Re: RFC: exposing controls in sysfs

[Mauro Carvalho Chehab <mchehab@redhat.com>]

Hans Verkuil wrote:
>> Hans Verkuil wrote:
>>> $ ls /sys/class/video4linux/video1/controls
>>> balance                           mpeg_insert_navigation_packets
>>> mpeg_video_aspect
>>> brightness                        mpeg_median_chroma_filter_maximum
>>> mpeg_video_b_frames
>>> chroma_agc                        mpeg_median_chroma_filter_minimum
>>> mpeg_video_bitrate
>>> chroma_gain                       mpeg_median_filter_type
>>> mpeg_video_bitrate_mode
>>> contrast                          mpeg_median_luma_filter_maximum
>>> mpeg_video_encoding
>>> hue                               mpeg_median_luma_filter_minimum
>>> mpeg_video_gop_closure
>>> mpeg_audio_crc                    mpeg_spatial_chroma_filter_type
>>> mpeg_video_gop_size
>>> mpeg_audio_emphasis               mpeg_spatial_filter
>>> mpeg_video_mute
>>> mpeg_audio_encoding               mpeg_spatial_filter_mode
>>> mpeg_video_mute_yuv
>>> mpeg_audio_layer_ii_bitrate       mpeg_spatial_luma_filter_type
>>> mpeg_video_peak_bitrate
>>> mpeg_audio_mute                   mpeg_stream_type
>>> mpeg_video_temporal_decimation
>>> mpeg_audio_sampling_frequency     mpeg_stream_vbi_format
>>> mute
>>> mpeg_audio_stereo_mode            mpeg_temporal_filter
>>> saturation
>>> mpeg_audio_stereo_mode_extension  mpeg_temporal_filter_mode
>>> volume
>>
>> It would be more intuitive if you group the classes with a few subdirs:
>>
>> /video/balance
>> /video/brightness
>> ...
>> /mpeg_audio/crc
>> /mpeg_audio/mute
>> ...
>> /audio/volume
>> /audio/bass
>> /audio/treble
> 
> 1) We don't have that information.
> 2) It would make a simple scheme suddenly a lot more complicated (see
> Andy's comments)
> 3) The main interface is always the application's GUI through ioctls, not
> sysfs.
> 4) Remember that ivtv has an unusually large number of controls. Most
> drivers will just have the usual audio and video controls, perhaps 10 at
> most.

Ok.

> I think we should just ditch this for the first implementation of the
> control framework. It can always be added later, but once added it is
> *much* harder to remove again. It's a nice proof-of-concept, though :-)

I like the concept, especially if we can get rid of other similar sysfs interfaces
that got added on a few drivers (pvrusb2 and some non-gspca drivers have
it, for sure). I think I saw some of the gspca patches also touching on sysfs.
Having this unified into a common interface is a bonus.

-- 

Cheers,
Mauro