Re: [PATCH 00/28] OpenChrome DRM for Linux 5.20

[Javier Martinez Canillas <javierm@redhat.com>]

Hello,

On 6/28/22 14:21, Thomas Zimmermann wrote:
> Hi
> 
> Am 27.06.22 um 23:32 schrieb Sam Ravnborg:
>> Hi Kevin/Thomas,
>>
>>>
>>> I had a brief look over the patches. Even though the code looks fairly rough
>>> in places, I think we should get this driver merged ASAP.
>>
>> Agreed, we have a had a few cases where we dragged out committing much
>> too long time.
>>
>> Timing wise, it would be good if we can already hit drm-misc-next right
>> _after_ the pull -so we have a full cycle to fix anything before it hits
>> mainline.
>>
>>> For the old via driver, I think we need a better apprach. IMHO it would be
>>> preferable to put the new driver into via/ but keep the old driver there as
>>> well.  A build option would control which is being used.
>>
>> I assume the user base for via drivers are very small and they have the
>> fbdev driver already.
>> So I support replacing the current via drm driver as Kevin tries to do.
> 
> I don't know if there are still users of the old userspace, but if so I 
> would consider this removal a regression. I think the old code supports 
> 3d and video decoding. Depending on the feature set, 3d support might 
> not be useful any longer, but video decoding probably is.  (I might be 
> wrong about all this.) IMHO we should not simply remove this at least 
> until we can verify that it's no longer useful to anyone.
>

I strongly agree with Thomas on this.
 
> However, legacy support is trivial. Kevin, please see the attached files 
> for two cleanup patches. You're welcome to add them to the start of your 
> patchset to get the legacy code out of the way.
>

I'm not sure about this approach, I think that having completely separated
drivers would be better to maintain in the long run since it's likely that
the legacy VIA driver will only get bug fixes (if any) and could be removed
once the new modsetting driver has feature parity, the legacy can be dropped.
 
Maybe an alternative could be to add a drivers/gpu/drm/legacy directory and
move all the legacy DRM drivers there ? And the Kconfig symbol could be i.e:
CONFIG_DRM_LEGACY_VIA and same for the others legacy DRM drivers.

And the directory could only be sourced from Kconfig when CONFIG_DRM_LEGACY
is enabled and make it default to n. If in a few of releases nobody complains
then the whole directory could be removed.

-- 
Best regards,

Javier Martinez Canillas
Linux Engineering
Red Hat