linux-kernel - Re: [PATH 0/4] [RFC] Support virtual DRM

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Date:   Wed, 23 Jun 2021 15:56:05 +0900
From:   Esaki Tomohito <etom@...l.co.jp>
To:     Pekka Paalanen <ppaalanen@...il.com>
Cc:     "Enrico Weigelt, metux IT consult" <lkml@...ux.net>,
        devicetree@...r.kernel.org, Takanari Hayama <taki@...l.co.jp>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        linux-doc@...r.kernel.org, David Airlie <airlied@...ux.ie>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        linux-renesas-soc@...r.kernel.org,
        Kieran Bingham <kieran.bingham+renesas@...asonboard.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Damian Hobson-Garcia <dhobsong@...l.co.jp>
Subject: Re: [PATH 0/4] [RFC] Support virtual DRM

Hi,
Thank you all for your comments.

On 2021/06/22 17:12, Pekka Paalanen wrote:
> On Tue, 22 Jun 2021 13:03:39 +0900
> Esaki Tomohito <etom@...l.co.jp> wrote:
> 
>> Hi, Enrico Weigelt
>> Thank you for reply.
>>
>> On 2021/06/22 1:05, Enrico Weigelt, metux IT consult wrote:
>>> On 21.06.21 08:27, Tomohito Esaki wrote:
>>>
>>> Hi,
>>>   
>>>> Virtual DRM splits the overlay planes of a display controller into multiple
>>>> virtual devices to allow each plane to be accessed by each process.
>>>>
>>>> This makes it possible to overlay images output from multiple processes on a
>>>> display. For example, one process displays the camera image without compositor
>>>> while another process overlays the UI.  
>>>
>>> Are you attempting to create an simple in-kernel compositor ?  
>>
>> I think the basic idea is the same as DRMlease.
> 
> Hi,
> 
> indeed. Why not use DRM leases instead?
> 

In this use case, I understand that this is not possible with DRM lease,
am I wrong?
I understand that it’s not possible to lease a plane and update planes
on the same output independently from different processes in current DRM
lease.

If this is correct, what do you think of adding support for plane leases
to the DRM lease to handle this case?

Thanks,
Tomohito Esaki