[Buildroot] [PATCH v1 2/2] package/mesa3d: update vc4 help text

[Peter Seiderer]

Hello Yann,

On Tue, 4 Feb 2020 22:03:00 +0100, "Yann E. MORIN" <yann.morin.1998 at free.fr> wrote:

> Peter, All,
>
> On 2020-02-04 15:44 +0100, Peter Seiderer spake thusly:
> > Signed-off-by: Peter Seiderer <ps.report at gmx.net>
> > ---
> >  package/mesa3d/Config.in | 6 ++++--
> >  1 file changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/package/mesa3d/Config.in b/package/mesa3d/Config.in
> > index 1351d1cd97..9389a6132e 100644
> > --- a/package/mesa3d/Config.in
> > +++ b/package/mesa3d/Config.in
> > @@ -244,8 +244,10 @@ config BR2_PACKAGE_MESA3D_GALLIUM_DRIVER_VC4
> >  	select BR2_PACKAGE_LIBDRM_VC4
> >  	select BR2_PACKAGE_MESA3D_OPENGL_EGL
> >  	help
> > -	  Driver for Broadcom VC4 (rpi2/3) GPUs.
> > -	  It requires a vanilla 4.5+ kernel with drm vc4 (open) support.
> > +	  Driver for Broadcom VC4 (rpi2/3/4) GPUs (needs kmsro).
> > +	  It requires a recent enough mainline/raspberrypi kernel with
> > +	  drm vc4 (CONFIG_DRM_VC4) support enabled, for rpi4 additional
> > +	  v3d support is required.
>
> This is all very confusing...

I wanted to emphasize that no longer a vanilla/mainlain kernel is needed
as the official raspberry provided one gained the DRM VC4 support...

>
> First, you add rpi4 as supported by the vc4 driver, but the v3d driver

Not exactly supported, but needed for the rpi4 case...

> is also supposed to cover the rpi4. Are both needed? Is the v3d driver
> a supperset, a subset, a complement to vc4? If so, why doesn't the v3d
> driver select the vc4 driver (although it selects the vc4 drm backend)?

Because no one of the selecting BR2_PACKAGE_MESA3D_GALLIUM_KMSRO drivers
selects BR2_PACKAGE_MESA3D_GALLIUM_DRIVER_KMSRO...

> Or is it possible to use just the vc4 driver on rpi4?

For the RPi3 the vc4 (and kmsro) is sufficient, for the RPi4 all three
(v3d, vc4, kmsro) are needed...

Did not test if mesa3d-v3d compiles without libdrm vc4 (but checked it links
the same way against libdrm as mesa3d-vc4)...

>
> Then, you drop the 4.5+ version with this hazy "recent enough"
> categorisation. For the same reason as I explained in the previous
> patch, this is not nice.
>
> So, please explain in the commit log what is going on here...
>
> In the meantime, I marked the patch as rejected in patchwork.

Will try to come up with an better commit log...

Regards,
Peter

>
> Regards,
> Yann E. MORIN.
>
> >  config BR2_PACKAGE_MESA3D_GALLIUM_DRIVER_VIRGL
> >  	bool "Gallium virgl driver"
> > --
> > 2.25.0
> >
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