linux-kernel - Re: [PATCH 0/6] Refactor the vkms to accept new formats

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Date:   Mon, 18 Oct 2021 10:53:33 +0300
From:   Pekka Paalanen <ppaalanen@...il.com>
To:     Igor Matheus Andrade Torrente <igormtorrente@...il.com>
Cc:     rodrigosiqueiramelo@...il.com, melissa.srw@...il.com,
        hamohammed.sa@...il.com, daniel@...ll.ch, airlied@...ux.ie,
        contact@...rsion.fr, leandro.ribeiro@...labora.com,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        lkcamp@...ts.libreplanetbr.org
Subject: Re: [PATCH 0/6] Refactor the vkms to accept new formats

On Tue,  5 Oct 2021 17:16:31 -0300
Igor Matheus Andrade Torrente <igormtorrente@...il.com> wrote:

> XRGB to ARGB behavior
> =================
> During the development, I decided to always fill the alpha channel of
> the output pixel whenever the conversion from a format without an alpha
> channel to ARGB16161616 is necessary. Therefore, I ignore the value
> received from the XRGB and overwrite the value with 0xFFFF.
> 
> My question is, is this behavior acceptable?

Hi,

that is the expected behaviour. X channel values must never affect
anything on screen, hence they must never affect other channels'
values. You are free to completely ignore X channel values, and if your
output buffer has X channel, then you are free to write (or not write,
unless for security reasons) whatever into it.


Thanks,
pq

> 
> [1] https://lists.freedesktop.org/archives/igt-dev/2021-October/036125.html
> 
> Igor Matheus Andrade Torrente (6):
>   drm: vkms: Replace the deprecated drm_mode_config_init
>   drm: vkms: Alloc the compose frame using vzalloc
>   drm: vkms: Replace hardcoded value of `vkms_composer.map` to
>     DRM_FORMAT_MAX_PLANES
>   drm: vkms: Add fb information to `vkms_writeback_job`
>   drm: vkms: Prepare `vkms_wb_encoder_atomic_check` to accept multiple
>     formats
>   drm: vkms: Refactor the plane composer to accept new formats
> 
>  drivers/gpu/drm/vkms/vkms_composer.c  | 275 ++++++++++++++------------
>  drivers/gpu/drm/vkms/vkms_drv.c       |   5 +-
>  drivers/gpu/drm/vkms/vkms_drv.h       |  12 +-
>  drivers/gpu/drm/vkms/vkms_formats.h   | 125 ++++++++++++
>  drivers/gpu/drm/vkms/vkms_writeback.c |  27 ++-
>  5 files changed, 304 insertions(+), 140 deletions(-)
>  create mode 100644 drivers/gpu/drm/vkms/vkms_formats.h
> 


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