Linux usb驱动程序全注释
/*
* USB Skeleton driver - 2.0
*/
#include <linux/config.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/kref.h>
#include <linux/smp_lock.h>
#include <linux/usb.h>
#include <asm/uaccess.h>
/* Define these values to match your devices */
#define USB_SKEL_VENDOR_ID 0xfff0//定义厂商ID
#define USB_SKEL_PRODUCT_ID 0xfff0//定义产品ID
/* 描述驱动支持的USB设备结构 */
static struct usb_device_id skel_table [] = {
{ USB_DEVICE(USB_SKEL_VENDOR_ID, USB_SKEL_PRODUCT_ID) },
{ } /* Terminating entry */
};
MODULE_DEVICE_TABLE (usb, skel_table);
/* Get a minor range for your devices from the usb maintainer */
#define USB_SKEL_MINOR_BASE 192
/* 定义一个结构包含所有我们所需要的设备成员 */
struct usb_skel {
struct usb_device * udev; /* the usb device for this device */
struct usb_interface * interface; /* the interface for this device */
unsigned char * bulk_in_buffer; /* the buffer to receive data */
size_t bulk_in_size; /* the size of the receive buffer */
__u8 bulk_in_endpointAddr; /* the address of the bulk in endpoint */
__u8 bulk_out_endpointAddr; /* the address of the bulk out endpoint */
struct kref kref;/*内核引用计数*/
};
#define to_skel_dev(d) container_of(d, struct usb_skel, kref)
static struct usb_driver skel_driver;//定义一个usb设备驱动
static void skel_delete(struct kref *kref)
{
struct usb_skel *dev = to_skel_dev(kref);
usb_put_dev(dev->udev);
kfree (dev->bulk_in_buffer);
kfree (dev);
}
/*设备打开函数*/
static int skel_open(struct inode *inode, struct file *file)
{
struct usb_skel *dev;//定义一个本地结构体引用
struct usb_interface *interface;//定义一个usb设备主结构体引用
int subminor;
int retval = 0;
/*在inode中的i_rdev成员中存储着设备文件的设备号，通过iminor可以从inode中获取
设备文件的次设备号*/
subminor = iminor(inode);
/*遍历驱动获取次设备号匹配的usb主设备结构体*/
interface = usb_find_interface(&skel_driver, subminor);
if (!interface) {
err ("%s - error, can't find device for minor %d",
__FUNCTION__, subminor);
retval = -ENODEV;
goto exit;
}
/*从interface中获取数据保存到dev中*/
dev = usb_get_intfdata(interface);
if (!dev) {
retval = -ENODEV;
goto exit;
}
/* increment our usage count for the device */
/*增加设备的内核使用计数*/
kref_get(&dev->kref);
/* save our object in the file's private structure */
/*将获取的本地设备保存到文件私有数据当中*/
file->private_data = dev;
exit:
return retval;
}
static int skel_release(struct inode *inode, struct file *file)
{
struct usb_skel *dev;
/*获取本地usb设备*/
dev = (struct usb_skel *)file->private_data;
if (dev == NULL)
return -ENODEV;
/* decrement the count on our device */
/*减少usb设备的内核使用计数*/
kref_put(&dev->kref, skel_delete);
return 0;
}
/*设备读函数*/
static ssize_t skel_read(struct file *file, char __user *buffer, size_t count, loff_t *ppos)
{
/*这里在读函数中我们使用无urb的方法实现数据的传输*/
struct usb_skel *dev;
int retval = 0;
//获取本地设备结构体
dev = (struct usb_skel *)file->private_data;
/* do a blocking bulk read to get data from the device */
/*从usb设备中获取数据保存到dev的bulk_in_buffer，
当然此函数也可以发送数据到usb设备当中，主要取决于第二参数是in端点还是out端点*/
retval = usb_bulk_msg(dev->udev,
usb_rcvbulkpipe(dev->udev, dev->bulk_in_endpointAddr),
dev->bulk_in_buffer,
min(dev->bulk_in_size, count),
&count, HZ*10);
/* if the read was successful, copy the data to userspace */
if (!retval) {
//将接收到的数据拷贝到用户空间
if (copy_to_user(buffer, dev->bulk_in_buffer, count))
retval = -EFAULT;
else
retval = count;
}
return retval;
}
/*urb写入完成回调函数*/
static void skel_write_bulk_callback(struct urb *urb, struct pt_regs *regs)
{
/* sync/async unlink faults aren't errors */
/*通过检查urb的状态来确定urb是否成功完成*/
if (urb->status &&
!(urb->status == -ENOENT ||
urb->status == -ECONNRESET ||
urb->status == -ESHUTDOWN)) {
dbg("%s - nonzero write bulk status received: %d",
__FUNCTION__, urb->status);
}
/* free up our allocated buffer */
/*释放安排给这个urb传送的已分配的缓冲*/
usb_buffer_free(urb->dev, urb->transfer_buffer_length,
urb->transfer_buffer, urb->transfer_dma);
}
/*字符设备写函数*/
static ssize_t skel_write(struct file *file, const char __user *user_buffer, size_t count, loff_t *ppos)
{
struct usb_skel *dev;
int retval = 0;
struct urb *urb = NULL;
char *buf = NULL;
/*获取usb本地设备结构*/
dev = (struct usb_skel *)file->private_data;
/* verify that we actually have some data to write */
if (count == 0)
goto exit;
/* create a urb, and a buffer for it, and copy the data to the urb */
/*创建一个urb*/
urb = usb_alloc_urb(0, GFP_KERNEL);
if (!urb) {
retval = -ENOMEM;
goto error;
}
/*分配一个dma缓冲buf*/
buf = usb_buffer_alloc(dev->udev, count, GFP_KERNEL, &urb->transfer_dma);
if (!buf) {
retval = -ENOMEM;
goto error;
}
/*将用户空间写入的数据拷贝到缓冲区buf中*/
if (copy_from_user(buf, user_buffer, count)) {
retval = -EFAULT;
goto error;
}
/* initialize the urb properly */
/*在urb被提交之前需要被初始化*/
/*在这里传入写入完成回调函数指针skel_write_bulk_callback*/
usb_fill_bulk_urb(urb, dev->udev,
usb_sndbulkpipe(dev->udev, dev->bulk_out_endpointAddr),
buf, count, skel_write_bulk_callback, dev);
urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;
/* send the data out the bulk port */
/*当urb的分配，数据拷贝，初始完成之后，就可以将urb提交给设备*/
retval = usb_submit_urb(urb, GFP_KERNEL);
if (retval) {
err("%s - failed submitting write urb, error %d", __FUNCTION__, retval);
goto error;
}
/* release our reference to this urb, the USB core will eventually free it entirely */
usb_free_urb(urb);
exit:
return count;
error:
usb_buffer_free(dev->udev, count, buf, urb->transfer_dma);
usb_free_urb(urb);
kfree(buf);
return retval;
}
static struct file_operations skel_fops = {
.owner = THIS_MODULE,
.read = skel_read,
.write = skel_write,
.open = skel_open,
.release = skel_release,
};
/*
* usb class driver info in order to get a minor number from the usb core,
* and to have the device registered with devfs and the driver core
*/
/**usb 类驱动 信息 使我们 能 从usb core usb核 得到一个次 设备
从而可以 使 设备被 注册 到 驱动内核中**/
static struct usb_class_driver skel_class = {
.name = "usb/skel%d",//设备结构的名称
.fops = &skel_fops,
.mode = S_IFCHR | S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH,
.minor_base = USB_SKEL_MINOR_BASE,
};
/*探测函数的写法*/
static int skel_probe(struct usb_interface *interface, const struct usb_device_id *id)
{
struct usb_skel *dev = NULL;
struct usb_host_interface *iface_desc;
struct usb_endpoint_descriptor *endpoint;
size_t buffer_size;
int i;
int retval = -ENOMEM;
/* allocate memory for our device state and initialize it */
/*为我们定义的设备结构分配内存*/
dev = kmalloc(sizeof(struct usb_skel), GFP_KERNEL);
if (dev == NULL) {
err("Out of memory");
goto error;
}
memset(dev, 0x00, sizeof (*dev));
kref_init(&dev->kref);//初始化内核引用计数
/*获取usb设备结构体*/
dev->udev = usb_get_dev(interface_to_usbdev(interface));
/*设置usb主设备结构体对象*/
dev->interface = interface;
/* set up the endpoint information */
/* use only the first bulk-in and bulk-out endpoints */
/*设置端点信息
*/
iface_desc = interface->cur_altsetting;
for (i = 0; i < iface_desc->desc.bNumEndpoints; ++i) {
endpoint = &iface_desc->endpoint[i].desc;
/*判断此端点方向是否为IN
判断此端点类型是否为块bulk*/
if (!dev->bulk_in_endpointAddr &&
(endpoint->bEndpointAddress & USB_DIR_IN) &&
((endpoint->bmAttributes & USB_ENDPOINT_XFERTYPE_MASK)
== USB_ENDPOINT_XFER_BULK)) {
/* we found a bulk in endpoint */
/*如果满足条件，将端点信息保存到本地设备结构体中*/
buffer_size = endpoint->wMaxPacketSize;
dev->bulk_in_size = buffer_size;
dev->bulk_in_endpointAddr = endpoint->bEndpointAddress;
dev->bulk_in_buffer = kmalloc(buffer_size, GFP_KERNEL);
if (!dev->bulk_in_buffer) {
err("Could not allocate bulk_in_buffer");
goto error;
}
}
if (!dev->bulk_out_endpointAddr &&
!(endpoint->bEndpointAddress & USB_DIR_IN) &&
((endpoint->bmAttributes & USB_ENDPOINT_XFERTYPE_MASK)
== USB_ENDPOINT_XFER_BULK)) {
/* we found a bulk out endpoint */
/*如果发现一个OUT块端点，将端点地址付给本地设备结构体中的相关成员*/
dev->bulk_out_endpointAddr = endpoint->bEndpointAddress;
}
}
if (!(dev->bulk_in_endpointAddr && dev->bulk_out_endpointAddr)) {
err("Could not find both bulk-in and bulk-out endpoints");
goto error;
}
/* save our data pointer in this interface device */
/*保存我们的设备数据指针到主USB设备*/
usb_set_intfdata(interface, dev);
/* we can register the device now, as it is ready */
/*现在设备已经准备好了，我们可以注册它了*/
retval = usb_register_dev(interface, &skel_class);
if (retval) {
/* something prevented us from registering this driver */
err("Not able to get a minor for this device.");
usb_set_intfdata(interface, NULL);
goto error;
}
/* let the user know what node this device is now attached to */
info("USB Skeleton device now attached to USBSkel-%d", interface->minor);
return 0;
error:
if (dev)
kref_put(&dev->kref, skel_delete);
return retval;
}
/*去连接函数*/
static void skel_disconnect(struct usb_interface *interface)
{
struct usb_skel *dev;
int minor = interface->minor;
/* prevent skel_open() from racing skel_disconnect() */
/*获取bigkernel锁，阻止open()调用*/
lock_kernel();
/*从usb主设备结构中获取信息到usb设备结构当中*/
dev = usb_get_intfdata(interface);
/*设置usb主设备为NULL*/
usb_set_intfdata(interface, NULL);
/* give back our minor */
/*注销usb设备*/
usb_deregister_dev(interface, &skel_class);
/*解除锁*/
unlock_kernel();
/* decrement our usage count */
/*减少usb使用计数，释放usb设备缓冲区*/
kref_put(&dev->kref, skel_delete);
/*打印相关信息*/
info("USB Skeleton #%d now disconnected", minor);
}
//定义并初始化usb驱动，只需要初始化这五个成员就可以了
static struct usb_driver skel_driver = {
.owner = THIS_MODULE,//指向驱动
.name = "skeleton",//驱动名字
.id_table = skel_table,//可匹配的USB类型列表
.probe = skel_probe,//指向USB驱动程序中探测函数的指针
.disconnect = skel_disconnect,//指向USB驱动中去连接函数的指针
};
/*usb模块初始化函数*/
static int __init usb_skel_init(void)
{
int result;
/* register this driver with the USB subsystem */
/*注册驱动*/
result = usb_register(&skel_driver);
if (result)
err("usb_register failed. Error number %d", result);
return result;
}
/*usb模块卸载函数*/
static void __exit usb_skel_exit(void)
{
/* deregister this driver with the USB subsystem */
/*注销usb驱动*/
usb_deregister(&skel_driver);
}
module_init (usb_skel_init);
module_exit (usb_skel_exit);
MODULE_LICENSE("GPL");