Messages in this thread | | | Date | Thu, 15 May 2008 08:34:42 -0700 | From | Dean Anderson <> | Subject | Re: [v4l-dvb-maintainer] [PATCH] USB: add Sensoray 2255 v4l driver |
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Trent Piepho wrote: > On Wed, 14 May 2008, Greg KH wrote: > >> On Thu, May 15, 2008 at 03:17:42AM +0200, Markus Rechberger wrote: >> >>> Hi Dean, Greg, >>> >> Adding dean to the cc: line... :) >> >>> On 5/14/08, Greg KH <greg@kroah.com> wrote: >>> >>>> From: Dean Anderson <dean@sensoray.com> >>>> >>>> >> <big patch snipped> >> >> >>> Why do you do those conversions in kernelspace? >>> ffmpeg/libswscale has optimized code for colourspace conversions. >>> I know a few drivers do that in kernelspace but it's way more flexible >>> in userspace and depending on the optimization requires less CPU >>> power. >>> >> I thought they were there as needed by some V4L1 applications, but that >> code was recently removed by Dean I think. If they don't need to be >> there, and userspace apps can properly handle the different colorspace, >> then I'll be glad to remove them. >> > > Virtually all apps (V4L1 & 2) can handle YUV and RGB colorspaces. > Certainly all the major ones do and all the major libraries as well. > > The problem is when the device only supports some vendor specific or > otherwise very uncommon format. In that case not doing the conversion in > the kernel means the device won't work with any existing software without > patches. In this case, while it's not "the right way", drivers often end > up including an in kernel conversion for pragmatic reasons. > > This was a problem with the bayer format, but now userspace support for > that format is more common. >
I agree the conversions don't belong in a driver. For the record, the following are done in the 2255 hardware: V4L2_PIX_FMT_GREY and V4L2_PIX_FMT_YUV422P.
Since planar YUV formats such as V4L2_PIX_FMT_YUV422P are still not that well supported, is it possible to keep at least one packed YUV format(V4L2_PIX_FMT_YUYV) in the driver? If not, let me know. I will strongly suggest that the hardware Engineers add YUY2 or YUYV on board in the DSP firmware. Thanks, Dean
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