator。我们主要来看一下Gralloc1Allocator。
* hardware/interfaces/graphics/allocator/2.0/default/Gralloc1Allocator.cpp
Gralloc1Allocator::Gralloc1Allocator(const hw_module_t* module)
: mDevice(nullptr), mCapabilities(), mDispatch() {
int result = gralloc1_open(module, &mDevice);
if (result) {
LOG_ALWAYS_FATAL("failed to open gralloc1 device: %s",
strerror(-result));
}
initCapabilities();
initDispatch();
}
gralloc1_open，打开HAL层Gralloc1的具体实现。获取到gralloc1_device_t设备mDevice。
通过initCapabilities函数，将Gralloc1的能力都读出来，放到capabilities中
* hardware/interfaces/graphics/allocator/2.0/default/Gralloc1Allocator.cpp
void Gralloc1Allocator::initCapabilities() {
uint32_t count = 0;
mDevice->getCapabilities(mDevice, &count, nullptr);
std::vector<int32_t> capabilities(count);
mDevice->getCapabilities(mDevice, &count, capabilities.data());
capabilities.resize(count);
for (auto capability : capabilities) {
if (capability == GRALLOC1_CAPABILITY_LAYERED_BUFFERS) {
mCapabilities.layeredBuffers = true;
break;
}
}
}
mDevice的getCapabilities函数调了两次，这个在HAL实现中经常用到，第一次，主要是获取大小，第二次才去获取具体的值。
initDispatch初始化函数指针，
* hardware/interfaces/graphics/allocator/2.0/default/Gralloc1Allocator.cpp
template <typename T>
void Gralloc1Allocator::initDispatch(gralloc1_function_descriptor_t desc,
T* outPfn) {
auto pfn = mDevice->getFunction(mDevice, desc);
if (!pfn) {
LOG_ALWAYS_FATAL("failed to get gralloc1 function %d", desc);
}
*outPfn = reinterpret_cast<T>(pfn);
}
void Gralloc1Allocator::initDispatch() {
initDispatch(GRALLOC1_FUNCTION_DUMP, &mDispatch.dump);
initDispatch(GRALLOC1_FUNCTION_CREATE_DESCRIPTOR,
&mDispatch.createDescriptor);
initDispatch(GRALLOC1_FUNCTION_DESTROY_DESCRIPTOR,
&mDispatch.destroyDescriptor);
initDispatch(GRALLOC1_FUNCTION_SET_DIMENSIONS, &mDispatch.setDimensions);
initDispatch(GRALLOC1_FUNCTION_SET_FORMAT, &mDispatch.setFormat);
if (mCapabilities.layeredBuffers) {
initDispatch(GRALLOC1_FUNCTION_SET_LAYER_COUNT,
&mDispatch.setLayerCount);
}
initDispatch(GRALLOC1_FUNCTION_SET_CONSUMER_USAGE,
&mDispatch.setConsumerUsage);
initDispatch(GRALLOC1_FUNCTION_SET_PRODUCER_USAGE,
&mDispatch.setProducerUsage);
initDispatch(GRALLOC1_FUNCTION_GET_STRIDE, &mDispatch.getStride);
initDispatch(GRALLOC1_FUNCTION_ALLOCATE, &mDispatch.allocate);
initDispatch(GRALLOC1_FUNCTION_RELEASE, &mDispatch.release);
}
mDevice根据gralloc1_function_descriptor_t，去HAL的实现中去获取对应的函数指针，初始化到mDispatch中。以后我们直接调mDispatch中的函数就访问到HAL的实现。
Gralloc1的gralloc1_function_descriptor_t包括：
* hardware/libhardware/include/hardware/gralloc1.h
typedef enum {
GRALLOC1_FUNCTION_INVALID = 0,
GRALLOC1_FUNCTION_DUMP = 1,
GRALLOC1_FUNCTION_CREATE_DESCRIPTOR = 2,
GRALLOC1_FUNCTION_DESTROY_DESCRIPTOR = 3,
GRALLOC1_FUNCTION_SET_CONSUMER_USAGE = 4,
GRALLOC1_FUNCTION_SET_DIMENSIONS = 5,
GRALLOC1_FUNCTION_SET_FORMAT = 6,
GRALLOC1_FUNCTION_SET_PRODUCER_USAGE = 7,
GRALLOC1_FUNCTION_GET_BACKING_STORE = 8,
GRALLOC1_FUNCTION_GET_CONSUMER_USAGE = 9,
GRALLOC1_FUNCTION_GET_DIMENSIONS = 10,
GRALLOC1_FUNCTION_GET_FORMAT = 11,
GRALLOC1_FUNCTION_GET_PRODUCER_USAGE = 12,
GRALLOC1_FUNCTION_GET_STRIDE = 13,
GRALLOC1_FUNCTION_ALLOCATE = 14,
GRALLOC1_FUNCTION_RETAIN = 15,
GRALLOC1_FUNCTION_RELEASE = 16,
GRALLOC1_FUNCTION_GET_NUM_FLEX_PLANES = 17,
GRALLOC1_FUNCTION_LOCK = 18,
GRALLOC1_FUNCTION_LOCK_FLEX = 19,
GRALLOC1_FUNCTION_UNLOCK = 20,
GRALLOC1_FUNCTION_SET_LAYER_COUNT = 21,
GRALLOC1_FUNCTION_GET_LAYER_COUNT = 22,
GRALLOC1_LAST_FUNCTION = 22,
} gralloc1_function_descriptor_t;
IAllocator需要实现的gralloc1_function_descriptor_t包括：
* hardware/interfaces/graphics/allocator/2.0/default/Gralloc1Allocator.h
struct {
GRALLOC1_PFN_DUMP dump;
GRALLOC1_PFN_CREATE_DESCRIPTOR createDescriptor;
GRALLOC1_PFN_DESTROY_DESCRIPTOR destroyDescriptor;
GRALLOC1_PFN_SET_DIMENSIONS setDimensions;
GRALLOC1_PFN_SET_FORMAT setFormat;
GRALLOC1_PFN_SET_LAYER_COUNT setLayerCount;
GRALLOC1_PFN_SET_CONSUMER_USAGE setConsumerUsage;
GRALLOC1_PFN_SET_PRODUCER_USAGE setProducerUsage;
GRALLOC1_PFN_GET_STRIDE getStride;
GRALLOC1_PFN_ALLOCATE allocate;
GRALLOC1_PFN_RELEASE release;
} mDispatch;
我们去实现Gralloc1的HAL时，allocator只去要实现getCapabilities和上面mDispatch中的gralloc1_function_descriptor_t就可以了。
IMapper接口
IMapper的接口有两个版本2.0和2.1：
ls hardware/interfaces/graphics/mapper
2.0 2.1
2.1是可选的，暂时不严格要求支持：
* frameworks/native/libs/ui/Gralloc2.cpp
void Mapper::preload() {
android::hardware::preloadPassthroughService<hardware::graphics::mapper::V2_0::IMapper>();
}
Mapper::Mapper()
{
mMapper = IMapper::getService();
if (mMapper == nullptr) {
LOG_ALWAYS_FATAL("gralloc-mapper is missing");
}
if (mMapper->isRemote()) {
LOG_ALWAYS_FATAL("gralloc-mapper must be in passthrough mode");
}
// IMapper 2.1 is optional
mMapperV2_1 = hardware::graphics::mapper::V2_1::IMapper::castFrom(mMapper);
}
IMapper也是PassThrough的模式。
IMapper2.0的接口
* hardware/interfaces/graphics/mapper/2.0/IMapper.hal
package android.hardware.graphics.mapper@2.0;
import android.hardware.graphics.common@1.0;
interface IMapper {
struct BufferDescriptorInfo {
uint32_t width; // 宽，横向的像素点数
uint32_t height; //高，纵向的像素点数
/**
* The number of image layers that must be in the allocated buffer.
*/
uint32_t layerCount;
PixelFormat format; //像素点的格式
bitfield<BufferUsage> usage; //用处
};
struct Rect {
int32_t left;
int32_t top;
int32_t width;
int32_t height;
};
/**
* 创建一个Buffer的描述，这个描述在分配Buffer时使用
* 如果成功，返回值为NONE, 参数无效或冲突返回BAD_VALUE，没有资源返回NO_RESOURCES，参数不支持返回UNSUPPORTED
*/
@entry
@callflow(next="*")
createDescriptor(BufferDescriptorInfo descriptorInfo)
generates (Error error,
BufferDescriptor descriptor);
@entry
@callflow(next="*")
importBuffer(handle rawHandle) generates (Error error, pointer buffer);
@exit
@callflow(next="*")
freeBuffer(pointer buffer) generates (Error error);
@callflow(next="unlock")
lock(pointer buffer,
bitfield<BufferUsage> cpuUsage,
Rect accessRegion,
handle acquireFence)
generates (Error error,
pointer data);
@callflow(next="unlock")
lockYCbCr(pointer buffer,
bitfield<BufferUsage> cpuUsage,
Rect accessRegion,
handle acquireFence)
generates (Error error,
YCbCrLayout layout);
@callflow(next="*")
unlock(pointer buffer)
generates (Error error,
handle releaseFence);
};
IMapper的接口比IAllocator多，具体一些信息我写在代码中。
-
createDescriptor
创建一个BufferDescriptor，分配Buffer时，根据Descriptor分配。 -
importBuffer
Buffer被冲其他进程或HAL克隆出来时，这个Buffer是RAW状态的Buffer，raw handle是不能直接访问真正的Buffer的，我们需要把它imported到imported的handle中才能访问。创建imported handle时，需要验证raw handle的有效性，且raw handle需要能多少import创建多个imported handle。在passthrough HALs中，从HAL接收到的handle，可能已经被import到进程中，这个时候要能区分，将其当做raw handle处理，而不是返回BAD_BUFFER。 -
freeBuffer
释放Buffer handle，通过importBuffer返回的handle必现通过这个接口释放。importBuffer时申请的所有资源必须一起释放。比如 imported handle如果通过native_handle_create创建的，那么必须调用native_handle_close和native_handle_delete -
lock
将Buffer锁住，用来做制定的处理。多线程可以同事lock，但是不能同时写。超出accessRegion区域的Buffer不能写，超出的区域不受保护。Buffer的地址是指针buffer，是从left-top开始的，即使accessRegion不是left-top描述。 -
lockYCbCr
这个lock很相似，只是返回值不一样，这里是YCbCrLayout。除非是Codec配置为flexible-YUV-compatible的颜色格式，要不必现是PixelFormat::YCbCr_*_888格式的。 -
unlock
表示CPU访问Buffer已经完成
IMapper用到的数据类型定义在types.hal中
* hardware/interfaces/graphics/mapper/2.0/types.hal
package android.hardware.graphics.mapper@2.0;
enum Error : int32_t {
NONE = 0, /** no error */
BAD_DESCRIPTOR = 1, /** invalid BufferDescriptor */
BAD_BUFFER = 2, /** invalid buffer handle */
BAD_VALUE = 3, /** invalid width, height, etc. */
/* 4 is reserved */
NO_RESOURCES = 5, /** temporary failure due to resource contention */
/* 6 is reserved */
UNSUPPORTED = 7, /** permanent failure */
};
/**
* A buffer descriptor is an implementation-defined opaque data returned by
* createDescriptor. It describes the properties of a buffer and is consumed
* by the allocator.
*/
typedef vec<uint32_t> BufferDescriptor;
/**
* Structure for describing YCbCr formats for consumption by applications.
* This is used with PixelFormat::YCBCR_*_888.
*
* Buffer chroma subsampling is defined in the format.
* e.g. PixelFormat::YCBCR_420_888 has subsampling 4:2:0.
*
* Buffers must have a 8 bit depth.
*
* y, cb, and cr point to the first byte of their respective planes.
*
* Stride describes the distance in bytes from the first value of one row of
* the image to the first value of the next row. It includes the width of the
* image plus padding.
* yStride is the stride of the luma plane.
* cStride is the stride of the chroma planes.
*
* chromaStep is the distance in bytes from one chroma pixel value to the
* next. This is 2 bytes for semiplanar (because chroma values are interleaved
* and each chroma value is one byte) and 1 for planar.
*/
struct YCbCrLayout {
pointer y;
pointer cb;
pointer cr;
uint32_t yStride;
uint32_t cStride;
uint32_t chromaStep;
};
IMapper2.1的接口
IMapper2.1的接口继承IMapper2.0的接口：
* hardware/interfaces/graphics/mapper/2.1/IMapper.hal
package android.hardware.graphics.mapper@2.1;
import android.hardware.graphics.mapper@2.0::Error;
import android.hardware.graphics.mapper@2.0::IMapper;
interface IMapper extends android.hardware.graphics.mapper@2.0::IMapper {
validateBufferSize(pointer buffer,
BufferDescriptorInfo descriptorInfo,
uint32_t stride)
generates (Error error);
/**
* Get the transport size of a buffer. An imported buffer handle is a raw
* buffer handle with the process-local runtime data appended. This
* function, for example, allows a caller to omit the process-local
* runtime data at the tail when serializing the imported buffer handle.
*
* Note that a client might or might not omit the process-local runtime
* data when sending an imported buffer handle. The mapper must support
* both cases on the receiving end.
*
* @param buffer is the buffer to get the transport size from.
* @return error is NONE upon success. Otherwise,
* BAD_BUFFER when the buffer is invalid.
* @return numFds is the number of file descriptors needed for transport.
* @return numInts is the number of integers needed for transport.
*/
getTransportSize(pointer buffer)
generates (Error error,
uint32_t numFds,
uint32_t numInts);
};
-
validateBufferSize
验证，Buffer能不能被制定的描述信息和步长的访问者访问。 -
getTransportSize
获取Buffer传输的大小。一个Imported handle是一个raw handle再加上进程本地运行的数据，所以我们可以获取到进程本地的数据。
IMapper的HIDL_FETCH_IMapper函数实现如下：
* hardware/interfaces/graphics/mapper/2.0/default/GrallocMapper.cpp
IMapper* HIDL_FETCH_IMapper(const char* /* name */) {
const hw_module_t* module = nullptr;
int err = hw_get_module(GRALLOC_HARDWARE_MODULE_ID, &module);
if (err) {
ALOGE("failed to get gralloc module");
return nullptr;
}
uint8_t major = (module->module_api_version >> 8) & 0xff;
switch (major) {
case 1:
return new Gralloc1Mapper(module);
case 0:
return new Gralloc0Mapper(module);
default:
ALOGE("unknown gralloc module major version %d", major);
return nullptr;
}
}
IMapper的HAL模块ID为GRALLOC_HARDWARE_MODULE_ID，和IAllocator类似，这里也对应两个mapper。Gralloc1Mapper和Gralloc0Mapper
前面IAllocator的时候，有个main函数，这里为什么没有？那么，IMapper是怎么找到的呢？
夏雨荷已死，还记得Gralloc2中的preload吗？
* frameworks/native/libs/ui/Gralloc2.cpp
void Mapper::preload() {
android::hardware::preloadPassthroughService<hardware::graphics::mapper::V2_0::IMapper>();
}
Gralloc1 Mapper HAL层接口
Mapper的接口也定义在gralloc1.h中，Gralloc1对应的Mapper为Gralloc1Mapper
* hardware/interfaces/graphics/allocator/2.0/default/Gralloc1On0Adapter.cpp
Gralloc1Mapper::Gralloc1Mapper(const hw_module_t* module)
: mDevice(nullptr), mDispatch() {
int result = gralloc1_open(module, &mDevice);
if (result) {
LOG_ALWAYS_FATAL("failed to open gralloc1 device: %s",
strerror(-result));
}
initCapabilities();
initDispatch();
}
mapper的initCapabilities函数，和allocator的initCapabilities函数类似，都是通过gralloc1_device_t的getCapabilities函数去获取。只是这里但是做了一个封装了mCapabilities。
void Gralloc1Mapper::initCapabilities() {
mCapabilities.highUsageBits = true;
mCapabilities.layeredBuffers = false;
mCapabilities.unregisterImplyDelete = false;
uint32_t count = 0;
mDevice->getCapabilities(mDevice, &count, nullptr);
std::vector<int32_t> capabilities(count);
mDevice->getCapabilities(mDevice, &count, capabilities.data());
capabilities.resize(count);
for (auto capability : capabilities) {
switch (capability) {
case GRALLOC1_CAPABILITY_LAYERED_BUFFERS:
mCapabilities.layeredBuffers = true;
break;
case GRALLOC1_CAPABILITY_RELEASE_IMPLY_DELETE:
mCapabilities.unregisterImplyDelete = true;
break;
}
}
}
只是这里但是做了一个封装了mCapabilities。
struct {
bool highUsageBits;
bool layeredBuffers;
bool unregisterImplyDelete;
} mCapabilities = {};
Gralloc1，中Mapper 对应的gralloc1_function_descriptor_t如下：
template <typename T>
void Gralloc1Mapper::initDispatch(gralloc1_function_descriptor_t desc,
T* outPfn) {
auto pfn = mDevice->getFunction(mDevice, desc);
if (!pfn) {
LOG_ALWAYS_FATAL("failed to get gralloc1 function %d", desc);
}
*outPfn = reinterpret_cast<T>(pfn);
}
void Gralloc1Mapper::initDispatch() {
initDispatch(GRALLOC1_FUNCTION_RETAIN, &mDispatch.retain);
initDispatch(GRALLOC1_FUNCTION_RELEASE, &mDispatch.release);
initDispatch(GRALLOC1_FUNCTION_GET_NUM_FLEX_PLANES,
&mDispatch.getNumFlexPlanes);
initDispatch(GRALLOC1_FUNCTION_LOCK, &mDispatch.lock);
initDispatch(GRALLOC1_FUNCTION_LOCK_FLEX, &mDispatch.lockFlex);
initDispatch(GRALLOC1_FUNCTION_UNLOCK, &mDispatch.unlock);
}
mapper的HAL实现，只要实现上述的gralloc1_function_descriptor_t。
我们来看一下Gralloc1的相关类似关系～
gralloc1关系类图
最终，Gralloc1都是在gralloc1_device_t中去实现的。当然，如果HAL没有实现对应地Gralloc1，而是Gralloc0。Android这边也是提供适配的。对应的代码在：
hardware/interfaces/graphics/allocator/2.0/default/gralloc1-adapter.cpp
下面，我们找一个具体平台的实现来看看，gralloc的HAL层是怎么实现的。
Qcom高通平台Gralloc HAL实现
我们这里拿到的代码是AOSP的，和vendor从Qcom那里拿到的估计有些区别。我们就看骁龙835吧～，msm8998的displayHAL相关的实现在hardware/qcom/display/msm8998。
gralloc1整体架构
高通gralloc HAL的实现在libgralloc1中
* hardware/qcom/display/msm8998/libgralloc1/gr_device_impl.cpp
static struct hw_module_methods_t gralloc_module_methods = {.open = gralloc_device_open};
struct gralloc_module_t HAL_MODULE_INFO_SYM = {
.common = {
.tag = HARDWARE_MODULE_TAG,
.module_api_version = GRALLOC_MODULE_API_VERSION_1_0,
.hal_api_version = HARDWARE_HAL_API_VERSION,
.id = GRALLOC_HARDWARE_MODULE_ID,
.name = "Graphics Memory Module",
.author = "Code Aurora Forum",
.methods = &gralloc_module_methods,
.dso = 0,
.reserved = {0},
},
};
int gralloc_device_open(const struct hw_module_t *module, const char *name, hw_device_t **device) {
int status = -EINVAL;
if (!strcmp(name, GRALLOC_HARDWARE_MODULE_ID)) {
gralloc1::GrallocImpl * /*gralloc1_device_t*/ dev = gralloc1::GrallocImpl::GetInstance(module);
*device = reinterpret_cast<hw_device_t *>(dev);
if (dev) {
status = 0;
} else {
ALOGE("Fatal error opening gralloc1 device");
}
}
return status;
}
Qcom 的gralloc是1.0版本～采用C++编写，具体实现的类为 GrallocImpl。GrallocImpl继承gralloc1_device_t。
GrallocImpl::GrallocImpl(const hw_module_t *module) {
common.tag = HARDWARE_DEVICE_TAG;
common.version = GRALLOC_MODULE_API_VERSION_1_0;
common.module = const_cast<hw_module_t *>(module);
common.close = CloseDevice;
getFunction = GetFunction;
getCapabilities = GetCapabilities;
initalized_ = Init();
}
gralloc1_device_t的getFunction初始化为GetFunction，getCapabilities初始化为GetCapabilities。
而在Init，申请了一个BufferManager。BufferManager是单例的用法。GrallocImpl也是单例的用法。
bool GrallocImpl::Init() {
buf_mgr_ = BufferManager::GetInstance();
return buf_mgr_ != nullptr;
}
Qcom的Gralloc1支持 Capabilities 有3种：
void GrallocImpl::GetCapabilities(struct gralloc1_device *device, uint32_t *out_count,
int32_t /*gralloc1_capability_t*/ *out_capabilities) {
if (device != nullptr) {
if (out_capabilities != nullptr && *out_count >= 3) {
out_capabilities[0] = GRALLOC1_CAPABILITY_TEST_ALLOCATE;
out_capabilities[1] = GRALLOC1_CAPABILITY_LAYERED_BUFFERS;
out_capabilities[2] = GRALLOC1_CAPABILITY_RELEASE_IMPLY_DELETE;
}
*out_count = 3;
}
return;
}
从Android对Capabilities的定义来看，Qcom Gralloc1支持Android要求的所有能力。
* hardware/libhardware/include/hardware/gralloc1.h
typedef enum {
GRALLOC1_CAPABILITY_INVALID = 0,
/* If this capability is supported, then the outBuffers parameter to
* allocate may be NULL, which instructs the device to report whether the
* given allocation is possible or not. */
GRALLOC1_CAPABILITY_TEST_ALLOCATE = 1,
/* If this capability is supported, then the implementation supports
* allocating buffers with more than one image layer. */
GRALLOC1_CAPABILITY_LAYERED_BUFFERS = 2,
/* If this capability is supported, then the implementation always closes
* and deletes a buffer handle whenever the last reference is removed.
*
* Supporting this capability is strongly recommended. It will become
* mandatory in future releases. */
GRALLOC1_CAPABILITY_RELEASE_IMPLY_DELETE = 3,
GRALLOC1_LAST_CAPABILITY = 3,
} gralloc1_capability_t;
GetFunction函数，初始化函数指针，gralloc1_function_descriptor_t对应的指针实现如下：
gralloc1_function_pointer_t GrallocImpl::GetFunction(gralloc1_device_t *device, int32_t function) {
if (!device) {
return NULL;
}
switch (function) {
case GRALLOC1_FUNCTION_DUMP:
return reinterpret_cast<gralloc1_function_pointer_t>(Dump);
case GRALLOC1_FUNCTION_CREATE_DESCRIPTOR:
return reinterpret_cast<gralloc1_function_pointer_t>(CreateBufferDescriptor);
case GRALLOC1_FUNCTION_DESTROY_DESCRIPTOR:
return reinterpret_cast<gralloc1_function_pointer_t>(DestroyBufferDescriptor);
case GRALLOC1_FUNCTION_SET_CONSUMER_USAGE:
return reinterpret_cast<gralloc1_function_pointer_t>(SetConsumerUsage);
case GRALLOC1_FUNCTION_SET_DIMENSIONS:
return reinterpret_cast<gralloc1_function_pointer_t>(SetBufferDimensions);
case GRALLOC1_FUNCTION_SET_FORMAT:
return reinterpret_cast<gralloc1_function_pointer_t>(SetColorFormat);
case GRALLOC1_FUNCTION_SET_LAYER_COUNT:
return reinterpret_cast<gralloc1_function_pointer_t>(SetLayerCount);
case GRALLOC1_FUNCTION_SET_PRODUCER_USAGE:
return reinterpret_cast<gralloc1_function_pointer_t>(SetProducerUsage);
case GRALLOC1_FUNCTION_GET_BACKING_STORE:
return reinterpret_cast<gralloc1_function_pointer_t>(GetBackingStore);
case GRALLOC1_FUNCTION_GET_CONSUMER_USAGE:
return reinterpret_cast<gralloc1_function_pointer_t>(GetConsumerUsage);
case GRALLOC1_FUNCTION_GET_DIMENSIONS:
return reinterpret_cast<gralloc1_function_pointer_t>(GetBufferDimensions);
case GRALLOC1_FUNCTION_GET_FORMAT:
return reinterpret_cast<gralloc1_function_pointer_t>(GetColorFormat);
case GRALLOC1_FUNCTION_GET_LAYER_COUNT:
return reinterpret_cast<gralloc1_function_pointer_t>(GetLayerCount);
case GRALLOC1_FUNCTION_GET_PRODUCER_USAGE:
return reinterpret_cast<gralloc1_function_pointer_t>(GetProducerUsage);
case GRALLOC1_FUNCTION_GET_STRIDE:
return reinterpret_cast<gralloc1_function_pointer_t>(GetBufferStride);
case GRALLOC1_FUNCTION_ALLOCATE:
return reinterpret_cast<gralloc1_function_pointer_t>(AllocateBuffers);
case GRALLOC1_FUNCTION_RETAIN:
return reinterpret_cast<gralloc1_function_pointer_t>(RetainBuffer);
case GRALLOC1_FUNCTION_RELEASE:
return reinterpret_cast<gralloc1_function_pointer_t>(ReleaseBuffer);
case GRALLOC1_FUNCTION_GET_NUM_FLEX_PLANES:
return reinterpret_cast<gralloc1_function_pointer_t>(GetNumFlexPlanes);
case GRALLOC1_FUNCTION_LOCK:
return reinterpret_cast<gralloc1_function_pointer_t>(LockBuffer);
case GRALLOC1_FUNCTION_LOCK_FLEX:
return reinterpret_cast<gralloc1_function_pointer_t>(LockFlex);
case GRALLOC1_FUNCTION_UNLOCK:
return reinterpret_cast<gralloc1_function_pointer_t>(UnlockBuffer);
case GRALLOC1_FUNCTION_PERFORM:
return reinterpret_cast<gralloc1_function_pointer_t>(Gralloc1Perform);
default:
ALOGE("%s:Gralloc Error. Client Requested for unsupported function", __FUNCTION__);
return NULL;
}
return NULL;
}
来看看Qcom Gralloc1的整体架构～
高通gralloc1关系类图
- GrallocImpl继承gralloc1_device_t，这个Gralloc1具体的实现！
- GrallocImpl采用一个BufferManager，管理Buffer，自己当领导！
- BufferManager，抽像了一个Allocator，负责具体的Buffer分配！
- Allocator说，我不具体干活，这个活外包给IonAlloc干，IonAlloc好好干，干不好，给就给别人来做了。
- IonAlloc采用ion Buffer，负责具体的Buffer处理
总的来说，设计清晰，扩展方便～
allocate相关流程
我们来看下allocate Buffer的流程，代码就不贴了，给个流程图吧～
gralloc1的allocate流程
这个流程图中，包括了release的流程～
Android中的importBuffer函数，在default中变为registerBuffer，在HAL中变成retain，高通对应的实现为RetainBuffer，IonAlloc中又变为ImportBuffer。（...不止72变了...比孙悟空还厉害）
* hardware/qcom/display/msm8998/libgralloc1/gr_ion_alloc.cpp
int IonAlloc::ImportBuffer(int fd) {
struct ion_fd_data fd_data;
int err = 0;
fd_data.fd = fd;
if (ioctl(ion_dev_fd_, INT(ION_IOC_IMPORT), &fd_data)) {
err = -errno;
ALOGE("%s: ION_IOC_IMPORT failed with error - %s", __FUNCTION__, strerror(errno));
return err;
}
return fd_data.handle;
}
import对应的ioctl为ION_IOC_IMPORT。
ion相关的定义，Android有标准的要求，可以参考：
* system/core/libion/original-kernel-headers/linux/ion.h
#ifndef _UAPI_LINUX_ION_H
#define _UAPI_LINUX_ION_H
#include <linux/ioctl.h>
#include <linux/types.h>
typedef int ion_user_handle_t;
enum ion_heap_type {
ION_HEAP_TYPE_SYSTEM,
ION_HEAP_TYPE_SYSTEM_CONTIG,
ION_HEAP_TYPE_CARVEOUT,
ION_HEAP_TYPE_CHUNK,
ION_HEAP_TYPE_DMA,
ION_HEAP_TYPE_CUSTOM, /* must be last so device specific heaps always
are at the end of this enum */
ION_NUM_HEAPS = 16,
};
#define ION_HEAP_SYSTEM_MASK (1 << ION_HEAP_TYPE_SYSTEM)
#define ION_HEAP_SYSTEM_CONTIG_MASK (1 << ION_HEAP_TYPE_SYSTEM_CONTIG)
#define ION_HEAP_CARVEOUT_MASK (1 << ION_HEAP_TYPE_CARVEOUT)
#define ION_HEAP_TYPE_DMA_MASK (1 << ION_HEAP_TYPE_DMA)
#define ION_NUM_HEAP_IDS sizeof(unsigned int) * 8
#define ION_FLAG_CACHED 1 /* mappings of this buffer should be
cached, ion will do cache
maintenance when the buffer is
mapped for dma */
#define ION_FLAG_CACHED_NEEDS_SYNC 2 /* mappings of this buffer will created
at mmap time, if this is set
caches must be managed manually */
struct ion_allocation_data {
size_t len;
size_t align;
unsigned int heap_id_mask;
unsigned int flags;
ion_user_handle_t handle;
};
struct ion_fd_data {
ion_user_handle_t handle;
int fd;
};
struct ion_handle_data {
ion_user_handle_t handle;
};
struct ion_custom_data {
unsigned int cmd;
unsigned long arg;
};
#define ION_IOC_MAGIC 'I'
#define ION_IOC_ALLOC _IOWR(ION_IOC_MAGIC, 0, \
struct ion_allocation_data)
#define ION_IOC_FREE _IOWR(ION_IOC_MAGIC, 1, struct ion_handle_data)
#define ION_IOC_MAP _IOWR(ION_IOC_MAGIC, 2, struct ion_fd_data)
#define ION_IOC_SHARE _IOWR(ION_IOC_MAGIC, 4, struct ion_fd_data)
#define ION_IOC_IMPORT _IOWR(ION_IOC_MAGIC, 5, struct ion_fd_data)
#define ION_IOC_SYNC _IOWR(ION_IOC_MAGIC, 7, struct ion_fd_data)
#define ION_IOC_CUSTOM _IOWR(ION_IOC_MAGIC, 6, struct ion_custom_data)
#endif /* _UAPI_LINUX_ION_H */
Qcom对应的定义在msm_ion.h中，msm_ion.h在这里就不看了。
Buffer的usage处理
usage分为两类，一个是Producer的，一个是Consumer的。在GetIonHeapInfo中对usage进行了处理。转换为ion对应的描述ion_heap_id，alloc_type以及ion_flags。这三个属性上面的头文件中有定义。usage的转换如下：
* hardware/qcom/display/msm8998/libgralloc1/gr_allocator.cpp
void Allocator::GetIonHeapInfo(gralloc1_producer_usage_t prod_usage,
gralloc1_consumer_usage_t cons_usage, unsigned int *ion_heap_id,
unsigned int *alloc_type, unsigned int *ion_flags) {
unsigned int heap_id = 0;
unsigned int type = 0;
uint32_t flags = 0;
if (prod_usage & GRALLOC1_PRODUCER_USAGE_PROTECTED) {
if (cons_usage & GRALLOC1_CONSUMER_USAGE_PRIVATE_SECURE_DISPLAY) {
heap_id = ION_HEAP(SD_HEAP_ID);
/*
* There is currently no flag in ION for Secure Display
* VM. Please add it to the define once available.
*/
flags |= UINT(ION_SD_FLAGS);
} else if (prod_usage & GRALLOC1_PRODUCER_USAGE_CAMERA) {
heap_id = ION_HEAP(SD_HEAP_ID);
if (cons_usage & GRALLOC1_CONSUMER_USAGE_HWCOMPOSER) {
flags |= UINT(ION_SC_PREVIEW_FLAGS);
} else {
flags |= UINT(ION_SC_FLAGS);
}
} else {
heap_id = ION_HEAP(CP_HEAP_ID);
flags |= UINT(ION_CP_FLAGS);
}
} else if (prod_usage & GRALLOC1_PRODUCER_USAGE_PRIVATE_MM_HEAP) {
// MM Heap is exclusively a secure heap.
// If it is used for non secure cases, fallback to IOMMU heap
ALOGW("MM_HEAP cannot be used as an insecure heap. Using system heap instead!!");
heap_id |= ION_HEAP(ION_SYSTEM_HEAP_ID);
}
if (prod_usage & GRALLOC1_PRODUCER_USAGE_PRIVATE_CAMERA_HEAP) {
heap_id |= ION_HEAP(ION_CAMERA_HEAP_ID);
}
if (prod_usage & GRALLOC1_PRODUCER_USAGE_PRIVATE_ADSP_HEAP ||
prod_usage & GRALLOC1_PRODUCER_USAGE_SENSOR_DIRECT_DATA) {
heap_id |= ION_HEAP(ION_ADSP_HEAP_ID);
}
if (flags & UINT(ION_SECURE)) {
type |= private_handle_t::PRIV_FLAGS_SECURE_BUFFER;
}
// if no ion heap flags are set, default to system heap
if (!heap_id) {
heap_id = ION_HEAP(ION_SYSTEM_HEAP_ID);
}
*alloc_type = type;
*ion_flags = flags;
*ion_heap_id = heap_id;
return;
}
Qcom的Gralloc1就不多介绍了，需要注意的是Qcom对很多数据结构进行封装，增加了更多的信息，可以借助Qcom的文档进行理解。比如private_handle_t继承native_handle_t，对native_handle_t进行了扩展。定义在下面的头文件中。
hardware/qcom/display/msm8998/libgralloc1/gr_priv_handle.h
ION Buffer
Ion Buffer是一种内存分配器，是Android 4.0版本开始引入的，用以取代被诟病的PMEM，完美解决内存碎片管理。Ion管理着一个或多个内存池，其中有一些会在启动的时候预先分配，供一些特殊的设备使用，比如GPU，Display。
IonAlloc初始化时，将会打开对应的ion驱动设备。
* hardware/qcom/display/msm8998/libgralloc1/gr_ion_alloc.cpp
bool IonAlloc::Init() {
if (ion_dev_fd_ == FD_INIT) {
ion_dev_fd_ = open(kIonDevice, O_RDONLY);
}
if (ion_dev_fd_ < 0) {
ALOGE("%s: Failed to open ion device - %s", __FUNCTION__, strerror(errno));
ion_dev_fd_ = FD_INIT;
return false;
}
return true;
}
heap的类型
ION的驱动在kernel的驱动中，前面说到的system/core中的ion.h其实是自动生成的。我们基于这个开源的分支来看android-msm-wahoo-4.4-oreo-mr1
kernel/drivers/staging/android/ion
Ion定义了6种不同的heap类似，实现不同的分配策略：
* drivers/staging/android/uapi/ion.h
enum ion_heap_type {
ION_HEAP_TYPE_SYSTEM,
ION_HEAP_TYPE_SYSTEM_CONTIG,
ION_HEAP_TYPE_CARVEOUT,
ION_HEAP_TYPE_CHUNK,
ION_HEAP_TYPE_DMA,
ION_HEAP_TYPE_CUSTOM,
ION_NUM_HEAPS = 16,
};
-
ION_HEAP_TYPE_SYSTEM
通过vmallc分配，vmalloc只保证内存在虚拟地址空间是连续的。 -
ION_HEAP_TYPE_SYSTEM_CONTIG
通过kmalloc分配，kmalloc保证物理地址也是连续的。 -
ION_HEAP_TYPE_CARVEOUT
从保留的carveout 中分配一个heap，分配的内存是物理连续的。 -
ION_HEAP_TYPE_CHUNK
分配一快大内存 -
ION_HEAP_TYPE_DMA
通过DMA API分配内存，DMA的Buffer -
ION_HEAP_TYPE_CUSTOM
由用户自己定义，在enum中，必须是最后，这种heap比较特殊
Qcom msm8998中，实现的Ion type如下：
arch/arm/boot/dts/qcom/msm8998-ion.dtsi
&soc {
qcom,ion {
compatible = "qcom,msm-ion";
#address-cells = <1>;
#size-cells = <0>;
system_heap: qcom,ion-heap@25 {
reg = <25>;
qcom,ion-heap-type = "SYSTEM";
};
qcom,ion-heap@22 { /* ADSP HEAP */
reg = <22>;
memory-region = <&adsp_mem>;
qcom,ion-heap-type = "DMA";
};
qcom,ion-heap@27 { /* QSEECOM HEAP */
reg = <27>;
memory-region = <&qseecom_mem>;
qcom,ion-heap-type = "DMA";
};
qcom,ion-heap@13 { /* SPSS HEAP */
reg = <13>;
memory-region = <&sp_mem>;
qcom,ion-heap-type = "DMA";
};
qcom,ion-heap@10 { /* SECURE DISPLAY HEAP */
reg = <10>;
memory-region = <&secure_display_memory>;
qcom,ion-heap-type = "HYP_CMA";
};
qcom,ion-heap@9 {
reg = <9>;
qcom,ion-heap-type = "SYSTEM_SECURE";
};
};
};
Qcom定义了更多的heap类型，做特殊之用。dts中的定义在驱动初始化时，将被读出来，构建ion_platform_heap，用ion_platform_heap进行描述。
* drivers/staging/android/ion/msm/msm_ion.c
static struct ion_platform_data *msm_ion_parse_dt(struct platform_device *pdev)
{
struct ion_platform_data *pdata = 0;
struct ion_platform_heap *heaps = NULL;
struct device_node *node;
struct platform_device *new_dev = NULL;
const struct device_node *dt_node = pdev->dev.of_node;
uint32_t val = 0;
int ret = 0;
uint32_t num_heaps = 0;
int idx = 0;
for_each_available_child_of_node(dt_node, node)
num_heaps++;
if (!num_heaps)
return ERR_PTR(-EINVAL);
pdata = kzalloc(sizeof(struct ion_platform_data), GFP_KERNEL);
if (!pdata)
return ERR_PTR(-ENOMEM);
heaps = kzalloc(sizeof(struct ion_platform_heap)*num_heaps, GFP_KERNEL);
if (!heaps) {
kfree(pdata);
return ERR_PTR(-ENOMEM);
}
pdata->heaps = heaps;
pdata->nr = num_heaps;
for_each_available_child_of_node(dt_node, node) {
new_dev = of_platform_device_create(node, NULL, &pdev->dev);
if (!new_dev) {
pr_err("Failed to create device %s\n", node->name);
goto free_heaps;
}
pdata->heaps[idx].priv = &new_dev->dev;
/**
* TODO: Replace this with of_get_address() when this patch
* gets merged: http://
* permalink.gmane.org/gmane.linux.drivers.devicetree/18614
*/
ret = of_property_read_u32(node, "reg", &val);
if (ret) {
pr_err("%s: Unable to find reg key", __func__);
goto free_heaps;
}
pdata->heaps[idx].id = val;
ret = msm_ion_populate_heap(node, &pdata->heaps[idx]);
if (ret)
goto free_heaps;
msm_ion_get_heap_dt_data(node, &pdata->heaps[idx]);
++idx;
}
return pdata;
free_heaps:
free_pdata(pdata);
return ERR_PTR(ret);
}
ion_platform_heap定定义如下：
* drivers/staging/android/ion/ion.h
/**
* struct ion_platform_heap - defines a heap in the given platform
* @type: type of the heap from ion_heap_type enum
* @id: unique identifier for heap. When allocating higher numbers
* will be allocated from first. At allocation these are passed
* as a bit mask and therefore can not exceed ION_NUM_HEAP_IDS.
* @name: used for debug purposes
* @base: base address of heap in physical memory if applicable
* @size: size of the heap in bytes if applicable
* @has_outer_cache: set to 1 if outer cache is used, 0 otherwise.
* @extra_data: Extra data specific to each heap type
* @priv: heap private data
* @align: required alignment in physical memory if applicable
* @priv: private info passed from the board file
*
* Provided by the board file.
*/
struct ion_platform_heap {
enum ion_heap_type type;
unsigned int id;
const char *name;
ion_phys_addr_t base;
size_t size;
unsigned int has_outer_cache;
void *extra_data;
ion_phys_addr_t align;
void *priv;
};
type，就是dts中的ion-heap-type再加上ION_HEAP_TYPE_的前缀。
id，唯一的，是dts中reg的值
base，是物理地址的起始地址
name 是heap的名字，主要用来debug，以对应的id的形式定义在ion_heap_meta中。
* drivers/staging/android/ion/msm/msm_ion.c
static struct ion_heap_desc ion_heap_meta[] = {
{
.id = ION_SYSTEM_HEAP_ID,
.name = ION_SYSTEM_HEAP_NAME,
},
{
.id = ION_SYSTEM_CONTIG_HEAP_ID,
.name = ION_KMALLOC_HEAP_NAME,
},
{
.id = ION_SECURE_HEAP_ID,
.name = ION_SECURE_HEAP_NAME,
},
{
.id = ION_CP_MM_HEAP_ID,
.name = ION_MM_HEAP_NAME,
.permission_type = IPT_TYPE_MM_CARVEOUT,
},
{
.id = ION_MM_FIRMWARE_HEAP_ID,
.name = ION_MM_FIRMWARE_HEAP_NAME,
},
{
.id = ION_GOOGLE_HEAP_ID,
.name = ION_GOOGLE_HEAP_NAME,
},
{
.id = ION_CP_MFC_HEAP_ID,
.name = ION_MFC_HEAP_NAME,
.permission_type = IPT_TYPE_MFC_SHAREDMEM,
},
{
.id = ION_SF_HEAP_ID,
.name = ION_SF_HEAP_NAME,
},
{
.id = ION_QSECOM_HEAP_ID,
.name = ION_QSECOM_HEAP_NAME,
},
{
.id = ION_SPSS_HEAP_ID,
.name = ION_SPSS_HEAP_NAME,
},
{
.id = ION_AUDIO_HEAP_ID,
.name = ION_AUDIO_HEAP_NAME,
},
{
.id = ION_PIL1_HEAP_ID,
.name = ION_PIL1_HEAP_NAME,
},
{
.id = ION_PIL2_HEAP_ID,
.name = ION_PIL2_HEAP_NAME,
},
{
.id = ION_CP_WB_HEAP_ID,
.name = ION_WB_HEAP_NAME,
},
{
.id = ION_CAMERA_HEAP_ID,
.name = ION_CAMERA_HEAP_NAME,
},
{
.id = ION_ADSP_HEAP_ID,
.name = ION_ADSP_HEAP_NAME,
},
{
.id = ION_SECURE_DISPLAY_HEAP_ID,
.name = ION_SECURE_DISPLAY_HEAP_NAME,
}
};
解析完dts，ion_platform_heap被放在ion_platform_data的heaps中。
创建ion设备，通过ion_device_create函数：
static int msm_ion_probe(struct platform_device *pdev)
{
... ...
new_dev = ion_device_create(compat_msm_ion_ioctl);
创建ion_device成功后，会根据解析出来的ion_platform_heap，通过msm_ion_heap_create创建对应的ion_heap。
msm_ion_allocate 函数如下：
* drivers/staging/android/ion/msm/msm_ion.c
static struct ion_heap *msm_ion_heap_create(struct ion_platform_heap *heap_data)
{
struct ion_heap *heap = NULL;
switch ((int)heap_data->type) {
#ifdef CONFIG_CMA
case ION_HEAP_TYPE_SECURE_DMA:
heap = ion_secure_cma_heap_create(heap_data);
break;
#endif
case ION_HEAP_TYPE_SYSTEM_SECURE:
heap = ion_system_secure_heap_create(heap_data);
break;
case ION_HEAP_TYPE_HYP_CMA:
heap = ion_cma_secure_heap_create(heap_data);
break;
default:
heap = ion_heap_create(heap_data);
}
if (IS_ERR_OR_NULL(heap)) {
pr_err("%s: error creating heap %s type %d base %pa size %zu\n",
__func__, heap_data->name, heap_data->type,
&heap_data->base, heap_data->size);
return ERR_PTR(-EINVAL);
}
heap->name = heap_data->name;
heap->id = heap_data->id;
heap->priv = heap_data->priv;
return heap;
}
实际分配的heap有4种：
|类型|函数实现|
|------|-------|-------|-------|
|ION_HEAP_TYPE_SECURE_DMA|ion_secure_cma_heap_create|ion_cma_secure_heap|ion_secure_cma_ops|
|ION_HEAP_TYPE_SYSTEM_SECURE|ion_system_secure_heap_create|ion_system_secure_heap|system_secure_heap_ops|
|ION_HEAP_TYPE_HYP_CMA|ion_cma_secure_heap_create|ion_heap|ion_secure_cma_ops|
|ION_HEAP_TYPE_SYSTEM default|ion_heap_create|ion_system_heap|system_heap_ops|
创建的ion_heap通过ion_device_add_heap中的plist_add(&heap->node, &dev->heaps)，把每个创建的ion_heap->node链接到ion_device->heaps。
* drivers/staging/android/ion/ion.c
void ion_device_add_heap(struct ion_device *dev, struct ion_heap *heap)
{
struct dentry *debug_file;
if (!heap->ops->allocate || !heap->ops->free || !heap->ops->map_dma ||
!heap->ops->unmap_dma)
pr_err("%s: can not add heap with invalid ops struct.\n",
__func__);
spin_lock_init(&heap->free_lock);
heap->free_list_size = 0;
if (heap->flags & ION_HEAP_FLAG_DEFER_FREE)
ion_heap_init_deferred_free(heap);
if ((heap->flags & ION_HEAP_FLAG_DEFER_FREE) || heap->ops->shrink)
ion_heap_init_shrinker(heap);
heap->dev = dev;
down_write(&dev->lock);
/*
* use negative heap->id to reverse the priority -- when traversing
* the list later attempt higher id numbers first
*/
plist_node_init(&heap->node, -heap->id);
plist_add(&heap->node, &dev->heaps);
debug_file = debugfs_create_file(heap->name, 0664,
dev->heaps_debug_root, heap,
&debug_heap_fops);
... ...
up_write(&dev->lock);
}
- ION_HEAP_TYPE_SECURE_DMA
SECURE_DMA类型相关的实现如下：
* drivers/staging/android/ion/ion_cma_secure_heap.c
struct ion_cma_secure_heap {
struct device *dev;
/*
* Protects against races between threads allocating memory/adding to
* pool at the same time. (e.g. thread 1 adds to pool, thread 2
* allocates thread 1's memory before thread 1 knows it needs to
* allocate more.
* Admittedly this is fairly coarse grained right now but the chance for
* contention on this lock is unlikely right now. This can be changed if
* this ever changes in the future
*/
struct mutex alloc_lock;
/*
* protects the list of memory chunks in this pool
*/
struct mutex chunk_lock;
struct ion_heap heap;
/*
* Bitmap for allocation. This contains the aggregate of all chunks. */
unsigned long *bitmap;
/*
* List of all allocated chunks
*
* This is where things get 'clever'. Individual allocations from
* dma_alloc_coherent must be allocated and freed in one chunk.
* We don't just want to limit the allocations to those confined
* within a single chunk (if clients allocate n small chunks we would
* never be able to use the combined size). The bitmap allocator is
* used to find the contiguous region and the parts of the chunks are
* marked off as used. The chunks won't be freed in the shrinker until
* the usage is actually zero.
*/
struct list_head chunks;
int npages;
ion_phys_addr_t base;
struct work_struct work;
unsigned long last_alloc;
struct shrinker shrinker;
atomic_t total_allocated;
atomic_t total_pool_size;
atomic_t total_leaked;
unsigned long heap_size;
unsigned long default_prefetch_size;
};
ion_cma_secure_heap继承ion_heap，又扩展了很多实现
SECURE_DMA对应的Ops如下：
static struct ion_heap_ops ion_secure_cma_ops = {
.allocate = ion_secure_cma_allocate,
.free = ion_secure_cma_free,
.map_dma = ion_secure_cma_heap_map_dma,
.unmap_dma = ion_secure_cma_heap_unmap_dma,
.phys = ion_secure_cma_phys,
.map_user = ion_secure_cma_mmap,
.map_kernel = ion_secure_cma_map_kernel,
.unmap_kernel = ion_secure_cma_unmap_kernel,
.print_debug = ion_secure_cma_print_debug,
};
Ops就是ioctl下来的，相关cmd的实现。
- ION_HEAP_TYPE_SYSTEM_SECURE
SYSTEM_SECURE采用ion_system_secure_heap进行 描述，继承ion_heap。
* drivers/staging/android/ion/ion_system_secure_heap.c
struct ion_system_secure_heap {
struct ion_heap *sys_heap;
struct ion_heap heap;
/* Protects prefetch_list */
spinlock_t work_lock;
bool destroy_heap;
struct list_head prefetch_list;
struct delayed_work prefetch_work;
};
对应的接口实现为system_secure_heap_ops
static struct ion_heap_ops system_secure_heap_ops = {
.allocate = ion_system_secure_heap_allocate,
.free = ion_system_secure_heap_free,
.map_dma = ion_system_secure_heap_map_dma,
.unmap_dma = ion_system_secure_heap_unmap_dma,
.map_kernel = ion_system_secure_heap_map_kernel,
.unmap_kernel = ion_system_secure_heap_unmap_kernel,
.map_user = ion_system_secure_heap_map_user,
.shrink = ion_system_secure_heap_shrink,
};
- ION_HEAP_TYPE_HYP_CMA
HYP_CMA主要用于Secure 显示。HYP_CMA没有做扩展，还是用ion_heap描述。但是采用Ops为ion_secure_cma_ops。
* drivers/staging/android/ion/ion_cma_heap.c
static struct ion_heap_ops ion_secure_cma_ops = {
.allocate = ion_secure_cma_allocate,
.free = ion_secure_cma_free,
.map_dma = ion_cma_heap_map_dma,
.unmap_dma = ion_cma_heap_unmap_dma,
.phys = ion_cma_phys,
.map_user = ion_cma_mmap,
.map_kernel = ion_cma_map_kernel,
.unmap_kernel = ion_cma_unmap_kernel,
.print_debug = ion_cma_print_debug,
};
- 除上面3中类型外，其他的类型，通过ion_heap_create分配
具体的对应关系如下：
* drivers/staging/android/ion/ion_heap.c
struct ion_heap *ion_heap_create(struct ion_platform_heap *heap_data)
{
struct ion_heap *heap = NULL;
switch (heap_data->type) {
case ION_HEAP_TYPE_SYSTEM_CONTIG:
pr_err("%s: Heap type is disabled: %d\n", __func__,
heap_data->type);
return ERR_PTR(-EINVAL);
case ION_HEAP_TYPE_SYSTEM:
heap = ion_system_heap_create(heap_data);
break;
case ION_HEAP_TYPE_CARVEOUT:
heap = ion_carveout_heap_create(heap_data);
break;
case ION_HEAP_TYPE_CHUNK:
heap = ion_chunk_heap_create(heap_data);
break;
case ION_HEAP_TYPE_DMA:
heap = ion_cma_heap_create(heap_data);
break;
default:
pr_err("%s: Invalid heap type %d\n", __func__,
heap_data->type);
return ERR_PTR(-EINVAL);
}
if (IS_ERR_OR_NULL(heap)) {
pr_err("%s: error creating heap %s type %d base %pa size %zu\n",
__func__, heap_data->name, heap_data->type,
&heap_data->base, heap_data->size);
return ERR_PTR(-EINVAL);
}
heap->name = heap_data->name;
heap->id = heap_data->id;
heap->priv = heap_data->priv;
return heap;
}
比如，ion_system_heap_create类型,采用ion_system_heap描述，继承ion_heap.
* drivers/staging/android/ion/ion_system_heap.c
struct ion_system_heap {
struct ion_heap heap;
struct ion_page_pool **uncached_pools;
struct ion_page_pool **cached_pools;
struct ion_page_pool **secure_pools[VMID_LAST];
/* Prevents unnecessary page splitting */
struct mutex split_page_mutex;
};
对应的Ops为system_heap_ops：
static struct ion_heap_ops system_heap_ops = {
.allocate = ion_system_heap_allocate,
.free = ion_system_heap_free,
.map_dma = ion_system_heap_map_dma,
.unmap_dma = ion_system_heap_unmap_dma,
.map_kernel = ion_heap_map_kernel,
.unmap_kernel = ion_heap_unmap_kernel,
.map_user = ion_heap_map_user,
.shrink = ion_system_heap_shrink,
};
Ion API
在用户空间，提供了系统调用ioctl，对应内存空间的API，内核空间的API对应具体类型的Heap的API。Heap的API用ion_heap_ops描述，前面我们已经说过了每种类型的API对应的ion_heap_ops。
除了Ion的标准API外，Qcom又定制了一些自己的ioctl，定制的ioctl实现为compat_msm_ion_ioctl，在下面的代码中
* drivers/staging/android/ion/compat_msm_ion.c
Ion标准的ioctl，在ion_ioctl中：
* drivers/staging/android/ion/ion.c
static const struct file_operations ion_fops = {
.owner = THIS_MODULE,
.open = ion_open,
.release = ion_release,
.unlocked_ioctl = ion_ioctl,
.compat_ioctl = compat_ion_ioctl,
};
在我们的测试代码中，Producer设置是usage为GRALLOC_USAGE_SW_WRITE_OFTEN，Consumer中设置的usage为USAGE_HW_COMPOSER，Layer创建的时候设置的。
uint32_t Layer::getEffectiveUsage(uint32_t usage) const {
// TODO: should we do something special if mSecure is set?
if (mProtectedByApp) {
// need a hardware-protected path to external video sink
usage |= GraphicBuffer::USAGE_PROTECTED;
}
if (mPotentialCursor) {
usage |= GraphicBuffer::USAGE_CURSOR;
}
usage |= GraphicBuffer::USAGE_HW_COMPOSER;
return usage;
}
GRALLOC_USAGE_SW_WRITE_OFTEN将被转换为 GRALLOC1_PRODUCER_USAGE_CPU_WRITE_OFTEN；USAGE_HW_COMPOSER将被转换为GRALLOC1_CONSUMER_USAGE_HWCOMPOSER；对应的heap id为ION_SYSTEM_HEAP_ID。
下面，以ION_HEAP_TYPE_SYSTEM为例，我们通过一个表格来描述他们直接的关系，和API的用途
| 用户空间API | 内核空间API | Heap API | 作用 | ||
|---|---|---|---|---|---|
| open | ion_client_create | null | 分配一个Ion的客户端，客户端负责和Ion设备进行通信 | ||
| close | ion_client_destroy | null | 释放一个Ion的客户端 | ||
| ION_IOC_ALLOC | ion_buffer_create | ion_system_heap_allocate，map_dma | 申请一块Ion内存，返回Ion Handle | ||
| ION_IOC_FREE | ion_free ion_free_nolock | ion_system_heap_free | 释放Ion handle | ||
| ION_IOC_SHARE & ION_IOC_MAP | ion_share_dma_buf_fd | null | 为制定的Buffer创建DMA映射，返回DMA Buffer的FD | ||
| ION_IOC_IMPORT | ion_import_dma_buf | null | 通过DMA的FD，返回Ion Buffer的Handle | ION_IOC_CUSTOM | |
| mmap | ion_mmap | ion_heap_map_user | map内存到user空间 |
Qcom定制的Ioctl，ION_IOC_CUSTOM还有
ION_IOC_CLEAN_CACHES
ION_IOC_INV_CACHES
ION_IOC_CLEAN_INV_CACHES
ION_IOC_PREFETCH
ION_IOC_DRAIN
ION是通过handle而非buffer地址来实现驱动间共享内存，用户空间共享内存也是利用同样原理，所以，map，import都是通过handle来完成。另外，Ion Buffer创建后，映射到 DMA Buffer，后续通过DMA Buffer来处理。
我们我们来看他们之间的关系类图～
ION 关系类图
Ion Debug
Ion 在/sys/kernel/debug/ion/ 提供一个debugfs 接口。
... /sys/kernel/debug/ion # ls
clients egl heaps
每个heap都有自己的debugfs目录，client内存使用状况显示在/sys/kernel/debug/ion/heaps/<<heap name>>
... /sys/kernel/debug/ion/heaps # ls
carveout_fb carveout_fb_shrink carveout_overlay carveout_overlay_shrink system system_shrink
比如这个system的分配情况：
... /sys/kernel/debug/ion/heaps # cat system
client pid size
----------------------------------------------------
----------------------------------------------------
orphaned allocations (info is from last known client):
client pid user user_pid size mcnt rcnt
allocator@2.0-s 257 composer@2.1-se 258 7372800 0 1
allocator@2.0-s 257 composer@2.1-se 258 139264 0 1
allocator@2.0-s 257 composer@2.1-se 258 139264 0 1
allocator@2.0-s 257 composer@2.1-se 258 3686400 0 1
allocator@2.0-s 257 composer@2.1-se 258 3686400 0 1
allocator@2.0-s 257 composer@2.1-se 258 3686400 0 1
allocator@2.0-s 257 composer@2.1-se 258 139264 0 1
----------------------------------------------------
total orphaned 18849792
total 18849792
deferred free 0
----------------------------------------------------
4 order 8 highmem pages in uncached pool = 4194304 total
2 order 8 lowmem pages in uncached pool = 2097152 total
14 order 4 highmem pages in uncached pool = 917504 total
0 order 4 lowmem pages in uncached pool = 0 total
0 order 0 highmem pages in uncached pool = 0 total
838 order 0 lowmem pages in uncached pool = 3432448 total
0 order 8 highmem pages in cached pool = 0 total
0 order 8 lowmem pages in cached pool = 0 total
0 order 4 highmem pages in cached pool = 0 total
0 order 4 lowmem pages in cached pool = 0 total
0 order 0 highmem pages in cached pool = 0 total
0 order 0 lowmem pages in cached pool = 0 total
前面是ion Client的pid，这里的allocator@2.0-service。然后是使用者pid，这里是composer@2.1-service（大部分Buffer都是这个进分配的，用于显示）。
小结
本章主要讲述GraphicBuffer相关的流程，结合 Qcom的msm8998，讲述了Gralloc1.0的接口实现，介绍了Ion使用及Ion驱动实现。
