V4L/DVB (10295): uvcvideo: Retry URB buffers allocation when the system is low on memory.

URB buffers for video transfers are sized to UVC_MAX_PACKETS bulk/isochronous
packets by default. If the system is too low on memory try successively
smaller numbers of packets until allocation succeeds.

Tested-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Laurent Pinchart <laurent.pinchart@skynet.be>
Reviewed-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

2 files changed, 44 insertions, 41 deletions

diff --git a/drivers/media/video/uvc/uvc_video.c b/drivers/media/video/uvc/uvc_video.c
index 9bc4705be78d..7ebb89539c36 100644
--- a/drivers/media/video/uvc/uvc_video.c
+++ b/drivers/media/video/uvc/uvc_video.c
@@ -699,27 +699,47 @@ static void uvc_free_urb_buffers(struct uvc_video_device *video)
  * already allocated when resuming from suspend, in which case it will
  * return without touching the buffers.
  *
- * Return 0 on success or -ENOMEM when out of memory.
+ * Limit the buffer size to UVC_MAX_PACKETS bulk/isochronous packets. If the
+ * system is too low on memory try successively smaller numbers of packets
+ * until allocation succeeds.
+ *
+ * Return the number of allocated packets on success or 0 when out of memory.
  */
 static int uvc_alloc_urb_buffers(struct uvc_video_device *video,
-        unsigned int size)
+        unsigned int size, unsigned int psize, gfp_t gfp_flags)
 {
+        unsigned int npackets;
         unsigned int i;
 
         /* Buffers are already allocated, bail out. */
         if (video->urb_size)
                 return 0;
 
-        for (i = 0; i < UVC_URBS; ++i) {
-                video->urb_buffer[i] = usb_buffer_alloc(video->dev->udev,
-                        size, GFP_KERNEL, &video->urb_dma[i]);
-                if (video->urb_buffer[i] == NULL) {
-                        uvc_free_urb_buffers(video);
-                        return -ENOMEM;
+        /* Compute the number of packets. Bulk endpoints might transfer UVC
+         * payloads accross multiple URBs.
+         */
+        npackets = DIV_ROUND_UP(size, psize);
+        if (npackets > UVC_MAX_PACKETS)
+                npackets = UVC_MAX_PACKETS;
+
+        /* Retry allocations until one succeed. */
+        for (; npackets > 1; npackets /= 2) {
+                for (i = 0; i < UVC_URBS; ++i) {
+                        video->urb_buffer[i] = usb_buffer_alloc(
+                                video->dev->udev, psize * npackets,
+                                gfp_flags | __GFP_NOWARN, &video->urb_dma[i]);
+                        if (!video->urb_buffer[i]) {
+                                uvc_free_urb_buffers(video);
+                                break;
+                        }
+                }
+
+                if (i == UVC_URBS) {
+                        video->urb_size = psize * npackets;
+                        return npackets;
                 }
         }
 
-        video->urb_size = size;
         return 0;
 }
 
@@ -753,29 +773,19 @@ static int uvc_init_video_isoc(struct uvc_video_device *video,
 {
         struct urb *urb;
         unsigned int npackets, i, j;
-        __u16 psize;
-        __u32 size;
+        u16 psize;
+        u32 size;
 
-        /* Compute the number of isochronous packets to allocate by dividing
-         * the maximum video frame size by the packet size. Limit the result
-         * to UVC_MAX_ISO_PACKETS.
-         */
         psize = le16_to_cpu(ep->desc.wMaxPacketSize);
         psize = (psize & 0x07ff) * (1 + ((psize >> 11) & 3));
-
         size = video->streaming->ctrl.dwMaxVideoFrameSize;
-        if (size > UVC_MAX_FRAME_SIZE)
-                return -EINVAL;
 
-        npackets = DIV_ROUND_UP(size, psize);
-        if (npackets > UVC_MAX_ISO_PACKETS)
-                npackets = UVC_MAX_ISO_PACKETS;
+        npackets = uvc_alloc_urb_buffers(video, size, psize, gfp_flags);
+        if (npackets == 0)
+                return -ENOMEM;
 
         size = npackets * psize;
 
-        if (uvc_alloc_urb_buffers(video, size) < 0)
-                return -ENOMEM;
-
         for (i = 0; i < UVC_URBS; ++i) {
                 urb = usb_alloc_urb(npackets, gfp_flags);
                 if (urb == NULL) {
@@ -814,25 +824,20 @@ static int uvc_init_video_bulk(struct uvc_video_device *video,
         struct usb_host_endpoint *ep, gfp_t gfp_flags)
 {
         struct urb *urb;
-        unsigned int pipe, i;
-        __u16 psize;
-        __u32 size;
-
-        /* Compute the bulk URB size. Some devices set the maximum payload
-         * size to a value too high for memory-constrained devices. We must
-         * then transfer the payload accross multiple URBs. To be consistant
-         * with isochronous mode, allocate maximum UVC_MAX_ISO_PACKETS per bulk
-         * URB.
-         */
+        unsigned int npackets, pipe, i;
+        u16 psize;
+        u32 size;
+
         psize = le16_to_cpu(ep->desc.wMaxPacketSize) & 0x07ff;
         size = video->streaming->ctrl.dwMaxPayloadTransferSize;
         video->bulk.max_payload_size = size;
-        if (size > psize * UVC_MAX_ISO_PACKETS)
-                size = psize * UVC_MAX_ISO_PACKETS;
 
-        if (uvc_alloc_urb_buffers(video, size) < 0)
+        npackets = uvc_alloc_urb_buffers(video, size, psize, gfp_flags);
+        if (npackets == 0)
                 return -ENOMEM;
 
+        size = npackets * psize;
+
         if (usb_endpoint_dir_in(&ep->desc))
                 pipe = usb_rcvbulkpipe(video->dev->udev,
                                        ep->desc.bEndpointAddress);
diff --git a/drivers/media/video/uvc/uvcvideo.h b/drivers/media/video/uvc/uvcvideo.h
index 027947ea9b6e..b2639878f9b2 100644
--- a/drivers/media/video/uvc/uvcvideo.h
+++ b/drivers/media/video/uvc/uvcvideo.h
@@ -296,10 +296,8 @@ struct uvc_xu_control {
 
 /* Number of isochronous URBs. */
 #define UVC_URBS                5
-/* Maximum number of packets per isochronous URB. */
-#define UVC_MAX_ISO_PACKETS     40
-/* Maximum frame size in bytes, for sanity checking. */
-#define UVC_MAX_FRAME_SIZE      (16*1024*1024)
+/* Maximum number of packets per URB. */
+#define UVC_MAX_PACKETS         32
 /* Maximum number of video buffers. */
 #define UVC_MAX_VIDEO_BUFFERS   32
 /* Maximum status buffer size in bytes of interrupt URB. */