Nouveau - Jul 2020 - Framebuffer double buffering (via FBIOPAN_DISPLAY)

Does NOUVEAU support mmaping a double-sized Framebuffer?
When attempting to run, where fd refers to "/dev/fb0":

mmap(ptr, screensize * 2, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);

I get back an invalid argument error.  This doesn't happen if I only
request a single screensize.  Is this a limitation of the driver?

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Are you setting the overallocation to 200?

On Sun, Jul 5, 2020 at 3:41 AM Michael T. Kloos
<michael at michaelkloos.com> wrote:
>
> Does NOUVEAU support mmaping a double-sized Framebuffer?
> When attempting to run, where fd refers to "/dev/fb0":
>
> mmap(ptr, screensize * 2, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
>
> I get back an invalid argument error.  This doesn't happen if I only
> request a single screensize.  Is this a limitation of the driver?
>
> _______________________________________________
> Nouveau mailing list
> Nouveau at lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/nouveau

<div dir='auto'>I am not familiar with that setting, but I have
really struggled to find documentation on dealing with the framebuffer. 
Referring to this guide,
"http://betteros.org/tut/graphics1.php#doublebuffer", I attempted to
set the mmap allocation size to double, but it caused the mmap to fail.  I no
longer believe that it is a driver issue, though, because I just tried it again
on a dell laptop with Intel HD Graphics 4400 to the same
failure.</div><div class="gmail_extra"><br><div
class="gmail_quote">On Jul 5, 2020 12:35, Ilia Mirkin
<imirkin@alum.mit.edu> wrote:<br type="attribution"
/><blockquote class="quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex"><p
dir="ltr">Are you setting the overallocation to 200?
<br>

<br>
On Sun, Jul 5, 2020 at 3:41 AM Michael T. Kloos
<br>
<michael@michaelkloos.com> wrote:
<br>
>
<br>
> Does NOUVEAU support mmaping a double-sized Framebuffer?
<br>
> When attempting to run, where fd refers to "/dev/fb0":
<br>
>
<br>
> mmap(ptr, screensize * 2, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
<br>
>
<br>
> I get back an invalid argument error.  This doesn't happen if I only
<br>
> request a single screensize.  Is this a limitation of the driver?
<br>
>
<br>
> _______________________________________________
<br>
> Nouveau mailing list
<br>
> Nouveau@lists.freedesktop.org
<br>
> https://lists.freedesktop.org/mailman/listinfo/nouveau
<br>
</p>
</blockquote></div><br></div>