linux驱动-使用sysfs_create_group创建sy

1、创建属性文件的sysfs接口：

1.1 创建属性文件的sysfs接口函数
ret = sysfs_create_group(&pdev->dev.kobj,&gpio_attr_grp);
sysfs_create_group()在kobj目录下创建一个属性集合，并显示集合中的属性文件。如果文件已存在，会报错。

1.2 删除接口函数
sysfs_remove_group(&pdev->dev.kobj,&gpio_keys_attr_group);
sysfs_remove_group()在kobj目录下删除一个属性集合，并删除集合中的属性文件

2、测试实例代码

2.1 驱动c代码

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#include <linux/extcon.h>
#include <linux/gpio.h>
#include <linux/of_gpio.h>
#include <linux/irq.h>
#include <linux/interrupt.h>
#include <linux/delay.h>
 
static ssize_t vpd_flip_show(struct device *dev,
                 struct device_attribute *attr, char *buf)
{
 
    return sprintf(buf, "%d\n", 855);
}
 
static ssize_t vpd_flip_store(struct device *dev,
                  struct device_attribute *attr,
                  const char *buf, size_t count)
{
     dev_info(dev, "%s: %d enter string:%s\n", __func__, __LINE__,buf);
    return count;
}
static DEVICE_ATTR(flip, S_IWUSR | S_IRUSR, vpd_flip_show, vpd_flip_store);
 
static ssize_t vpd_ss_show(struct device *dev,
               struct device_attribute *attr, char *buf)
{
 
    return sprintf(buf, "%d\n", 350);
}
 
static ssize_t vpd_ss_store(struct device *dev,
                  struct device_attribute *attr,
                  const char *buf, size_t count)
{
    dev_info(dev, "%s: %d enter string:%s\n", __func__, __LINE__,buf);
    return count;
}
static DEVICE_ATTR(ss, S_IWUSR | S_IRUSR, vpd_ss_show, vpd_ss_store);
static ssize_t vpd_mode_show(struct device *dev,
               struct device_attribute *attr, char *buf)
{
    dev_info(dev, "%s: %d enter string:%s\n", __func__, __LINE__,buf);
    return sprintf(buf, "%d\n", 120);
}
 
static ssize_t vpd_mode_store(struct device *dev,
                  struct device_attribute *attr,
                  const char *buf, size_t count)
{
    dev_info(dev, "%s: %d enter string:%s\n", __func__, __LINE__,buf);
    return count;
}
static DEVICE_ATTR(mode, S_IWUSR | S_IRUSR, vpd_mode_show, vpd_mode_store);
 
static ssize_t vpd_enable_show(struct device *dev,
                 struct device_attribute *attr, char *buf)
{
    return sprintf(buf, "%d\n", 520);
}
static ssize_t vpd_enable_store(struct device *dev,
                  struct device_attribute *attr,
                  const char *buf, size_t count)
{
    dev_info(dev, "%s: %d enter string:%s\n", __func__, __LINE__,buf);
    return count;
}
static DEVICE_ATTR(enable, S_IWUSR | S_IRUSR, vpd_enable_show, vpd_enable_store);
 
static struct attribute *vpd_attributes[] = {
    &dev_attr_flip.attr,
    &dev_attr_ss.attr,
    &dev_attr_mode.attr,
    &dev_attr_enable.attr,
    NULL////属性结构体数组最后一项必须以NULL结尾。
};static const struct attribute_group vpd_attr_group = {
    .attrs = vpd_attributes,
};
 
static int vpd_extcon_probe(struct platform_device *pdev)
{
    struct virtual_pd *vpd;
    struct device *dev = &pdev->dev;
    int ret = 0;
    dev_info(dev, "%s: %d d29dstart\n", __func__, __LINE__);
 
    ret = sysfs_create_group(&dev->kobj, &vpd_attr_group);
    if (ret < 0)
        dev_warn(dev, "attr group create failed\n");
    else
        dev_info(dev, "attr group create success!\n");
 
    
    dev_info(dev, "%s: %d sussess\n", __func__, __LINE__);
 
    return 0;
}
static int vpd_extcon_remove(struct platform_device *pdev)
{
    dev_info("8", "%s: %d \n", __func__, __LINE__);
    return 0;
}
 
 
 
static const struct of_device_id vpd_extcon_dt_match[] = {
    { .compatible = "linux,sysfs_create_group_test", },
    { /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, vpd_extcon_dt_match);
static struct platform_driver vpd_extcon_driver = {
    .probe      = vpd_extcon_probe,
    .remove     = vpd_extcon_remove,
    .driver     = {
        .name   = "sysfs_create_group_test",
        .of_match_table = vpd_extcon_dt_match,
    },
};
static int __init __vpd_extcon_init(void)
{
        return platform_driver_register(&vpd_extcon_driver);
}
 
static void __exit __vpd_extcon_exit(void)
{
        platform_driver_unregister(&vpd_extcon_driver);
}
 
module_init(__vpd_extcon_init);
module_exit(__vpd_extcon_exit);
 
MODULE_LICENSE("GPL");
MODULE_AUTHOR("tanghanyue");
MODULE_DESCRIPTION("Virtual Typec-pd extcon driver")

2.2 dts文件添加下面内容

test-power {

status = "okay";

compatible = "linux,sysfs_create_group_test";

};

3、执行测试

3.1 adb控制台，可以看到/sys/devices/platform/文件夹下面生产sysfs_create文件夹，该文件夹下面有mode等节点。

图片.png

3.2执行结果，串口打印信息

图片.png

备注:
msm-4.14/drivers/hid/hid-qvr.c

qvr_external_sensor_init--->sysfs_create_group(qvr_external_sensor_kobj, &attr_group); 创建sys 接口

qvr_external_sensor_kobj = kobject_create_and_add("qvr_external_sensor", kernel_kobj);
static struct attribute_group attr_group = {
    .attrs = attrs,
};

static struct attribute *attrs[] = {
    &fd_attribute.attr,
    &ts_base_attribute.attr,
    &ts_offset_attribute.attr,
    NULL,
};


static struct kobj_attribute fd_attribute = __ATTR(fd, 0664,
    fd_show,
    fd_store);



static ssize_t fd_store(struct kobject *kobj,
    struct kobj_attribute *attr,
    const char *buf, size_t count)
{
    struct qvr_external_sensor *sensor = &qvr_external_sensor;
    int ret;

    ret = kstrtoint(buf, 10, &sensor->fd);
    if (ret < 0)
        return ret;
    if (sensor->fd == -1)
        kernel_unmap_gyro_buffer();
    else
        kernel_map_gyro_buffer();----->进行了sensor->vaddr = dma_buf_kmap(sensor->qvr_buf, 0);  不在释放
    sensor->ts_base = 0;
    sensor->ts_offset = 0;

    return count;
}


static int kernel_map_gyro_buffer(void)
{
    struct qvr_external_sensor *sensor = &qvr_external_sensor;
    int ret = 0;

    sensor->qvr_buf = dma_buf_get(sensor->fd);
    if (IS_ERR_OR_NULL(sensor->qvr_buf)) {
        ret = -ENOMEM;
        pr_err("dma_buf_get failed for fd: %d\n", sensor->fd);
        goto done;
    }
    ret = dma_buf_begin_cpu_access(sensor->qvr_buf, DMA_BIDIRECTIONAL);
    if (ret) {
        pr_err("%s: dma_buf_begin_cpu_access failed\n", __func__);
        goto err_dma;
    }
    sensor->vsize = sensor->qvr_buf->size;
    sensor->vaddr = dma_buf_kmap(sensor->qvr_buf, 0);
    if (IS_ERR_OR_NULL(sensor->vaddr)) {
        ret = -ENOMEM;
        pr_err("dma_buf_kmap failed for fd: %d\n", sensor->fd);
        goto err_end_access;
    }

    return 0;

err_end_access:
    dma_buf_end_cpu_access(sensor->qvr_buf, DMA_BIDIRECTIONAL);
err_dma:
    dma_buf_put(sensor->qvr_buf);
    sensor->qvr_buf = NULL;
done:
    return ret;

}