[RFC 0/1] drm: Add Grain Media GM12U320 kms driver

[Marco Diego Aurélio Mesquita]

Hi Emil!

On Wed, Jun 7, 2017 at 7:30 AM, Emil Velikov <emil.l.velikov at gmail.com> wrote:
> On 2 June 2017 at 17:39, Marco Diego Aurélio Mesquita
> <marcodiegomesquita at gmail.com> wrote:
>> Hi Emil!
>>
>> On Fri, Jun 2, 2017 at 1:14 PM, Emil Velikov <emil.l.velikov at gmail.com> wrote:
>>> As Daniel mentioned in the earlier thread, factoring out things can be
>>> done as a follow-up.
>>> On the other hand, I _think_ that the blocker for this driver that
>>> it's not doing atomic mode setting.
>>>
>>
>> I've been looking on other small drivers to see how complicated would
>> it be to use the simple pipe framework. Both mxsfb and tinydrm do
>> atomic mode setting. It looks like some changes would be needed like
>> using the cma allocator and calling other specific functions tu do
>> atomic mode setting.
>>
>> Can you point to a simple patch that implements one of these "conversions"?
>
> TinyDRM is a helper/library which can be used to write a DRM driver
> driving 'simple' hardware.
> IIRC one of the ideas was to use it, as a reference you can skim
> through the latest driver [nor merged yet] that utilises the helper
> [1].

Thanks for helping!

I was indeed studying TinyDRM these days. But still haven't figured
out it was a lib. So I started modifying it to fit my needs and found
out it was too much work. Now I see, from the example you provided,
how simple it should be to use it. Thanks! I'll try to do the same for
gm12u320.

Anyway, for now I still have some problems. Mainly the way gm12u320
provides its modes. In the patch sent by Hans[2] the get_modes
function seems to be hardcoded. So, TinyDRM would probably need to be
modified so that a custom get_modes function can be provided. Do you
think that is reasonable? Noralf Tronnes, can you answer this?

Also, I've had some problems trying to compile TinyDRM. When I type
"make modules SUBDIRS=drivers/gpu/drm/tinydrm" I get lots of "WARNING
... undefined!" warnings. What is the right way to compile TinyDRM?

One more thing: isn't TinyDRM specific to spi devices?

> [1] https://lists.freedesktop.org/archives/dri-devel/2017-June/143357.html
[2] https://lists.freedesktop.org/archives/dri-devel/2017-June/143234.html