linux-kernel - Re: [PATCH v1 3/3] drm/tegra: dc: Dedicate overlay plane to cursor on older Tegra's

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Date:   Sat, 17 Mar 2018 18:22:05 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Daniel Vetter <daniel@...ll.ch>,
        Thierry Reding <thierry.reding@...il.com>
Cc:     linux-tegra@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH v1 3/3] drm/tegra: dc: Dedicate overlay plane to cursor on
 older Tegra's

On 16.03.2018 10:36, Daniel Vetter wrote:
> On Thu, Mar 15, 2018 at 11:45 AM, Thierry Reding
> <thierry.reding@...il.com> wrote:
>> On Thu, Mar 15, 2018 at 04:00:25AM +0300, Dmitry Osipenko wrote:
>>> Older Tegra's do not support RGBA format for the cursor, but instead
>>> overlay plane could be used for it. Since there is no much use for the
>>> overlays on a regular desktop and HW-accelerated cursor is much better
>>> than a SW cursor, let's dedicate one overlay plane to the mouse cursor.
>>>
>>> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
>>> ---
>>>  drivers/gpu/drm/tegra/dc.c | 28 +++++++++++++++++++++++-----
>>>  1 file changed, 23 insertions(+), 5 deletions(-)
>>
>> Applied. I'm not entirely happy that we need to sacrifice one of the
>> overlay windows for this, but you're right, it's probably okay given
>> how little planes are used on a regular desktop.
>>
>> We could always provide a module parameter to switch this on and off
>> if that's ever something we want.
> 
> The idea with universal planes is that you can (at least try to) use
> the cursor overlay plane as a normal plane. It is only a hint to
> userspace, there's no requirement anywhere in atomic that you only use
> it as a cursor. That way desktops get a good hint for what the cursor
> plane should be, everyone else can still use all the planes.

Indeed, thank you for pointing at it. That is a nice feature.