[Mesa-dev] [RFC] egl/android: Add DRM node probing and filtering

[Robert Foss]

On 04/20/2018 09:38 AM, Tomasz Figa wrote:
> On Fri, Apr 20, 2018 at 4:17 PM Robert Foss <robert.foss at collabora.com>
> wrote:
> 
> 
> 
>> On 04/20/2018 06:41 AM, Tomasz Figa wrote:
>>> Hi Rob,
>>>
>>> On Thu, Apr 19, 2018 at 1:03 AM Robert Foss <robert.foss at collabora.com>
>>> wrote:
>>>
>>>> This patch both adds support for probing & filtering DRM nodes
>>>> and switches away from using the GRALLOC_MODULE_PERFORM_GET_DRM_FD
>>>> gralloc call.
>>>
>>>> Currently the filtering is based just on the driver name,
>>>> and the desired name is supplied using the "drm.gpu.vendor_name"
>>>> Android property.
>>>
>>>> The filtering itself is done using the newly introduced
>>>> libdrm drmHandleMatch() call.
>>>
>>>> Signed-off-by: Robert Foss <robert.foss at collabora.com>
>>>> ---
>>>
>>>> This patch is based on[1], which contains a new libdrm function,
>>>> called drmHandleMatch(), which allows for matching an opened
>>>> drm node handle against some desired properties.
>>>
>>>> A choice that was made for this patch was to add support for
>>>> falling back to to DRM nodes that have failed the filtering,
>>>> if no node passes the filter.
>>>> If this wouldn't be useful to anyone, I would suggest ripping it
>>>> out since it is a little bit ugly&complex.
>>>
>>> This is actually not only useful, but quite of a requirement for Chrome
> OS,
>>> where we use the same Android image for devices with different GPU
> vendors.
>>> (Technically we could hack it up by injecting some per-board properties,
>>> but it would be painful from maintenance point of view.)
> 
>> Ack, I'll remove the fallback.
> 
> Sorry, I mean a fallback is needed. :) (+/- the missing driver check)

My mistake, I'll leave it in then!

> 
> 
>>>
>>> But actually, the way it is implemented in this patch will not work. The
>>> code assumes that the first DRM node that could be opened
>>> (loader_open_device()) is fine, but if you look at what we do in our
>>> Chromium patch [2], it is actually necessary to check if Mesa includes a
>>> driver for it (loader_get_driver_for_fd()).
>>>
>>> [2]
>>>
> https://chromium-review.googlesource.com/c/chromiumos/third_party/mesa/+/780797
> 
>> Ack, I'll add a check for a driver existing.
> 
> SGTM.
> 
> Best regards,
> Tomasz
>