[PATCH 3/4] drm/fb-helper: Add module option to disable fbdev emulation

Archit Taneja architt at codeaurora.org
Wed Aug 26 05:29:14 PDT 2015

On 08/26/2015 05:07 PM, Daniel Vetter wrote:
> On Wed, Aug 26, 2015 at 01:34:58PM +0200, Daniel Vetter wrote:
>> On Wed, Aug 26, 2015 at 02:14:37PM +0530, Archit Taneja wrote:
>>> On 08/26/2015 10:42 AM, Archit Taneja wrote:
>>>> On 08/25/2015 07:15 PM, Daniel Vetter wrote:
>>>>> Faster than recompiling.
>>>>> Note that restore_fbdev_mode_unlocked is a bit special and the only
>>>>> one which returns an error code when fbdev isn't there - i915 needs
>>>>> that one to not fall over with some additional fbcon related restore
>>>>> code. Everyone else just ignores the return value or only prints a
>>>>> DRM_DEBUG level message.
>>>> Reviewed-by:Archit Taneja <architt at codeaurora.org>
>>> With the module param, and the drivers should see the following state(
>>> based on the truth table below):
>>> module param | config option
>>>     true      |    true       -> real helper funcs called, driver
>>>                                  allocated drm_fb_helper is correctly
>>>                                  populated.
>>>     false     |    true       -> real helper funcs called, but bailed
>>>                                  out early, driver allocated
>>>                                  drm_fb_helper is non-NULL, but we won't
>>>                                  end up using it.
>> Hm I tried to give drivers the same semantics here as with the stub
>> functions. Where did I screw up? The goal really was to match the end
>> result for drivers ...
> Note that at least for i915 we can't make it perfectly equal since i915
> compiles out a few more things with FBDEV_EMULATION=n than just the stubs.
> Long-term we might want to push some of that into helpers too perhaps.

Ah, I missed looking at this mail.

Yeah, that's what I wanted to mainly point out. It looks okay

Since the param is 'true' by default. Things should be okay for all
drivers. If someone reports an issue with a driver with the above
combination, we could fix it individually.

I guess the next step now is to remove the custom config fbdev
emulation options and module params from drivers that have

After that, we could start with scary process of removing the
CONFIG_FB and CONFIG_DRM_KMS_FB_HELPER from each driver.


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