On Wed, Feb 08, 2023 at 11:18:42AM +0200, Pekka Paalanen wrote: > On Fri, 3 Feb 2023 16:02:51 +0200 > Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> wrote: > > > On Fri, Feb 03, 2023 at 02:52:50PM +0100, Sebastian Wick wrote: > > > On Fri, Feb 3, 2023 at 2:35 PM Ville Syrjälä > > > <ville.syrjala@xxxxxxxxxxxxxxx> wrote: > > > > > > > > On Fri, Feb 03, 2023 at 01:59:07PM +0100, Sebastian Wick wrote: > > > > > On Fri, Feb 3, 2023 at 11:40 AM Ville Syrjälä > > > > > <ville.syrjala@xxxxxxxxxxxxxxx> wrote: > > > > > > > > > > > > On Fri, Feb 03, 2023 at 02:07:44AM +0000, Joshua Ashton wrote: > > > > > > > Userspace has no way of controlling or knowing the pixel encoding > > > > > > > currently, so there is no way for it to ever get the right values here. > > > > > > > > > > > > That applies to a lot of the other values as well (they are > > > > > > explicitly RGB or YCC). The idea was that this property sets the > > > > > > infoframe/MSA/SDP value exactly, and other properties should be > > > > > > added to for use userspace to control the pixel encoding/colorspace > > > > > > conversion(if desired, or userspace just makes sure to > > > > > > directly feed in correct kind of data). > > > > > > > > > > I'm all for getting userspace control over pixel encoding but even > > > > > then the kernel always knows which pixel encoding is selected and > > > > > which InfoFrame has to be sent. Is there a reason why userspace would > > > > > want to control the variant explicitly to the wrong value? > > > > > > > > What do you mean wrong value? Userspace sets it based on what > > > > kind of data it has generated (or asked the display hardware > > > > to generate if/when we get explicit control over that part). > > > > > > Wrong in the sense of sending the YCC variant when the pixel encoding > > > is RGB for example. > > > > > > Maybe I'm missing something here but my assumption is that the kernel > > > always has to know the pixel encoding anyway. The color pipeline also > > > assumes that the pixel values are RGB. User space might be able to > > > generate YCC content but for subsampling etc the pixel encoding still > > > has to be explicitly set. > > > > The kernel doesn't really know much atm. In theory you can just > > configure the thing to do a straight passthough and put anything you > > want into your pixels. > > But it's impossible to use a YCbCr framebuffer and have that *not* > converted to RGB for the KMS color pipeline even if userspace wanted it > to be strictly pass-through, only to be converted again to YCbCr for > the cable, is it not? > > Even more so with 4:2:0. > > How could it be possible to stop the driver from doing those two > YUV-to-RGB and RGB-to-YCbCr conversions at the beginning and at the end > of the KMS color pipeline? You can stop the conversion at the start of the pipeline by using a "RGB" framebuffer. At the end of the pipe it's not possible with the current props. -- Ville Syrjälä Intel
