diff options
| -rw-r--r-- | drivers/usb/usb-skeleton.c | 194 |
1 files changed, 176 insertions, 18 deletions
diff --git a/drivers/usb/usb-skeleton.c b/drivers/usb/usb-skeleton.c index 60ba631e99c..5ffa3e24685 100644 --- a/drivers/usb/usb-skeleton.c +++ b/drivers/usb/usb-skeleton.c @@ -52,15 +52,21 @@ struct usb_skel { 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 */ 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 */ struct kref kref; 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) @@ -71,6 +77,7 @@ static void skel_delete(struct kref *kref) { 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); @@ -174,38 +181,182 @@ static int skel_flush(struct file *file, fl_owner_t id) 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) { struct usb_skel *dev; - int retval; - int bytes_read; + int rv; + bool ongoing_io; 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 */ - retval = -ENODEV; + rv = -ENODEV; goto exit; } - /* do a blocking bulk read to get data from the device */ - 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); - - /* 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; + /* if IO is under way, we must not touch things */ +retry: + spin_lock_irq(&dev->err_lock); + ongoing_io = dev->ongoing_read; + spin_unlock_irq(&dev->err_lock); + + if (ongoing_io) { + /* + * IO may take forever + * 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 + 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: mutex_unlock(&dev->io_mutex); - return retval; + return rv; } 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); spin_lock_init(&dev->err_lock); init_usb_anchor(&dev->submitted); + init_completion(&dev->bulk_in_completion); dev->udev = usb_get_dev(interface_to_usbdev(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"); 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 && @@ -453,6 +610,7 @@ static void skel_draw_down(struct usb_skel *dev) time = usb_wait_anchor_empty_timeout(&dev->submitted, 1000); if (!time) 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) |