USB: skel_read really sucks royally (e7389cc9) · Commits · 戴 / test

drivers/usb/usb-skeleton.c

+176 −18

Original line number	Original line	Diff line number	Diff line
	@@ -52,15 +52,21 @@ struct usb_skel {
	struct usb_interface interface; / the interface for this device */		struct usb_interface interface; / the interface for this device */
	struct semaphore limit_sem; /* limiting the number of writes in progress */		struct semaphore limit_sem; /* limiting the number of writes in progress */
	struct usb_anchor submitted; /* in case we need to retract our submissions */		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 */		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_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_in_endpointAddr; /* the address of the bulk in endpoint */
	__u8 bulk_out_endpointAddr; /* the address of the bulk out endpoint */		__u8 bulk_out_endpointAddr; /* the address of the bulk out endpoint */
	int errors; /* the last request tanked */		int errors; /* the last request tanked */
	int open_count; /* count the number of openers */		int open_count; /* count the number of openers */
			bool ongoing_read; /* a read is going on */
			bool processed_urb; /* indicates we haven't processed the urb */
	spinlock_t err_lock; /* lock for errors */		spinlock_t err_lock; /* lock for errors */
	struct kref kref;		struct kref kref;
	struct mutex io_mutex; /* synchronize I/O with disconnect */		struct mutex io_mutex; /* synchronize I/O with disconnect */
			struct completion bulk_in_completion; /* to wait for an ongoing read */
	};		};
	#define to_skel_dev(d) container_of(d, struct usb_skel, kref)		#define to_skel_dev(d) container_of(d, struct usb_skel, kref)

	@@ -71,6 +77,7 @@ static void skel_delete(struct kref *kref)
	{		{
	struct usb_skel *dev = to_skel_dev(kref);		struct usb_skel *dev = to_skel_dev(kref);

			usb_free_urb(dev->bulk_in_urb);
	usb_put_dev(dev->udev);		usb_put_dev(dev->udev);
	kfree(dev->bulk_in_buffer);		kfree(dev->bulk_in_buffer);
	kfree(dev);		kfree(dev);
	@@ -174,38 +181,182 @@ static int skel_flush(struct file *file, fl_owner_t id)
	return res;		return res;
	}		}

			static void skel_read_bulk_callback(struct urb *urb)
			{
			struct usb_skel *dev;

			dev = urb->context;

			spin_lock(&dev->err_lock);
			/* 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",
			__func__, urb->status);

			dev->errors = urb->status;
			} else {
			dev->bulk_in_filled = urb->actual_length;
			}
			dev->ongoing_read = 0;
			spin_unlock(&dev->err_lock);

			complete(&dev->bulk_in_completion);
			}

			static int skel_do_read_io(struct usb_skel *dev, size_t count)
			{
			int rv;

			/* prepare a read */
			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);
			/* tell everybody to leave the URB alone */
			spin_lock_irq(&dev->err_lock);
			dev->ongoing_read = 1;
			spin_unlock_irq(&dev->err_lock);

			/* do it */
			rv = usb_submit_urb(dev->bulk_in_urb, GFP_KERNEL);
			if (rv < 0) {
			err("%s - failed submitting read urb, error %d",
			__func__, rv);
			dev->bulk_in_filled = 0;
			rv = (rv == -ENOMEM) ? rv : -EIO;
			spin_lock_irq(&dev->err_lock);
			dev->ongoing_read = 0;
			spin_unlock_irq(&dev->err_lock);
			}

			return rv;
			}

	static ssize_t skel_read(struct file file, char buffer, size_t count, loff_t *ppos)		static ssize_t skel_read(struct file file, char buffer, size_t count, loff_t *ppos)
	{		{
	struct usb_skel *dev;		struct usb_skel *dev;
	int retval;		int rv;
	int bytes_read;		bool ongoing_io;

	dev = (struct usb_skel *)file->private_data;		dev = (struct usb_skel *)file->private_data;

	mutex_lock(&dev->io_mutex);		/* if we cannot read at all, return EOF */
			if (!dev->bulk_in_urb \|\| !count)
			return 0;

			/* no concurrent readers */
			rv = mutex_lock_interruptible(&dev->io_mutex);
			if (rv < 0)
			return rv;

	if (!dev->interface) { /* disconnect() was called */		if (!dev->interface) { /* disconnect() was called */
	retval = -ENODEV;		rv = -ENODEV;
	goto exit;		goto exit;
	}		}

	/* do a blocking bulk read to get data from the device */		/* if IO is under way, we must not touch things */
	retval = usb_bulk_msg(dev->udev,		retry:
	usb_rcvbulkpipe(dev->udev, dev->bulk_in_endpointAddr),		spin_lock_irq(&dev->err_lock);
	dev->bulk_in_buffer,		ongoing_io = dev->ongoing_read;
	min(dev->bulk_in_size, count),		spin_unlock_irq(&dev->err_lock);
	&bytes_read, 10000);

	/* if the read was successful, copy the data to userspace */		if (ongoing_io) {
	if (!retval) {		/*
	if (copy_to_user(buffer, dev->bulk_in_buffer, bytes_read))		* IO may take forever
	retval = -EFAULT;		* hence wait in an interruptible state
			*/
			rv = wait_for_completion_interruptible(&dev->bulk_in_completion);
			if (rv < 0)
			goto exit;
			/*
			* by waiting we also semiprocessed the urb
			* we must finish now
			*/
			dev->bulk_in_copied = 0;
			dev->processed_urb = 1;
			}

			if (!dev->processed_urb) {
			/*
			* the URB hasn't been processed
			* do it now
			*/
			wait_for_completion(&dev->bulk_in_completion);
			dev->bulk_in_copied = 0;
			dev->processed_urb = 1;
			}

			/* errors must be reported */
			if ((rv = dev->errors) < 0) {
			/* any error is reported once */
			dev->errors = 0;
			/* to preserve notifications about reset */
			rv = (rv == -EPIPE) ? rv : -EIO;
			/* no data to deliver */
			dev->bulk_in_filled = 0;
			/* report it */
			goto exit;
			}

			/*
			* if the buffer is filled we may satisfy the read
			* else we need to start IO
			*/

			if (dev->bulk_in_filled) {
			/* we had read data */
			size_t available = dev->bulk_in_filled - dev->bulk_in_copied;
			size_t chunk = min(available, count);

			if (!available) {
			/*
			* all data has been used
			* actual IO needs to be done
			*/
			rv = skel_do_read_io(dev, count);
			if (rv < 0)
			goto exit;
	else		else
	retval = bytes_read;		goto retry;
	}		}
			/*
			* data is available
			* chunk tells us how much shall be copied
			*/

			if (copy_to_user(buffer,
			dev->bulk_in_buffer + dev->bulk_in_copied,
			chunk))
			rv = -EFAULT;
			else
			rv = chunk;

			dev->bulk_in_copied += chunk;

			/*
			* if we are asked for more than we have,
			* we start IO but don't wait
			*/
			if (available < count)
			skel_do_read_io(dev, count - chunk);
			} else {
			/* no data in the buffer */
			rv = skel_do_read_io(dev, count);
			if (rv < 0)
			goto exit;
			else
			goto retry;
			}
	exit:		exit:
	mutex_unlock(&dev->io_mutex);		mutex_unlock(&dev->io_mutex);
	return retval;		return rv;
	}		}

	static void skel_write_bulk_callback(struct urb *urb)		static void skel_write_bulk_callback(struct urb *urb)
	@@ -363,6 +514,7 @@ static int skel_probe(struct usb_interface *interface, const struct usb_device_i
	mutex_init(&dev->io_mutex);		mutex_init(&dev->io_mutex);
	spin_lock_init(&dev->err_lock);		spin_lock_init(&dev->err_lock);
	init_usb_anchor(&dev->submitted);		init_usb_anchor(&dev->submitted);
			init_completion(&dev->bulk_in_completion);

	dev->udev = usb_get_dev(interface_to_usbdev(interface));		dev->udev = usb_get_dev(interface_to_usbdev(interface));
	dev->interface = interface;		dev->interface = interface;
	@@ -384,6 +536,11 @@ static int skel_probe(struct usb_interface *interface, const struct usb_device_i
	err("Could not allocate bulk_in_buffer");		err("Could not allocate bulk_in_buffer");
	goto error;		goto error;
	}		}
			dev->bulk_in_urb = usb_alloc_urb(0, GFP_KERNEL);
			if (!dev->bulk_in_urb) {
			err("Could not allocate bulk_in_urb");
			goto error;
			}
	}		}

	if (!dev->bulk_out_endpointAddr &&		if (!dev->bulk_out_endpointAddr &&
	@@ -453,6 +610,7 @@ static void skel_draw_down(struct usb_skel *dev)
	time = usb_wait_anchor_empty_timeout(&dev->submitted, 1000);		time = usb_wait_anchor_empty_timeout(&dev->submitted, 1000);
	if (!time)		if (!time)
	usb_kill_anchored_urbs(&dev->submitted);		usb_kill_anchored_urbs(&dev->submitted);
			usb_kill_urb(dev->bulk_in_urb);
	}		}

	static int skel_suspend(struct usb_interface *intf, pm_message_t message)		static int skel_suspend(struct usb_interface *intf, pm_message_t message)

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