Re: [Linux-fbdev-devel] drm_fb_helper: Impossible to change video mode

[Alex Deucher <alexdeucher@gmail.com>]

2010/3/11 Michel Dänzer <michel@daenzer.net>:
> On Wed, 2010-03-10 at 13:10 -0500, Alex Deucher wrote:
>> On Wed, Mar 10, 2010 at 1:05 PM, Alex Deucher <alexdeucher@gmail.com> wrote:
>> > On Wed, Mar 10, 2010 at 12:42 PM, James Simmons <jsimmons@infradead.org> wrote:
>> >>
>> >> See my other post about what fbdev really means in its historical
>> >> context. The struct fb_info really maps better to drm_crtc than to
>> >> drm_framebuffer. In fact take the case of the matrox fbdev driver. It
>> >> creates two framebuffer devices even tho it used one static framebuffer.
>> >> What the driver does is splits the framebuffer in two and assigned each
>> >> part to a CRTC.
>> >
>> > The only problem with that is that it eats a lot of memory for the
>> > console which limits X when it starts. On cards with limited vram ,
>> > you might not have enough memory left for any meaningful acceleration
>> > when X starts.
>>
>> It would be nice to find a way to reclaim the console memory for X,
>> but I'm not sure that can be done and still provide a good way to
>> provide oops support.
>
> What do you think the average user will care about more?
>
>      * Seeing kernel oops/panic output about once in a lifetime.
>      * Being able to start/use X in the first place and enabling it to
>        use all of VRAM.
>
> Personally, I've never even seen any kernel oops/panic output despite
> numerous opportunities for that in the couple of months I've been using
> KMS. But I have spent considerable time and effort trying to get rid of
> the pinned fbcon BO. If the oops/panic output is the only thing
> preventing that, maybe that should only be enabled via some module
> option for developers.

I'm all for it!

Alex

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