[PATCH 01/15] [media] Move mediabus format definition to a more standard place
hansverk at cisco.com
Tue Nov 4 03:09:59 PST 2014
Well, I gave two alternatives :-)
Both are fine as far as I am concerned, but it would be nice to hear
what others think.
On 11/04/14 11:45, Boris Brezillon wrote:
> Hi Hans,
> On Tue, 04 Nov 2014 11:20:40 +0100
> Hans Verkuil <hansverk at cisco.com> wrote:
>> Hi Boris,
>> On 11/04/14 10:54, Boris Brezillon wrote:
>>> Rename mediabus formats and move the enum into a separate header file so
>>> that it can be used by DRM/KMS subsystem without any reference to the V4L2
>>> Old V4L2_MBUS_FMT_ definitions are now referencing MEDIA_BUS_FMT_ value.
>> I missed earlier that v4l2-mediabus.h contained a struct as well, so it can't be
>> deprecated and neither can a #warning be added.
>> The best approach, I think, is to use a macro in media-bus-format.h
>> that will either define just the MEDIA_BUS value when compiled in the kernel, or
>> define both MEDIA_BUS and V4L2_MBUS values when compiled for userspace.
>> E.g. something like this:
>> #ifdef __KERNEL__
>> #define MEDIA_BUS_FMT_ENTRY(name, val) MEDIA_BUS_FMT_ # name = val
>> /* Keep V4L2_MBUS_FMT for backwards compatibility */
>> #define MEDIA_BUS_FMT_ENTRY(name, val) \
>> MEDIA_BUS_FMT_ # name = val, \
>> V4L2_MBUS_FMT_ # name = val
> Okay, but this means we keep adding V4L2_MBUS_FMT_ definitions even for
> new formats (which definitely doesn't encourage people to move on).
> Moreover, we add a V4L2 prefix in what was supposed to be a subsystem
> neutral header.
> Anyway, these are just nitpicks, and if you prefer this approach
> I'll rework my series :-).
>> An alternative approach is to have v4l2-mediabus.h include media-bus-format.h,
>> put #ifndef __KERNEL__ around the enum v4l2_mbus_pixelcode and add a big comment
>> there that applications should use the defines from media-bus-format.h and that
>> this enum is frozen (i.e. new values are only added to media-bus-format.h).
>> But I think I like the macro idea best.
> As you wish, my only intent is to use those bus format definitions in a
> DRM driver :-).
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