Hi Takashi, (CC'ing Greg and the linux-usb mailing list) Thank you for the patch. On Thu, Jun 09, 2022 at 10:22:46AM +0200, Takashi Iwai wrote: > As default, the DMA max segment size is set to 64k, and uvcvideo may > overflow that size easily, resulting in a warning like: > > DMA-API: xhci_hcd 0000:00:14.0: mapping sg segment longer than device claims to support [len=98304] [max=65536] > > Explicitly set up the DMA max segment size for avoiding spurious kernel > warnings. > > Signed-off-by: Takashi Iwai <tiwai@xxxxxxx> > --- > drivers/media/usb/uvc/uvc_video.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c > index 1b4cc934109e..25aa6e6a6906 100644 > --- a/drivers/media/usb/uvc/uvc_video.c > +++ b/drivers/media/usb/uvc/uvc_video.c > @@ -2160,6 +2160,8 @@ int uvc_video_init(struct uvc_streaming *stream) > for_each_uvc_urb(uvc_urb, stream) > INIT_WORK(&uvc_urb->work, uvc_video_copy_data_work); > > + dma_set_max_seg_size(uvc_stream_to_dmadev(stream), UINT_MAX); > + uvc_stream_to_dmadev() returns the pointer to the HCD's struct device, which is shared between all drivers on the bus. Is it really fine for a USB device driver to change the maximum segment size of the HCD device directly ? > return 0; > } > -- Regards, Laurent Pinchart
