Re: drm/msm/mdp5: undefined CONFIG_MSM_BUS_SCALING

From: Rob Clark
Date: Thu Apr 09 2015 - 10:51:07 EST

On Thu, Apr 9, 2015 at 10:20 AM, Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
> On Thu, Apr 09, 2015 at 09:49:58AM -0400, Rob Clark wrote:
>> On Thu, Apr 9, 2015 at 7:22 AM, Valentin Rothberg
>> <valentinrothberg@xxxxxxxxx> wrote:
>> > Hi Hai,
>> >
>> > your commit d5af49c92a8a ("drm/msm/mdp5: Enable DSI connector in msm drm
>> > driver") in today's Linux next tree adds an #ifdef with CONFIG_MSM_BUS_SCALING
>> > as condition. MSM_BUS_SCALING is not defined in Kconfig, so the code in this
>> > #ifdef block won't be compiled at its current state.
>> >
>> > I saw some references on this Kconfig option in other files; is there a
>> > reason for the absence of MSM_BUS_SCALING?
>> right now, it is something that only exists in downstream kernels (for
>> example, android device kernels).. but in those kernels it is
>> mandatory to use, as by default the memory/bus is downclocked and the
>> display would underflow if we did not request sufficient bandwidth.
>> It only exists right now in the upstream kernel to simplify
>> backporting to various device kernels
> That's crazy. You are asking upstream to maintain code in order to just
> make out of tree crap easier to maintain, which you don't have any plan
> to ever upstream? That causes havoc on static analysis tools and
> prevents anyone from ever being able to even change the code for new api
> changes and test build it.

Hey, don't blame me for the downstream kernels. But at various points
in time I've had to backport drm/msm to various device kernels in
order to work on the userspace/mesa end of things. (And, well, there
are other crazy folks out there who want to get open source graphics
drivers working on various phones/tablets.) It was a choice to make
my life easier. You know, because reverse engineering a gpu is a walk
in the park..


> If this was in a subsystem that I maintain, I'd delete it tomorrow. But
> in the end, it's up to David to decide if he wants to waste the cycles
> or not.
> Ick ick ick.
> greg k-h
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