diff options
| -rw-r--r-- | drivers/usb/misc/usblcd.c | 22 |
1 files changed, 18 insertions, 4 deletions
diff --git a/drivers/usb/misc/usblcd.c b/drivers/usb/misc/usblcd.c index 887ef953f3d8..12bad8a205a7 100644 --- a/drivers/usb/misc/usblcd.c +++ b/drivers/usb/misc/usblcd.c @@ -42,10 +42,14 @@ struct usb_lcd { 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; + struct kref kref; + struct semaphore limit_sem; /* to stop writes at full throttle from + * using up all RAM */ }; #define to_lcd_dev(d) container_of(d, struct usb_lcd, kref) +#define USB_LCD_CONCURRENT_WRITES 5 + static struct usb_driver lcd_driver; static DEFINE_MUTEX(usb_lcd_open_mutex); @@ -186,12 +190,13 @@ static void lcd_write_bulk_callback(struct urb *urb) /* free up our allocated buffer */ usb_buffer_free(urb->dev, urb->transfer_buffer_length, urb->transfer_buffer, urb->transfer_dma); + up(&dev->limit_sem); } static ssize_t lcd_write(struct file *file, const char __user * user_buffer, size_t count, loff_t *ppos) { struct usb_lcd *dev; - int retval = 0; + int retval = 0, r; struct urb *urb = NULL; char *buf = NULL; @@ -201,10 +206,16 @@ static ssize_t lcd_write(struct file *file, const char __user * user_buffer, siz if (count == 0) goto exit; + r = down_interruptible(&dev->limit_sem); + if (r < 0) + return -EINTR; + /* create a urb, and a buffer for it, and copy the data to the urb */ urb = usb_alloc_urb(0, GFP_KERNEL); - if (!urb) - return -ENOMEM; + if (!urb) { + retval = -ENOMEM; + goto err_no_buf; + } buf = usb_buffer_alloc(dev->udev, count, GFP_KERNEL, &urb->transfer_dma); if (!buf) { @@ -239,6 +250,8 @@ exit: error: usb_buffer_free(dev->udev, count, buf, urb->transfer_dma); usb_free_urb(urb); +err_no_buf: + up(&dev->limit_sem); return retval; } @@ -277,6 +290,7 @@ static int lcd_probe(struct usb_interface *interface, const struct usb_device_id goto error; } kref_init(&dev->kref); + sema_init(&dev->limit_sem, USB_LCD_CONCURRENT_WRITES); dev->udev = usb_get_dev(interface_to_usbdev(interface)); dev->interface = interface; |