Hi Pavel, Thank you for the patch. On Monday, 4 September 2017 11:14:17 EEST Pavel Rojtberg wrote: > From: Pavel Rojtberg <rojtberg@xxxxxxxxx> > > attaching two Logitech C615 webcams currently results in > VIDIOC_STREAMON: No space left on device > as the required bandwidth is not estimated correctly by the device. > In fact it always requests 3060 bytes - no matter the format or resolution. > > setting UVC_QUIRK_FIX_BANDWIDTH does not help either as it is only > implemented for uncompressed streams. > > This patch extends UVC_QUIRK_FIX_BANDWIDTH to MJPEG streams by making a > (conservative) assumption of 4bpp for MJPEG streams. > As the actual compression ration is often closer to 1bpp this can be > overridden via the new mjpeg_bpp parameter. > > Based on: > https://www.mail-archive.com/linux-uvc-devel@xxxxxxxxxxxxxxxx/msg05724.html > --- > drivers/media/usb/uvc/uvc_driver.c | 14 +++++++++++++- > drivers/media/usb/uvc/uvc_video.c | 3 ++- > 2 files changed, 15 insertions(+), 2 deletions(-) > > diff --git a/drivers/media/usb/uvc/uvc_driver.c > b/drivers/media/usb/uvc/uvc_driver.c index 70842c5..f7b759e 100644 > --- a/drivers/media/usb/uvc/uvc_driver.c > +++ b/drivers/media/usb/uvc/uvc_driver.c > @@ -37,6 +37,7 @@ unsigned int uvc_no_drop_param; > static unsigned int uvc_quirks_param = -1; > unsigned int uvc_trace_param; > unsigned int uvc_timeout_param = UVC_CTRL_STREAMING_TIMEOUT; > +static unsigned int uvc_mjpeg_bpp_param; > > /* ------------------------------------------------------------------------ > * Video formats > @@ -463,7 +464,16 @@ static int uvc_parse_format(struct uvc_device *dev, > strlcpy(format->name, "MJPEG", sizeof format->name); > format->fcc = V4L2_PIX_FMT_MJPEG; > format->flags = UVC_FMT_FLAG_COMPRESSED; > - format->bpp = 0; > + if ((uvc_mjpeg_bpp_param >= 1) && (uvc_mjpeg_bpp_param <= 16)) { > + format->bpp = uvc_mjpeg_bpp_param; > + } else { > + /* conservative estimate. Actual values are around 1bpp. > + * see e.g. > + * https://developers.google.com/speed/webp/docs/webp_study > + */ > + format->bpp = 4; > + } > + > ftype = UVC_VS_FRAME_MJPEG; > break; > > @@ -2274,6 +2284,8 @@ module_param_named(trace, uvc_trace_param, uint, > S_IRUGO|S_IWUSR); MODULE_PARM_DESC(trace, "Trace level bitmask"); > module_param_named(timeout, uvc_timeout_param, uint, S_IRUGO|S_IWUSR); > MODULE_PARM_DESC(timeout, "Streaming control requests timeout"); > +module_param_named(mjpeg_bpp, uvc_mjpeg_bpp_param, uint, S_IRUGO|S_IWUSR); > +MODULE_PARM_DESC(mjpeg_bpp, "MJPEG bits per pixel for bandwidth quirk"); I'd rather avoid adding a new module parameter for this, it would be confusing for users. What is your use case to make the MJPEG average BPP configurable ? Can't we come up with a heuristic that would calculate it automatically ? > /* ------------------------------------------------------------------------ > * Driver initialization and cleanup > diff --git a/drivers/media/usb/uvc/uvc_video.c > b/drivers/media/usb/uvc/uvc_video.c index fb86d6a..382a0be 100644 > --- a/drivers/media/usb/uvc/uvc_video.c > +++ b/drivers/media/usb/uvc/uvc_video.c > @@ -127,7 +127,8 @@ static void uvc_fixup_video_ctrl(struct uvc_streaming > *stream, if ((ctrl->dwMaxPayloadTransferSize & 0xffff0000) == 0xffff0000) > ctrl->dwMaxPayloadTransferSize &= ~0xffff0000; > > - if (!(format->flags & UVC_FMT_FLAG_COMPRESSED) && > + if ((!(format->flags & UVC_FMT_FLAG_COMPRESSED) || > + (format->fcc == V4L2_PIX_FMT_MJPEG)) && > stream->dev->quirks & UVC_QUIRK_FIX_BANDWIDTH && > stream->intf->num_altsetting > 1) { > u32 interval; -- Regards, Laurent Pinchart
