UVC系列4-定制Android kernel UVC部分支持相

2019-04-28 本文已影响0人 cg1991

在熟悉了android uvc控制参数和UVC协议之后，现在可以着手定制android UVC协议了，添加相对控制参数。

第一步，添加相对控制pan和tilt修改的文件是：drivers\media\usb\uvc\uvc_ctrl.c
在uvc_control_info uvc_ctrls[]结构体中添加：

{
    .entity               = UVC_GUID_UVC_CAMERA,
    .selector  = UVC_CT_PANTILT_RELATIVE_CONTROL,
    .index               = 12,
    .size          = 4,
    .flags     = UVC_CTRL_FLAG_SET_CUR
                 |UVC_CTRL_FLAG_GET_RANGE
                 |UVC_CTRL_FLAG_AUTO_UPDATE,
}

在结构体uvc_control_mapping uvc_ctrl_mappings[]中添加：

{
    .id = V4L2_CID_PAN_RELATIVE,
    .name = "Pan (Relative)",
    .entity = UVC_GUID_UVC_CAMERA,
    .selector = UVC_CT_PANTILT_RELATIVE_CONTROL,
    .size = 16,
    .offset = 0,
    .v4l2_type = V4L2_CTRL_TYPE_INTEGER,
    .data_type = UVC_CTRL_DATA_TYPE_SIGNED,
    .get = uvc_ctrl_get_rel_speed,
    .set = uvc_ctrl_set_rel_speed,
},
{
    .id = V4L2_CID_TILT_RELATIVE,
    .name= "Tilt (Relative)",
    .entity= UVC_GUID_UVC_CAMERA,
    .selector= UVC_CT_PANTILT_RELATIVE_CONTROL,
    .size= 16,
    .offset= 16,
    .v4l2_type= V4L2_CTRL_TYPE_INTEGER,
    .data_type= UVC_CTRL_DATA_TYPE_SIGNED,
    .get= uvc_ctrl_get_rel_speed,
    .set= uvc_ctrl_set_rel_speed,
}

其中uvc_ctrl_get_rel_speed和uvc_ctrl_set_rel_speed映射到的方法对应UVC协议里面的速度控制，在uvc_ctrl.c文件中也要添加这两个方法的实现，与zoom对应的控制方法类似，具体实现方法是：

static __s32 uvc_ctrl_get_rel_speed(structuvc_control_mapping *mapping,__u8query, const __u8 *data)
{
    intfirst = mapping->offset / 8;
    __s8rel = (__s8)data[first];
    switch (query) {
    case UVC_GET_CUR:
        return (rel == 0) ? 0 : (rel > 0 ?data[first+1]:-data[first+1]);
    case UVC_GET_MIN:
        return -data[first+1];
    case UVC_GET_MAX:
    case UVC_GET_RES:
    case UVC_GET_DEF:
    default:
        return data[first+1];
}
}
static void uvc_ctrl_set_rel_speed(structuvc_control_mapping *mapping,__s32 value, __u8 *data)
{
    intfirst = mapping->offset / 8;
    data[first] = value == 0 ? 0 : (value > 0)? 1 : 0xff;
    data[first+1] = min_t(int, abs(value), 0xff);
}

可以看到这里的赋值也是与UVC协议对应的。另外针对绝对控制，目前在结构体uvc_control_mappinguvc_ctrl_mappings[]中的定义是：

{
    .id             = V4L2_CID_PAN_ABSOLUTE,
    .name               = "Pan (Absolute)",
    .entity               = UVC_GUID_UVC_CAMERA,
    .selector  = UVC_CT_PANTILT_ABSOLUTE_CONTROL,
    .size          = 32,
    .offset              = 0,
    .v4l2_type        = V4L2_CTRL_TYPE_INTEGER,
    .data_type       = UVC_CTRL_DATA_TYPE_UNSIGNED,
},
{
    .id             = V4L2_CID_TILT_ABSOLUTE,
    .name               = "Tilt (Absolute)",
    .entity               = UVC_GUID_UVC_CAMERA,
    .selector  = UVC_CT_PANTILT_ABSOLUTE_CONTROL,
    .size          = 32,
    .offset              = 32,
    .v4l2_type        = V4L2_CTRL_TYPE_INTEGER,
    .data_type       = UVC_CTRL_DATA_TYPE_UNSIGNED,
}

可以看看这两个控制参数的data_type是UVC_CTRL_DATA_TYPE_UNSIGNED，而UVC协议里面定义的是：

image
Value的类型是signed number，此时我们需要将UNSIGNED改为signed，将这个data_type统一改成signed，即UVC_CTRL_DATA_TYPE_SIGNED。
下一步uvc_control_mapping uvc_ctrl_mappings[]中添加速度控制的参数，如下：

{
    .id             = V4L2_CID_PAN_SPEED,
    .name               = "Pan (Speed)",
    .entity               = UVC_GUID_UVC_CAMERA,
    .selector  = UVC_CT_PANTILT_RELATIVE_CONTROL,
    .size          = 16,
    .offset              = 0,
    .v4l2_type        = V4L2_CTRL_TYPE_INTEGER,
    .data_type       = UVC_CTRL_DATA_TYPE_SIGNED,
    .get          = uvc_ctrl_get_rel_speed,
    .set           = uvc_ctrl_set_rel_speed,
},
{
    .id             = V4L2_CID_TILT_SPEED,
    .name               = "Tilt (Speed)",
    .entity               = UVC_GUID_UVC_CAMERA,
    .selector  = UVC_CT_PANTILT_RELATIVE_CONTROL,
    .size          =16,
    .offset              = 16,
    .v4l2_type        = V4L2_CTRL_TYPE_INTEGER,
    .data_type       = UVC_CTRL_DATA_TYPE_SIGNED,
    .get          = uvc_ctrl_get_rel_speed,
    .set           = uvc_ctrl_set_rel_speed,
}

针对相对控制的两个参数id V4L2_CID_PAN_RELATIVE和V4L2_CID_PAN_RELATIVE，两个控制速度的参数V4L2_CID_PAN_SPEED和V4L2_CID_TILT_SPEED需要定义，修改两个文件，第一个文件位置位于drivers\media\v4l2-core\v4l2-ctrls.c文件中，const char *v4l2_ctrl_get_name中添加：

caseV4L2_CID_PAN_RELATIVE:      return"Pan, Relative";
caseV4L2_CID_TILT_RELATIVE:     return"Tilt, Relative";
caseV4L2_CID_PAN_SPEED:         return"Pan, Speed";
caseV4L2_CID_TILT_SPEED:        return"Tilt, Speed";

第二个文件位于include/uapi/linux/v4l2-controls.h，添加定义：

#define V4L2_CID_PAN_RELATIVE                   (V4L2_CID_CAMERA_CLASS_BASE+4)
#define V4L2_CID_TILT_RELATIVE                  (V4L2_CID_CAMERA_CLASS_BASE+5)
#define V4L2_CID_PAN_SPEED                      (V4L2_CID_CAMERA_CLASS_BASE+32)
#define V4L2_CID_TILT_SPEED                     (V4L2_CID_CAMERA_CLASS_BASE+33)

另外还有两个xml说明文件，需要添加这两个控制的说明，分别是：

Documentation/DocBook/media/v4l/controls.xml
Documentation/DocBook/media/v4l/compat.xml
具体修改网址可以参考：
https://patchwork.kernel.org/patch/4836491/

至此，android UVC kernel部分定制完毕，下一步就是打通app到底层kernel的通道,将这些代码合入完毕之后，开始编译kernel代码，并刷机重启。
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UVC系列4-定制Android kernel UVC部分支持相

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