V4L/DVB:usbvideo:don't use part of buffer for USB transfer #4

The status[] is part of  uvc_device structure. We can't make sure
the address of status is at a cache-line boundary in all archs,so
status[] might share a cache-line with some fields in uvc_structure.
This can lead to some cache coherence issues(http://lwn.net/Articles/2265/).
Use dynamically allocated buffer instead.

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Acked-by: Laurent Pinchart <laurent.pinchart@skynet.be>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

2 files changed, 12 insertions, 3 deletions

diff --git a/drivers/media/video/uvc/uvc_status.c b/drivers/media/video/uvc/uvc_status.c
index 75e678ac54eb..5d60b264d59a 100644
--- a/drivers/media/video/uvc/uvc_status.c
+++ b/drivers/media/video/uvc/uvc_status.c
@@ -177,9 +177,15 @@ int uvc_status_init(struct uvc_device *dev)
 
         uvc_input_init(dev);
 
+        dev->status = kzalloc(UVC_MAX_STATUS_SIZE, GFP_KERNEL);
+        if (dev->status == NULL)
+                return -ENOMEM;
+
         dev->int_urb = usb_alloc_urb(0, GFP_KERNEL);
-        if (dev->int_urb == NULL)
+        if (dev->int_urb == NULL) {
+                kfree(dev->status);
                 return -ENOMEM;
+        }
 
         pipe = usb_rcvintpipe(dev->udev, ep->desc.bEndpointAddress);
 
@@ -192,7 +198,7 @@ int uvc_status_init(struct uvc_device *dev)
                 interval = fls(interval) - 1;
 
         usb_fill_int_urb(dev->int_urb, dev->udev, pipe,
-                dev->status, sizeof dev->status, uvc_status_complete,
+                dev->status, UVC_MAX_STATUS_SIZE, uvc_status_complete,
                 dev, interval);
 
         return usb_submit_urb(dev->int_urb, GFP_KERNEL);
@@ -202,6 +208,7 @@ void uvc_status_cleanup(struct uvc_device *dev)
 {
         usb_kill_urb(dev->int_urb);
         usb_free_urb(dev->int_urb);
+        kfree(dev->status);
         uvc_input_cleanup(dev);
 }
 
diff --git a/drivers/media/video/uvc/uvcvideo.h b/drivers/media/video/uvc/uvcvideo.h
index bafe3406e305..9a6bc1aafb16 100644
--- a/drivers/media/video/uvc/uvcvideo.h
+++ b/drivers/media/video/uvc/uvcvideo.h
@@ -303,6 +303,8 @@ struct uvc_xu_control {
 #define UVC_MAX_FRAME_SIZE      (16*1024*1024)
 /* Maximum number of video buffers. */
 #define UVC_MAX_VIDEO_BUFFERS   32
+/* Maximum status buffer size in bytes of interrupt URB. */
+#define UVC_MAX_STATUS_SIZE     16
 
 #define UVC_CTRL_CONTROL_TIMEOUT        300
 #define UVC_CTRL_STREAMING_TIMEOUT      1000
@@ -634,7 +636,7 @@ struct uvc_device {
         /* Status Interrupt Endpoint */
         struct usb_host_endpoint *int_ep;
         struct urb *int_urb;
-        __u8 status[16];
+        __u8 *status;
         struct input_dev *input;
 
         /* Video Streaming interfaces */