From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from perceval.ideasonboard.com ([95.142.166.194]:47719 "EHLO perceval.ideasonboard.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751226Ab3HTRda (ORCPT ); Tue, 20 Aug 2013 13:33:30 -0400 From: Laurent Pinchart To: Oliver Neukum Cc: linux-media@vger.kernel.org Subject: Re: [PATCH] uvc: more buffers Date: Tue, 20 Aug 2013 19:34:43 +0200 Message-ID: <12081572.xS4pFlgJZG@avalon> In-Reply-To: <1376298115.2689.13.camel@linux-fkkt.site> References: <1376053896-8931-1-git-send-email-oliver@neukum.org> <2017146.oxz2IcHa3F@avalon> <1376298115.2689.13.camel@linux-fkkt.site> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: linux-media-owner@vger.kernel.org List-ID: Hi Oliver, On Monday 12 August 2013 11:01:55 Oliver Neukum wrote: > On Fri, 2013-08-09 at 15:58 +0200, Laurent Pinchart wrote: > > > This is necessary to let the new generation of cameras from LiteOn used > > > in Haswell ULT notebook operate. Otherwise the images will be truncated. > > > > Could you please post the lsusb -v output for the device ? > > It is attached. No it isn't :-) > > Why does it need more buffers, is it a superspeed webcam ? > > No. It is HS. > > > > Signed-off-by: Oliver Neukum > > > --- > > > > > > drivers/media/usb/uvc/uvcvideo.h | 4 ++-- > > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > > > diff --git a/drivers/media/usb/uvc/uvcvideo.h > > > b/drivers/media/usb/uvc/uvcvideo.h index 9e35982..9f1930b 100644 > > > --- a/drivers/media/usb/uvc/uvcvideo.h > > > +++ b/drivers/media/usb/uvc/uvcvideo.h > > > @@ -114,9 +114,9 @@ > > > > > > /* Number of isochronous URBs. */ > > > #define UVC_URBS 5 > > > /* Maximum number of packets per URB. */ > > > > > > -#define UVC_MAX_PACKETS 32 > > > +#define UVC_MAX_PACKETS 128 > > > > That would mean up to 384KiB per URB. While not unreasonable, I'd like to > > know how much data your camera produces to require this. > > How to determine that? The UVC descriptors might provide some information. Do you get errors in the kernel log with UVC_MAX_PACKETS set to 32 ? > > > /* Maximum number of video buffers. */ > > > > > > -#define UVC_MAX_VIDEO_BUFFERS 32 > > > +#define UVC_MAX_VIDEO_BUFFERS 128 > > > > I don't think your camera really needs more than 32 V4L2 (full frame) > > buffers :-) > > Unfortunately, experimental evidence is that it does need them at > resolutions above 640x480 Could you please test it again with UVC_MAX_PACKETS set to 128 and UVC_MAX_VIDEO_BUFFERS set to 32 ? UVC_MAX_VIDEO_BUFFERS sets the maximum number of V4L2 full frame buffers, even 32 is probably way too high. -- Regards, Laurent Pinchart