玩转移远SC60 Android开发板------（4）USB和otg切换

在SC60上打算实现usb device和otg的软切换，即通过软件设置实现usb device和otg的切换。
原理图上可以设计一个GPIO来控制USB ID和数据线的切换。VBUS的供电方面，otg使用外供电，可以不用考虑；作device时vbus用来检测插入即可。
参考原理图如下：

图中使用GPIO_96作为控制切换的管脚，它输出0时，USB_ID脚为高，s脚为高，usb切换开关选择的是HSD1：USB_DP_EXT和USB_DM_EXT，此时模块作为device；
GPIO_96输出1时，USB_ID脚为低，usb切换开关选择的是HSD2：USB_DP_COM和USB_DM_COM，此时模块作为host，外部连接otg设备。

参考驱动：

#include <linux/device.h>
#include <asm/io.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/uaccess.h>
#include <linux/slab.h>
#include <linux/cdev.h>
#include <linux/types.h>
#include <linux/fs.h>
#include <linux/module.h>
#include <linux/semaphore.h>
#include <linux/of_device.h>
#include <linux/of_platform.h>
#include <linux/sched.h>
#include <linux/kthread.h>
#include <linux/delay.h>
#include <linux/gpio.h>#define SC60_GPIO_SET_MAJOR    198
#define SC60_DO1            0x1
#define SC60_DO2            0x2u32 gpio_num[]={96,
};struct SC60_gpio_dev{struct cdev cdev;
};struct SC60_gpio_dev *SC60_gpio_devp;static int SC60_gpio_major = SC60_GPIO_SET_MAJOR;int SC60_gpio_open(struct inode *inode, struct file *filp)
{//printk(KERN_ERR "###sc60### SC60_gpio open in\n");filp->private_data = SC60_gpio_devp;return 0;
}int SC60_gpio_release(struct inode *inode, struct file *filp)
{//printk(KERN_ERR "###sc60### SC60_gpio release in\n");return 0;
}static ssize_t SC60_gpio_read(struct file *filp, char __user *buf, size_t size, loff_t *ppos)
{__attribute__((__unused__)) struct SC60_gpio_dev *dev = filp->private_data;//copy_to_user//printk(KERN_ERR "###sc60### SC60_gpio read in\n");return 0;
}static ssize_t SC60_gpio_write(struct file *filp, const char __user *buf, size_t size, loff_t *ppos)
{__attribute__((__unused__)) struct SC60_gpio_dev *dev = filp->private_data;//copy_from_user//printk(KERN_ERR "###sc60### SC60_gpio write in\n");return -1;
}static loff_t SC60_gpio_llseek(struct file *filp, loff_t offset, int orig)
{//printk(KERN_ERR "###sc60### SC60_gpio llseek in\n");//filp->f_posswitch(orig){case 0:break;case 1:break;default:break;}return 0;
}static long SC60_gpio_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{__attribute__((__unused__)) struct SC60_gpio_dev *dev = filp->private_data;//printk(KERN_ERR "###sc60### SC60_gpio ioctl in\n");switch(cmd){case SC60_DO1:break;case SC60_DO2:default:break;}return 0;
}static const struct file_operations SC60_gpio_fops = {.owner = THIS_MODULE,.llseek = SC60_gpio_llseek,.read = SC60_gpio_read,.write = SC60_gpio_write,.unlocked_ioctl = SC60_gpio_ioctl,.open = SC60_gpio_open,.release = SC60_gpio_release,
};struct class *SC60_gpio_class;static void SC60_gpio_setup_cdev(struct SC60_gpio_dev *dev, int index)
{int err, devno;devno = MKDEV(SC60_gpio_major, index);printk(KERN_ERR "###sc60### SC60_gpio SC60_gpio_setup_cdev\n");cdev_init(&dev->cdev, &SC60_gpio_fops);dev->cdev.owner = THIS_MODULE;err = cdev_add(&dev->cdev, devno, 1);if(err){printk(KERN_ERR "###sc60### %d add SC60_gpio %d\n", err, index);}SC60_gpio_class = class_create(THIS_MODULE, "sc60_otg_set");//stone comment//这里的名字是/dev/下面的名字// create device in /dev/sc60_otg_set//实际在/sys/class/sc60_otg_set// but the real device is /sys/bus/platform/devices/SC60_otg_controldevice_create(SC60_gpio_class, NULL, devno, NULL, "sc60_otg_set");
}static bool gpio_flag = 0;static ssize_t SC60_gpio_get(struct device *dev, struct device_attribute *attr, char *buf)
{int ret = 0;if(gpio_flag)//print chars to buf//ret = snprintf(buf, PAGE_SIZE, "%d\n", SC60_adc1_to_vol());ret = snprintf(buf, PAGE_SIZE, "--otg set--\n");elseret = snprintf(buf, PAGE_SIZE, "--host set--\n");return ret;
}static ssize_t SC60_gpio_set(struct device *dev, struct device_attribute *attr, const char *buf, size_t count)
{int stat;//char to intstat = buf[0] - '0';printk(KERN_ERR "set gpio status :%d \n", stat);gpio_free(gpio_num[0]);gpio_request(gpio_num[0], NULL);if(stat == 0){gpio_direction_output(gpio_num[0], 0);gpio_flag = stat;}if(stat == 1){gpio_direction_output(gpio_num[0], 1);gpio_flag = stat;}return count;
}
static DEVICE_ATTR(SC60_gpio, 0664, SC60_gpio_get, SC60_gpio_set);static int __init SC60_gpio_probe(struct platform_device *pdev)
{int result;dev_t devno = MKDEV(SC60_gpio_major, 0);printk(KERN_ERR "###sc60### SC60_gpio_probe in\n");if(SC60_gpio_major){//这里是分配设备号//cat proc/devices 看到198 SC60_gpio_controlresult = register_chrdev_region(devno, 1, "SC60_gpio_control");}else{result = alloc_chrdev_region(&devno, 0, 1, "SC60_gpio_control");SC60_gpio_major = MAJOR(devno);}if(result < 0){return result;}SC60_gpio_devp = kmalloc(sizeof(struct SC60_gpio_dev), GFP_KERNEL);if(!SC60_gpio_devp){result = -ENOMEM;goto fail_malloc;}memset(SC60_gpio_devp, 0, sizeof(struct SC60_gpio_dev));SC60_gpio_setup_cdev(SC60_gpio_devp, 0);//这里创建的节点是在/sys/bus/platform/devices/SC60_otg_control下//SC60_otg_control这个名字是由SC60_gpio_device和SC60_gpio_device_driver的名字决定的device_create_file(&pdev->dev, &dev_attr_sc60_gpio);printk(KERN_ERR "###sc60### SC60_gpio_probe out\n");return 0;fail_malloc:unregister_chrdev_region(devno, 1);return result;
}static int __exit SC60_gpio_remove(struct platform_device *pdev)
{cdev_del(&SC60_gpio_devp->cdev);kfree(SC60_gpio_devp);device_destroy(SC60_gpio_class, MKDEV(SC60_gpio_major, 0));class_destroy(SC60_gpio_class);unregister_chrdev_region(MKDEV(SC60_gpio_major, 0), 1);return 0;
}static struct platform_driver SC60_gpio_device_driver = {.probe   = SC60_gpio_probe,.remove  = SC60_gpio_remove,.driver  = {.name = "SC60_otg_control",.owner = THIS_MODULE,},
};static struct platform_device SC60_gpio_device = {.name    = "SC60_otg_control",.id      = -1,
};static int __init SC60_gpio_init(void)
{platform_device_register(&SC60_gpio_device);return platform_driver_register(&SC60_gpio_device_driver);
}static void __exit SC60_codec_exit(void)
{platform_driver_unregister(&SC60_gpio_device_driver);platform_device_unregister(&SC60_gpio_device);
}module_init(SC60_gpio_init);
module_exit(SC60_codec_exit);MODULE_LICENSE("GPL");
MODULE_AUTHOR("stone");
MODULE_DESCRIPTION("stone for SC60 gpio-set CTRL");

这样就可以使用节点控制usb状态了。
读取otg状态：
cat /sys/bus/platform/devices/sc60_otg_control/sc60_gpio
设置otg状态：
echo 1 > /sys/bus/platform/devices/sc60_otg_control/sc60_gpio
设置USB状态：
echo 0 > /sys/bus/platform/devices/sc60_otg_control/sc60_gpio

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