[linux-dvb] Re: AW: Re: [linuxtv-cvs] [CVS-LinuxTV] dvb-kernel

[Holger Waechtler <holger@convergence.de>]

Florian Schirmer wrote:
> Hi,
> 
> 
>>Sorry, I wasn't clear here: for 2.4.x I use the backported 2.5.x 
>>videodev-stuff.
>>
>>This is because we need v4l2, too, which is not available for 2.4.x at 
>>all. So, it we have video_copy() for all kernels in videodev.o, right?
> 
> 
> No. We're using the official v4l2 implementation for the 2.4.x kernel.
> (ftp://ftp.thedirks.org/pub/v4l2/kernel2.4/videodevX/videodevX-20020330.tgz)
> . This implementation doesn't provide vide_copy(). IMHO the dvb-core should
> not depend on v4l2. This will leed to a tricky situation (if the videodev
> isn't enabled): Either you deny enabling the dvb subsystem at all or will
> end up in UR symbols. I can't see any reason for that.

IIRC the video_usercopy() fake was implemented in a way that we use the 
generic_usercopy() implementation in case that either CONFIG_VIDEO_DEV 
is not defined or the kernel is too old and does not provides any 
video_usercopy() implementation.

This should work fine on any platform where we don't need the videodev 
interface at all (cards without MPEG decoder and without dependency to 
any v4l stuff, e.g. the Plaindigital PCMCIA cards) or on Settopboxes 
where the scaler interface has too many layers or is too sophisticated 
to match the v4l API.


> I know it is bad to have duplicated code in the kernel. But in the past
> situations like this were resolved this way. If enough users (subsystems)
> used (copied) the code, someone made a library for it. (eg. CRC32, zlib).

Alan was talking about a generic_usercopy() implementation a while ago 
but I suppose it never became reality. Is anybody of you willing to do 
it and post the related patch on the linux kernel mailing list?


> Conclusion: Keep the compat stuff but maybe rename it to dvb_copy or
> something else. IMHO. Comments?

generic_usercopy was the name, dvb_usercopy would be fine as well.

Holger



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