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;
}
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