Hi,

On Mon, Mar 05, 2018 at 03:21:26PM +0100, Maxime Ripard wrote:
> Here is an RFC at starting to test the plane formats using the
> Chamelium over the HDMI. This was tested using the vc4 DRM driver
> found on the RaspberryPi.
> 
> This is still pretty rough around the edges at this point, but I'd
> like to get feedback on a few issues before getting any further.
> 
>   * I've used pixman for now to convert back and forth the pattern and
>     the captured frame. While this worked quite well for the RGB
>     formats since pixman supports most (but not all) of them. However,
>     the long term plan is to also test YUV and more exotic (like
>     vendor specific) formats that pixman has 0 support for. So I
>     really wonder whether this is the right approach compared to:
>     - Using something else (but what?)?
>     - Rolling our own format conversion library?
> 
>   * I've so far had a single big test that will test all the formats
>     exposed by the planes that have a pixman representation. I wonder
>     whether this is preferrable, or if we want to have a subtest per
>     format. I guess the latter will be slightly better since we would
>     be able to catch regressions in the number of formats exposed that
>     we wouldn't be able to with the former.
> 
>   * Kind of related, I'm not sure what is the policy when it comes to
>     tests, and whether I should merge this tests with kms_chamelium or
>     leave it as a separate file.
> 
>   * One of the biggest challenge of the serie is to support formats
>     that have less bits than the reference frame. Indeed, the flow of
>     patterns is this one: the pattern will first be generated in
>     ARGB8888. It will then be converted to whatever format we want to
>     test, be fed into the display engine, that will output it, and the
>     Chamelium will capture it in ARGB8888.
>     However, when the plane format has less than 8 bits per color,
>     some upsampling will happen, where the less significant bits will
>     be filled with values that probably depend on the display
>     engine. Another side effect is that the CRC used in the Chamelium
>     tests cannot be used anymore.
>     The way I'm testing currently is that I'm retrieving the frame,
>     and then compare each pixels on their most significant bits. This
>     sounds inefficient, and it is, especially on the RPi that doesn't
>     have the best networking throughput out there.
>     I guess we could also generate a CRC for both an upsampling with
>     the lowest bits set to 1, and one for the lowest bits set to 0,
>     and try to see if one of them match. I guess this should cover
>     most of the situation.

Any comments on these points?
Maxime

-- 
Maxime Ripard, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com

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