[Nouveau] Selecting supported chipsets in the driver?

[Ilia Mirkin]

On Wed, Jul 31, 2013 at 10:44 AM, Martin Peres <martin.peres at free.fr> wrote:
> On 30/07/2013 18:43, Ilia Mirkin wrote:
>>
>> On Tue, Jul 30, 2013 at 6:31 PM, Emil Velikov <emil.l.velikov at gmail.com>
>> wrote:
>>>
>>> On 30/07/13 21:39, Christ-Jan Wijtmans wrote:
>>>>
>>>> Hi, my apologies if this is the wrong place to post this.
>>>> I had the desire to turn on or off support for certain chipsets.
>>>> Because i felt like the nouveau drivers are (relatively) quite large and
>>>> depends on some kernel code that would only be used for certain
>>>> chipsets.
>>>> I will take some time this week to see how this is coded and if its
>>>> possible but i just wanted a head sup opinion on you guys before i start
>>>> wasting my time.
>>>>
>>> I'm not entirely sure if you're talking about the kernel module, ddx
>>> (xf86-video-nouveau) or mesa.
>>>
>>> In either case, all three should be relatively easy to do, as normally
>>> the generation specific code is divided. Not too sure if it's worth the
>>> effort though
>>>
>>> * kernel module - 1.7 MiB, ~400KiB gzip
>>> * ddx - ~200KiB
>>> * mesa - 6.3 MiB (nouveau/gallium only)
>>>
>>> As you can see the sizes are not that big, and I'm not sure if the
>>> maintainers would be up-to the idea
>>>
>>> Not a maintainer myself so take the last statement if a healthy pinch of
>>> salt :)
>>
>> I'm not a maintainer either, but to provide an opposing opinion, I
>> strongly support the notion of being able to select card generations
>> to build support for. 1.7M of kernel code is huge. I don't even think
>> it'd be that hard (at least for the kernel module and mesa, and I
>> think there's a lot less value in doing it for the DDX). I think it
>> might be as easy as some Makefile changes + a couple of ifdefs in the
>> init code to do Y/N selects. Making it so that the additional
>> functionality can be loaded on demand (i.e. Y/M/N) may be much
>> trickier, to the point of it not being worth it for the additional
>> complexity.
>>
>>    -ilia
>
>
> In mesa, it is possible to build the driver you want (nouveau_vieux, nv30,
> nv50 or nvc0) so the feature is already there.

Really? How do you compile only nv50? (Hint: you can't. nv30/nv50/nvc0
are all linked together in the nouveau driver, no way to split them
out, largely because of the nouveau_drm_screen_create function.)

> There is no point for the ddx.
>
> As for drm, I sure would use this feature as this would cut down compilation
> time a lot when doing out of the tree builds. With the core arch, in theory,
> it shouldn't be that hard if you want plan on using old cards only. However,
> if you plan on doing the opposite (drop old cards support), it is harder
> as newer cards still use code written for the old ones. If you like,
> you can draw a dependency map quite easily by looking into the device
> directory that will contain all the dependencies for every chipset.
>
> One more thing, maintaining these dependencies will be done poorly and
> eat development time. So I'm not in huge favour of this unless you
> introduce a system that only compiles code for chipsets up to a certain
> point (which is useless IMO).
>
>
>
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