Linux裝置驅動開發---USB主機(控制器)與裝置驅動（三）
阿新 • • 發佈：2020-12-31
技術標籤：嵌入式linuxusb skeletonskelurbusb driverhcd
USB主機控制器與裝置驅動---主機側
- 一、Linux USB驅動層次
- 二、USB主機(控制器)驅動
- 三、USB裝置驅動
- 3.4 USB骨架程式(詳解)
- 10）編寫skel_delete函式(減少引用計數時使用)
- 9）編寫skel_write及其完成函式；
- 8）編寫skel_read及依賴函式
- 7）編寫skel_open和skel_release函式
- 6）定義skel_class裡的成員函式；
- 5）定義usb_class_driver結構體skel_class(probe和disconnect函式中註冊/登出usb裝置時需傳入)；
- 4）編寫skel_probe和skel_disconnect函式；
- 3）定義特定的裝置資料結構；
- 2）定義裝置id，初始化skel_table，並匯入到使用者空間；
- 1）初始化usb_driver結構體skel_driver，並註冊該usb driver；
一、Linux USB驅動層次
二、USB主機(控制器)驅動
三、USB裝置驅動
3.4 USB骨架程式(詳解)
File path: drivers/usb/usb-skeleton.c（省略部分返回值判斷及部分程式碼）
10）編寫skel_delete函式(減少引用計數時使用)
#define to_skel_dev(d) container_of(d, struct usb_skel, kref)
static void skel_delete(struct kref *kref)
{
/*獲取usb_skel整個變數的資料*/
struct usb_skel *dev = to_skel_dev(kref);
usb_free_urb(dev->bulk_in_urb);
usb_put_dev(dev->udev);
kfree(dev->bulk_in_buffer);
kfree(dev);
}
9）編寫skel_write及其完成函式；
9.2）static void skel_write_bulk_callback(struct urb *urb)
{
struct usb_skel *dev;
dev = urb->context;
/*sync/async去除鏈路故障都不是errors*/
if (urb->status) {
if (!(urb->status == -ENOENT ||
urb->status == -ECONNRESET ||
urb->status == -ESHUTDOWN))
dev_err(&dev->interface->dev, "%s - nonzero write bulk status received: %d\n",
__func__, urb->status);
spin_lock(&dev->err_lock);
dev->errors = urb->status;
spin_unlock(&dev->err_lock);
}
/*釋放分配的buffer*/
usb_free_coherent(urb->dev, urb->transfer_buffer_length,
urb->transfer_buffer, urb->transfer_dma);
up(&dev->limit_sem);
}
9.1）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);
/*1. 獲取介面資料*/
dev = file->private_data;
/*2. 若無資料可寫，則直接返回*/
if (count == 0)
goto exit;
/*3. 限制urb的數量，防止將RAM全部用完*/
if (!(file->f_flags & O_NONBLOCK)) {
if (down_interruptible(&dev->limit_sem)) {
retval = -ERESTARTSYS;
goto exit;
}
} else {
if (down_trylock(&dev->limit_sem)) {
retval = -EAGAIN;
goto exit;
}
}
/*4. 報告errors*/
spin_lock_irq(&dev->err_lock);
retval = dev->errors;
if (retval < 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;
/*5. 建立一個urb和buffer，然後複製資料到該urb*/
urb = usb_alloc_urb(0, GFP_KERNEL);
if (!urb) {
retval = -ENOMEM;
goto error;
}
buf = usb_alloc_coherent(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;
}
/*6. 確保不會將urb提交到已移除的device*/
mutex_lock(&dev->io_mutex);
if (!dev->interface) { /* disconnect() was called */
mutex_unlock(&dev->io_mutex);
retval = -ENODEV;
goto error;
}
/*7. 合適的初始化該urb*/
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);
/*8. 傳送資料到批量埠*/
retval = usb_submit_urb(urb, GFP_KERNEL);
mutex_unlock(&dev->io_mutex);
if (retval) {
dev_err(&dev->interface->dev,"%s - failed submitting write urb, error %d\n",
__func__, retval);
goto error_unanchor;
}
/*9. 釋放對這個urb的引用，USB core會最終完全釋放*/
usb_free_urb(urb);
return writesize;
error_unanchor:
usb_unanchor_urb(urb);
error:
if (urb) {
usb_free_coherent(dev->udev, writesize, buf, urb->transfer_dma);
usb_free_urb(urb);
}
up(&dev->limit_sem);
exit:
return retval;
}
8）編寫skel_read及依賴函式
8.3）讀操作完成函式
static void skel_read_bulk_callback(struct urb *urb)
{
struct usb_skel *dev;
dev = urb->context;
spin_lock(&dev->err_lock);
if (urb->status) {
if (!(urb->status == -ENOENT || urb->status == -ECONNRESET ||urb->status == -ESHUTDOWN))
dev_err(&dev->interface->dev, "%s - nonzero write bulk status received: %d\n",
__func__, urb->status);
dev->errors = urb->status;
}else{
//傳輸成功
dev->bulk_in_filled = urb->actual_length;
}
dev->ongoing_read = 0;
spin_unlock(&dev->err_lock);
wake_up_interruptible(&dev->bulk_in_wait);
}
8.2）static int skel_do_read_io(struct usb_skel *dev, size_t count)
{
int rv;
/*1. 初始化urb*/
usb_fill_bulk_urb(dev->bulk_in_urb, dev->udev, usb_rcvbulkpipe(dev->udev,dev->bulk_in_endpointAddr),
dev->bulk_in_buffer, min(dev->bulk_in_size, count), skel_read_bulk_callback, dev);
/*2. 告訴其他程序正在進行讀操作*/
spin_lock_irq(&dev->err_lock);
dev->ongoing_read = 1;
spin_unlock_irq(&dev->err_lock);
/*3. 提交urb到usb核心層*/
dev->bulk_in_filled = 0;
dev->bulk_in_copied = 0;
rv = usb_submit_urb(dev->bulk_in_urb, GFP_KERNEL);
if (rv < 0) {
dev_err(&dev->interface->dev, "%s - failed submitting read urb, error %d\n",
__func__, rv);
rv = (rv == -ENOMEM) ? rv : -EIO;
spin_lock_irq(&dev->err_lock);
dev->ongoing_read = 0;
spin_unlock_irq(&dev->err_lock);
}
return rv;
}
8.1）static ssize_t skel_read(struct file *file, char *buffer, size_t count, loff_t *ppos)
{
struct usb_skel *dev;
int rv;
bool ongoing_io;
/*1. 獲取介面資料*/
dev = file->private_data;
/*2. 如果什麼也讀不到，返回EOF*/
if (!dev->bulk_in_urb || !count)
return 0;
/*3. 確保沒有併發讀操作*/
rv = mutex_lock_interruptible(&dev->io_mutex);
if (rv < 0)
return rv;
/*4. 檢查裝置是否有介面*/
if (!dev->interface) { //disconnect() was called
rv = -ENODEV;
goto exit;
}
/*5. 如果IO在執行，就不能touch things*/
retry:
spin_lock_irq(&dev->err_lock);
ongoing_io = dev->ongoing_read;
spin_unlock_irq(&dev->err_lock);
if (ongoing_io) {
if (file->f_flags & O_NONBLOCK) { //如果時非阻塞，IO則不會wait
rv = -EAGAIN;
goto exit;
}
//否則，IO會一直等待中斷狀態
rv = wait_event_interruptible(dev->bulk_in_wait, (!dev->ongoing_read));
if (rv < 0)
goto exit;
}
/*6. 報告errors*/
rv = dev->errors;
if (rv < 0) {
dev->errors = 0;
rv = (rv == -EPIPE) ? rv : -EIO;
goto exit;
}
/*7. 如果buffer已被填充，就可以進行讀操作了；否則需要啟動IO*/
if (dev->bulk_in_filled) {
size_t available = dev->bulk_in_filled - dev->bulk_in_copied;
size_t chunk = min(available, count);
if(!available){
rv = skel_do_read_io(dev, count);
if (rv < 0)
goto exit;
else
goto retry;
}
if (copy_to_user(buffer, dev->bulk_in_buffer + dev->bulk_in_copied, chunk)) //複製user space
rv = -EFAULT;
else
rv = chunk;
dev->bulk_in_copied += chunk;
if (available < count) //如果要讀的count大於可讀的數量
skel_do_read_io(dev, count - chunk);
}else {
//無資料可讀
rv = skel_do_read_io(dev, count);
if (rv < 0)
goto exit;
else
goto retry;
}
exit:
mutex_unlock(&dev->io_mutex);
return rv;
}
7）編寫skel_open和skel_release函式
static int skel_open(struct inode *inode, struct file *file)
{
struct usb_skel *dev;
struct usb_interface *interface;
int subminor;
int retval = 0;
/*1. 獲取裝置介面*/
subminor = iminor(inode);
interface = usb_find_interface(&skel_driver, subminor);
if (!interface) {
pr_err("%s - error, can't find device for minor %d\n", __func__, subminor);
retval = -ENODEV;
goto exit;
}
/*2. 獲取介面資料*/
dev = usb_get_intfdata(interface);
if(!dev) {
retval = -ENODEV;
goto exit;
}
/*3. 增加usb介面的PM-usage計數*/
retval = usb_autopm_get_interface(interface);
if (retval)
goto exit;
/*4. 增加引用計數*/
kref_get(&dev->kref);
/*5. 儲存介面資料到file->private_data*/
file->private_data = dev;
exit:
return retval;
}
static int skel_release(struct inode *inode, struct file *file)
{
struct usb_skel *dev;
/*1. 獲取介面資料*/
dev = file->private_data;
if (dev == NULL)
return -ENODEV;
/*2. 減少usb介面的PM-usage計數*/
mutex_lock(&dev->io_mutex);
if (dev->interface)
usb_autopm_put_interface(dev->interface);
mutex_unlock(&dev->io_mutex);
/*3. 減少引用計數*/
kref_put(&dev->kref, skel_delete);
return 0;
}
6）定義skel_class裡的成員函式；
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,
.llseek = noop_llseek,
};
5）定義usb_class_driver結構體skel_class(probe和disconnect函式中註冊/登出usb裝置時需傳入)；
static struct usb_class_driver skel_class = {
.name = "skel%d",
.fops = &skel_fops,
.minor_base = USB_SKEL_MINOR_BASE,
};
4）編寫skel_probe和skel_disconnect函式；
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;
/*1. 為裝置分配記憶體並初始化裝置*/
dev = kzalloc(sizeof(*dev), GFP_KERNEL);
...
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);
init_waitqueue_head(&dev->bulk_in_wait);
dev->udev = usb_get_dev(interface_to_usbdev(interface));
dev->interface = interface;
/*2. set up端點資訊*/
/*僅使用第一個bulk-in和bulk-out端點*/
iface_desc = interface->cur_altsetting;
for (i = 0; i < iface_desc->desc.bNumEndpoints; ++i) {
endpoint = &iface_desc->endpoint[i].desc;
if (!dev->bulk_in_endpointAddr && usb_endpoint_is_bulk_in(endpoint)) {
buffer_size = usb_endpoint_maxp(endpoint);
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)
...
dev->bulk_in_urb = usb_alloc_urb(0, GFP_KERNEL);
if (!dev->bulk_in_urb)
...
}
if (!dev->bulk_out_endpointAddr && usb_endpoint_is_bulk_out(endpoint)) {
dev->bulk_out_endpointAddr = endpoint->bEndpointAddress;
}
}
if (!(dev->bulk_in_endpointAddr && dev->bulk_out_endpointAddr)) {
dev_err(&interface->dev, "Could not find both bulk-in and bulk-out endpoints\n");
...
}
/*3. 儲存資料指標到該介面裝置*/
usb_set_intfdata(interface, dev);
/*4. 註冊該裝置*/
retval = usb_register_dev(interface, &skel_class);
if (retval) {
dev_err(&interface->dev, "Not able to get a minor for this device.\n");
usb_set_intfdata(interface, NULL);
...
}
/*4. 列印裝置節點*/
dev_info(&interface->dev,"USB Skeleton device now attached to USBSkel-%d",
interface->minor);
return 0;
}
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);
/*1. 登出該usb裝置，釋放次裝置號*/
usb_deregister_dev(interface, &skel_class);
/*2. 阻止更多的I/O啟動*/
mutex_lock(&dev->io_mutex);
dev->interface = NULL;
mutex_unlock(&dev->io_mutex);
usb_kill_anchored_urbs(&dev->submitted);
/*3. 減少引用計數*/
kref_put(&dev->kref, skel_delete);
dev_info(&interface->dev, "USB Skeleton #%d now disconnected", minor);
}
3）定義特定的裝置資料結構；
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 */
struct urb *bulk_in_urb; /* the urb to read data with */
unsigned char *bulk_in_buffer; /* the buffer to receive data */
size_t bulk_in_size; /* the size of the receive buffer */
size_t bulk_in_filled; /* number of bytes in the buffer */
size_t bulk_in_copied; /* already copied to user space */
__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 */
bool ongoing_read; /* a read is going on */
spinlock_t err_lock; /* lock for errors */
struct kref kref;
struct mutex io_mutex; /* synchronize I/O with disconnect */
wait_queue_head_t bulk_in_wait; /* to wait for an ongoing read */
};
2）定義裝置id，初始化skel_table，並匯入到使用者空間；
/*定義該裝置vendor id和product id*/
#define USB_SKEL_VENDOR_ID 0xfff0
#define USB_SKEL_PRODUCT_ID 0xfff0
static const struct usb_device_id skel_table[] = {
{ USB_DEVICE(USB_SKEL_VENDOR_ID, USB_SKEL_PRODUCT_ID) },
{ } /* Terminating entry */
};
MODULE_DEVICE_TABLE(usb, skel_table);
1）初始化usb_driver結構體skel_driver，並註冊該usb driver；
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,
};
module_usb_driver(skel_driver);