分类： 嵌入式
2010-12-16 21:15:22
/*
* USB Skeleton driver - 2.2
*
* Copyright (C) 2001-2004 Greg Kroah-Hartman (greg@kroah.com)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation, version 2.
*
* This driver is based on the 2.6.3 version of drivers/usb/usb-skeleton.c
* but has been rewritten to be easier to read and use.
*
*/
#include
#include
#include
#include
#include
#include
#include
#include
#include
/* Define these values to match your devices */
#define USB_SKEL_VENDOR_ID 0xfff0
#define USB_SKEL_PRODUCT_ID 0xfff0
/* table of devices that work with this driver */
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
/* our private defines. if this grows any larger, use your own .h file */
#define MAX_TRANSFER (PAGE_SIZE - 512)
/* MAX_TRANSFER is chosen so that the VM is not stressed by
allocations > PAGE_SIZE and the number of packets in a page
is an integer 512 is the largest possible packet on EHCI */
#define WRITES_IN_FLIGHT 8
/* arbitrarily chosen */
/* Structure to hold all of our device specific stuff */
struct usb_skel {
struct usb_device *udev; /* the usb device for this device */
struct usb_interface *interface; /* the interface for this device */
struct semaphore limit_sem; /* limiting the number of writes in progress */
struct usb_anchor submitted; /* in case we need to retract our submissions */
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 */
int errors; /* the last request tanked */
int open_count; /* count the number of openers */
spinlock_t err_lock; /* lock for errors */
struct kref kref;
struct mutex io_mutex; /* synchronize I/O with disconnect */
};
#define to_skel_dev(d) container_of(d, struct usb_skel, kref) //通过结构体usb_skel中的kref地址获取结构体usb_skel的地址
static struct usb_driver skel_driver;
static void skel_draw_down(struct usb_skel *dev);
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);
}
static int skel_open(struct inode *inode, struct file *file)
{
struct usb_skel *dev;
struct usb_interface *interface;
int subminor;
int retval = 0;
subminor = iminor(inode);
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;
}
dev = usb_get_intfdata(interface);
if (!dev) {
retval = -ENODEV;
goto exit;
}
/* increment our usage count for the device */
kref_get(&dev->kref);
/* lock the device to allow correctly handling errors
* in resumption */
mutex_lock(&dev->io_mutex);
if (!dev->open_count++) {
retval = usb_autopm_get_interface(interface);
if (retval) {
dev->open_count--;
mutex_unlock(&dev->io_mutex);
kref_put(&dev->kref, skel_delete);
goto exit;
}
} /* else { //uncomment this block if you want exclusive open
retval = -EBUSY;
dev->open_count--;
mutex_unlock(&dev->io_mutex);
kref_put(&dev->kref, skel_delete);
goto exit;
} */
/* prevent the device from being autosuspended */
/* save our object in the file's private structure */
file->private_data = dev;
mutex_unlock(&dev->io_mutex);
exit:
return retval;
}
static int skel_release(struct inode *inode, struct file *file)
{
struct usb_skel *dev;
dev = (struct usb_skel *)file->private_data;
if (dev == NULL)
return -ENODEV;
/* allow the device to be autosuspended */
mutex_lock(&dev->io_mutex);
if (!--dev->open_count && dev->interface)
usb_autopm_put_interface(dev->interface);
mutex_unlock(&dev->io_mutex);
/* decrement the count on our device */
kref_put(&dev->kref, skel_delete);
return 0;
}
static int skel_flush(struct file *file, fl_owner_t id)
{
struct usb_skel *dev;
int res;
dev = (struct usb_skel *)file->private_data;
if (dev == NULL)
return -ENODEV;
/* wait for io to stop */
mutex_lock(&dev->io_mutex);
skel_draw_down(dev);
/* read out errors, leave subsequent opens a clean slate */
spin_lock_irq(&dev->err_lock);
res = dev->errors ? (dev->errors == -EPIPE ? -EPIPE : -EIO) : 0;
dev->errors = 0;
spin_unlock_irq(&dev->err_lock);
mutex_unlock(&dev->io_mutex);
return res;
}
//有时候USB驱动程序只是要发送或者接收一些简单的数据，驱动程序也可以不用urb来进行数据的传输，
这是里涉及到两个简单的接口函数：usb_bulk_msg和usb_control_msg ，在这个USB框架程序里读操作就是这样的一个应用：
static ssize_t skel_read(struct file *file, char *buffer, size_t count, loff_t *ppos)
{
struct usb_skel *dev;
int retval;
int bytes_read;
dev = (struct usb_skel *)file->private_data;
mutex_lock(&dev->io_mutex);
if (!dev->interface) { /* disconnect() was called */
retval = -ENODEV;
goto exit;
}
/* /* 进行阻塞的批量读以从设备获取数据 */ */
//usb_bulk_msg接口函数的定义如下：int usb_bulk_msg(struct usb_device *usb_dev,unsigned int pipe,void *data,int len,int *actual_length,int timeout);
//如果该接口函数调用成功，返回值为0，否则返回一个负的错误值
//这个接口函数都不能在一个中断上下文中或者持有自旋锁的情况下调用，同样，该函数也不能被任何其它函数取消，使用时要谨慎
retval = usb_bulk_msg(dev->udev,
usb_rcvbulkpipe(dev->udev, dev->bulk_in_endpointAddr),
dev->bulk_in_buffer,
min(dev->bulk_in_size, count),
&bytes_read, 10000);//10000：以Jiffies为单位的等待的超时时间，如果该值为0，该函数一直等待消息的结束。
/* if the read was successful, copy the data to userspace */
if (!retval) {
if (copy_to_user(buffer, dev->bulk_in_buffer, bytes_read))
retval = -EFAULT;
else
retval = bytes_read;
}
exit:
mutex_unlock(&dev->io_mutex);
return retval;
}
//当urb被成功传输到USB设备之后，urb回调函数将被USB核心调用，在我们的例子中，我们初始化urb，使它指向skel_write_bulk_callback函数，以下就是该函数：
static void skel_write_bulk_callback(struct urb *urb)
{
struct usb_skel *dev;
dev = (struct usb_skel *)urb->context;
/* sync/async unlink faults aren't errors */
if (urb->status) {
if(!(urb->status == -ENOENT ||
urb->status == -ECONNRESET ||
urb->status == -ESHUTDOWN))
err("%s - nonzero write bulk status received: %d",
__FUNCTION__, urb->status);
spin_lock(&dev->err_lock);
dev->errors = urb->status;
spin_unlock(&dev->err_lock);
}
/* free up our allocated buffer */
usb_buffer_free(urb->dev, urb->transfer_buffer_length,
urb->transfer_buffer, urb->transfer_dma);
up(&dev->limit_sem);
}
//当驱动程序有数据要发送到USB设备时（大多数情况是在驱动程序的写函数中），要分配一个urb来把数据传输给设备：
static ssize_t skel_write(struct file *file, const char *user_buffer, size_t count, loff_t *ppos)
{
struct usb_skel *dev;
int retval = 0;
struct urb *urb = NULL;
char *buf = NULL;
size_t writesize = min(count, (size_t)MAX_TRANSFER);
dev = (struct usb_skel *)file->private_data;
/* verify that we actually have some data to write */
if (count == 0)
goto exit;
/* limit the number of URBs in flight to stop a user from using up all RAM */
if (down_interruptible(&dev->limit_sem)) {
retval = -ERESTARTSYS;
goto exit;
}
spin_lock_irq(&dev->err_lock);
if ((retval = dev->errors) < 0) {
/* any error is reported once */
dev->errors = 0;
/* to preserve notifications about reset */
retval = (retval == -EPIPE) ? retval : -EIO;
}
spin_unlock_irq(&dev->err_lock);
if (retval < 0)
goto error;
//创建一个urb,并且给它分配一个缓存
/* create a urb, and a buffer for it, and copy the data to the urb */
urb = usb_alloc_urb(0, GFP_KERNEL);
if (!urb) {
retval = -ENOMEM;
goto error;
}
//当urb被成功分配后，还要创建一个DMA缓冲区来以高效的方式发送数据到设备，传递给驱动程序的数据要复制到这块缓冲中去：
buf = usb_buffer_alloc(dev->udev, writesize, GFP_KERNEL, &urb->transfer_dma);
if (!buf) {
retval = -ENOMEM;
goto error;
}
if (copy_from_user(buf, user_buffer, writesize)) {
retval = -EFAULT;
goto error;
}
/* this lock makes sure we don't submit URBs to gone devices */
mutex_lock(&dev->io_mutex);
if (!dev->interface) { /* disconnect() was called */
mutex_unlock(&dev->io_mutex);
retval = -ENODEV;
goto error;
}
//当数据从用户空间正确复制到局部缓冲区后，urb必须在可以被提交给USB核心之前被正确初始化：这时就把urb与设备端口地址及缓冲buf建立起联系了
usb_fill_bulk_urb(urb, dev->udev,
usb_sndbulkpipe(dev->udev, dev->bulk_out_endpointAddr),
buf, writesize, skel_write_bulk_callback, dev);
urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;
usb_anchor_urb(urb, &dev->submitted);// **不知道 什么作用 ？？？
/* /* 把数据从批量OUT端口发出 */ */
//然后urb就可以被提交给USB核心以传输到设备了：
retval = usb_submit_urb(urb, GFP_KERNEL);
mutex_unlock(&dev->io_mutex);
if (retval) {
err("%s - failed submitting write urb, error %d", __FUNCTION__, retval);
goto error_unanchor;
}
/* release our reference to this urb, the USB core will eventually free it entirely */
usb_free_urb(urb);
return writesize;
error_unanchor:
usb_unanchor_urb(urb);
error:
if (urb) {
usb_buffer_free(dev->udev, writesize, buf, urb->transfer_dma);
usb_free_urb(urb);
}
up(&dev->limit_sem);
exit:
return retval;
}
static const struct file_operations skel_fops = {
.owner = THIS_MODULE,
.read = skel_read,
.write = skel_write,
.open = skel_open,
.release = skel_release,
.flush = skel_flush,
};
/*
* usb class driver info in order to get a minor number from the usb core,
* and to have the device registered with the driver core
*/
static struct usb_class_driver skel_class = {
.name = "skel%d",
.fops = &skel_fops,
.minor_base = USB_SKEL_MINOR_BASE,/*给这个驱动安排的次设备号的起始. 所有和这个驱动相关的设备被创建为从这个值开始的唯一的,
递增的次设备号.只有 16 个设备被允许在任何时刻和这个驱动关联, 除非 CONFIG_USB_DYNAMIC_MINORS 配置选项被打开. 如果这样, 忽略这个变量,
并且这个设备的所有的次设备号会以先来先服务的方式分配. 建议打开了这个选项的系统使用类似 udev 的程序来产生系统中的设备节点, 因为一个静态的 /dev 树不会正确工作.*/
};
//这个是指向USB驱动程序中的探测函数的指针。当USB核心认为它有一个接口（usb_interface）可以由该驱动程序处理时，这个函数被调用。
//还有就是在探测函数中把需要探测的接口端点类型写好，在这个框架程序中只探测了批量（USB_ENDPOINT_XFER_BULK）IN和OUT端点，
//可以在此处使用掩码（USB_ENDPOINT_XFERTYPE_MASK）让其探测其它的端点类型，驱动程序会对USB设备的每一个接口进行一次探测，
//当探测成功后，驱动程序就被绑定到这个接口上。再有就是urb的初始化问题，如果你只写简单的USB驱动，这块不用多加考虑，
//框架程序里的东西已经够用了，这里我们简单介绍三个初始化urb的辅助函数：
static int skel_probe(struct usb_interface *interface, const struct usb_device_id *id)
{
struct usb_skel *dev;
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 */
dev = kzalloc(sizeof(*dev), GFP_KERNEL);
if (!dev) {
err("Out of memory");
goto error;
}
kref_init(&dev->kref);
sema_init(&dev->limit_sem, WRITES_IN_FLIGHT);
mutex_init(&dev->io_mutex);
spin_lock_init(&dev->err_lock);
init_usb_anchor(&dev->submitted);
dev->udev = usb_get_dev(interface_to_usbdev(interface));//通过interface获取udev
dev->interface = interface;
//设备中有几个interface probe函数就会执行多少次
/* set up the endpoint information */
/* use only the first bulk-in and bulk-out endpoints */
iface_desc = interface->cur_altsetting;//struct usb_host_interface *iface_desc;
for (i = 0; i < iface_desc->desc.bNumEndpoints; ++i) {
endpoint = &iface_desc->endpoint[i].desc;//获取interface中端点
if (!dev->bulk_in_endpointAddr &&
usb_endpoint_is_bulk_in(endpoint)) {//发现一个bulk的端点
/* we found a bulk in endpoint */
buffer_size = le16_to_cpu(endpoint->wMaxPacketSize);//获取bulk_buffer的大小
dev->bulk_in_size = buffer_size;
dev->bulk_in_endpointAddr = endpoint->bEndpointAddress;//获取端点的地址
dev->bulk_in_buffer = kmalloc(buffer_size, GFP_KERNEL);//分配bulk_buffer的空间
if (!dev->bulk_in_buffer) {
err("Could not allocate bulk_in_buffer");
goto error;
}
}
if (!dev->bulk_out_endpointAddr &&
usb_endpoint_is_bulk_out(endpoint)) {
/* we found a bulk out endpoint */
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 */
usb_set_intfdata(interface, dev);//把我们分配的dev地址保存到interface中，即可以通过interface找到我们定义的dev
/* we can register the device now, as it is ready */
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)
/* this frees allocated memory */
kref_put(&dev->kref, skel_delete);
return retval;
}
//指向USB驱动程序中的断开函数的指针，当一个USB接口（usb_interface）被从系统中移除或者驱动程序正在从USB核心中卸载时，USB核心将调用这个函数。
static void skel_disconnect(struct usb_interface *interface)
{
struct usb_skel *dev;
int minor = interface->minor;
dev = usb_get_intfdata(interface);
usb_set_intfdata(interface, NULL);//把interface中包含dev地址信息抹去
/* give back our minor */
usb_deregister_dev(interface, &skel_class);
/* prevent more I/O from starting */
mutex_lock(&dev->io_mutex);
dev->interface = NULL;
mutex_unlock(&dev->io_mutex);
usb_kill_anchored_urbs(&dev->submitted);//强制取消所有的urb
/* decrement our usage count */
kref_put(&dev->kref, skel_delete);
info("USB Skeleton #%d now disconnected", minor);
}
//等待所有提交的urb完成，如果超时候，强制取消所有的urb
static void skel_draw_down(struct usb_skel *dev)
{
int time;
time = usb_wait_anchor_empty_timeout(&dev->submitted, 1000);
if (!time)
usb_kill_anchored_urbs(&dev->submitted);
}
/*指向 USB 驱动中挂起函数的指针*/
static int skel_suspend(struct usb_interface *intf, pm_message_t message)
{
struct usb_skel *dev = usb_get_intfdata(intf);
if (!dev)
return 0;
skel_draw_down(dev);
return 0;
}
/*指向 USB 驱动中恢复函数的指针*/
static int skel_resume (struct usb_interface *intf)
{
return 0;
}
/*在设备被复位之前由usb_reset_composite_device()调用*/
static int skel_pre_reset(struct usb_interface *intf)
{
struct usb_skel *dev = usb_get_intfdata(intf);
mutex_lock(&dev->io_mutex);
skel_draw_down(dev);
return 0;
}
/*在设备被复位之后由usb_reset_composite_device()调用*/
static int skel_post_reset(struct usb_interface *intf)
{
struct usb_skel *dev = usb_get_intfdata(intf);
/* we are sure no URBs are active - no locking needed */
dev->errors = -EPIPE;
mutex_unlock(&dev->io_mutex);
return 0;
}
static struct usb_driver skel_driver = {
.name = "skeleton",
.probe = skel_probe,
.disconnect = skel_disconnect,
.suspend = skel_suspend,
.resume = skel_resume,
.pre_reset = skel_pre_reset,
.post_reset = skel_post_reset,
.id_table = skel_table,
.supports_autosuspend = 1,
};
static int __init usb_skel_init(void)
{
int result;
/* register this driver with the USB subsystem */
result = usb_register(&skel_driver);////向 USB 核心注册 struct usb_driver
if (result)
err("usb_register failed. Error number %d", result);
return result;
}
static void __exit usb_skel_exit(void)
{
/* deregister this driver with the USB subsystem */
usb_deregister(&skel_driver);
}
module_init(usb_skel_init);
module_exit(usb_skel_exit);
MODULE_LICENSE("GPL");
usb_fill_int_urb ：它的函数原型是这样的：
void usb_fill_int_urb(struct urb *urb,struct usb_device *dev,
unsigned int pipe,void *transfer_buff,
int buffer_length,usb_complete_t complete,
void *context,int interval);
这个函数用来正确的初始化即将被发送到USB设备的中断端点的urb。
usb_fill_bulk_urb ：它的函数原型是这样的：
void usb_fill_bulk_urb(struct urb *urb,struct usb_device *dev,
unsigned int pipe,void *transfer_buffer,
int buffer_length,usb_complete_t complete)
这个函数是用来正确的初始化批量urb端点的。
usb_fill_control_urb ：它的函数原型是这样的：
void usb_fill_control_urb(struct urb *urb,struct usb_device *dev,unsigned int pipe,unsigned char *setup_packet,void *transfer_buffer,int buffer_length,usb_complete_t complete,void *context);
这个函数是用来正确初始化控制urb端点的。
还有一个初始化等时urb的，它现在还没有初始化函数，所以它们在被提交到USB核心前，必须在驱动程序中手工地进行初始化，可以参考内核源代码树下的/usr/src/~/drivers/usb/media下的konicawc.c文件。
其中xxx是源文件的文件名，在linux下直接执行make就可以生成驱动模块（xxx.ko）了。生成驱动模块后使用insmod xxx.ko就可以插入到内核中运行了，用lsmod可以看到你插入到内核中的模块，也可以从系统中用命令rmmod xxx把模块卸载掉；
如果把编译出来的驱动模块拷贝到/lib/modules/~/kernel/drivers/usb/下，然后depmod一下，那么你在插入USB设备的时候，系统就会自动为你加载驱动模块的；当然这个得有hotplug的支持；加载驱动模块成功后就会在/dev/下生成设备文件了，
如果用命令cat /proc/bus/usb/devices，我们可以看到驱动程序已经绑定到接口上了：
T: Bus=03 Lev=01 Prnt=01 Port=01 Cnt=01 Dev#= 2 Spd=12 MxCh= 0
D: Ver= 1.10 Cls=02(comm.) Sub=00 Prot=00 MxPS= 8 #Cfgs= 1
P: Vendor=1234 ProdID=2345 Rev= 1.10
C:* #Ifs= 1 Cfg#= 1 Atr=c0 MxPwr= 0mA
I: If#= 1 Alt= 0 #EPs= 2 Cls=0a(data ) Sub=00 Prot=00 Driver=test_usb_driver /*我们的驱动*/
E: Ad=01(O) Atr=02(Bulk) MxPS= 64 Ivl=0ms
E: Ad=82(I) Atr=02(Bulk) MxPS= 64 Ivl=0ms
此框架程序生成的是skel0（可以自由修改）的设备文件，现在就可以对这个设备文件进行打开、读写、关闭等的操作了。
