[PATCH v4 0/6] SimpleDRM Driver

David Herrmann dh.herrmann at gmail.com
Sun Sep 8 06:13:32 PDT 2013


On Sun, Sep 8, 2013 at 1:33 PM, Tom Gundersen <teg at jklm.no> wrote:
> Hi David,
> On Wed, Sep 4, 2013 at 7:34 PM, David Herrmann <dh.herrmann at gmail.com> wrote:
>> Hi
>> On Sun, Sep 1, 2013 at 3:36 PM, David Herrmann <dh.herrmann at gmail.com> wrote:
>>> Hi
>>> With the upcoming 3.12 merge-window, I thought people might find themselves with
>>> nothing to do, so here's a new SimpleDRM series. Comments welcome!
>>> This depends on the tip/x86/fb series in the x86-tip tree:
>>>   http://git.kernel.org/cgit/linux/kernel/git/tip/tip.git/log/?h=x86/fb
>>> Which, as far as I understood, will be pushed into 3.12 by the x86 people.
>> FYI, this is now merged in Linus' tree. See:
>> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=228abe73ad67665d71eacd6a8a347dd76b0115ae
>> So hopefully we can get SimpleDRM ready for 3.13.
> Now that simplefb works for me, I finally got around to testing this.
> Just a couple of comments:
>  * I guess you need to add the modalias "platform:simple-framebuffer"
> in addition to the "of:..." one to get module auto loading working.

Yes, sounds good.

>  * the driver currently doesn't work with your IORESOURCE_BUSY fix to
> sysfb (as might be expected(?)):
>         simple-framebuffer simple-framebuffer.0: cannot reserve VMEM
>         simple-framebuffer: probe of simple-framebuffer.0 failed with error -5

Yes, if the simple-framebuffer region is already marked BUSY,
simpleDRM must not (and doesn't have to) call __request_region() (or
request_mem_region()). I have to remove that call if the BUSY fix gets

> * except for that, fbcon on top of the fbdev fallback support works
> fine for me. I didn't yet try the drm driver itself, what clients (if
> any) are supposed to work with this, kmscon, weston?

Obviously, simpledrm doesn't support double-buffering, page-flipping
or other advanced techniques. So I currently doubt you can use any
real application on it as they all at least require 2 buffers. I
haven't decided whether to emulate these in the kernel driver or to
rely on user-space to deal with this reduced driver. It's quite likely
I will go with both. That means, a compatibility option that makes
simpledrm emulate any required techniques (multiple FBs,
page-flipping) but also user-space patches to maybe some day be able
to disable the kernel emulation.

Thanks a lot for testing all this. I will try to get the fixes into
rc2. The speed-improvements might have to wait for 3.13, though.


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