DRM Client Capability for aspect ratio

"Nautiyal, Ankit K" <ankit.k.nautiyal@xxxxxxxxx> · Tue, 17 Oct 2017 15:25:47 +0530



    Hi All,
    
    
    I
          am working for adding the
          DRM Client cap for the aspect ratio support as part of the
          series: 
    
    
    https://patchwork.freedesktop.org/series/10850/
          : Picture aspect ratio support in DRM layer by
          Shashank Sharma.
    
    
    I
          have an open as to how to go
          about it.
    
    
    I
          was going through the existing
          DRM Client Cap like DRM_CLIENT_CAP_STEREO_3D,
          DRM_CLIENT_CAP_ATOMIC.
    
    
    On
          Similar lines, I was able
          to add the new DRM_CLIENT_CAP_ASPECT_RATIO. I also added a
          member 'aspect_ratio_required' in drm_file structure,
    
    
    which
          is set, when the client
          calls drm_setclientcap( ), for aspect ratio, just like its
          being done for other
          DRM Client Caps. 
    
    
    Now
          what I want to do is 
    
    
    1.     Setting
          the aspect-ratio flag-bits (19-22) in drmModeModeInfo only
            if the client
          advertises that it requires the aspect-ratio.
    
    
    So I
          need to have this information (that client requires aspect
          ratio) available in
          the function:
    
    
    drm_mode_convert_to_umode(
            ) : Where the
            flag bits are actually set
    
    
    2.     Similarly
          in case of modeset request from the client, we would want to
          parse the aspect
          ratio bits from the requested 
          drmModeModeInfo
          only if the client requires aspect ratio. 
    
    
    This will require change in the function:
    
    
    drm_mode_convert_umode()  : Where the flag bits of 
            drm_mode_mode_info are read by the drm layer to determine
            the aspect ratio and set in drm_display_mode)
    
    
    The
          problem is that, both
          these functions have drm_mode_mode_info and drm_display_mode
          as the only arguments, but
          our flag aspect_ratio_required is in file_priv (struct
          drm_file).
    
    
    To
          do this there are two ways
          I can think of:
    
    
    1.    
            Change the
          drm_mode_convert_umode() to include
          aspect_ratio_required flag.
            Before
          calling this function, the
          file_priv->aspect_ratio_required will be checked and the
          flag will be set
          accordingly.
    

    2.    
            While
          getting the drmClientCap from client, instead of storing
          this information in file-priv, store this info in some other
          structure.
    
    
    Is my
          understanding correct or is there any other way I should
          handle the drm client cap?
    

    Thanks and Regards,
    Ankit

        
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