linux-kernel - Re: [PATCH v3] drm/gma500: depend on framebuffer

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Message-ID: <CADvTj4oms8R1fhFpyZ+juU=4Eozie6f-3fzz4+jtptj3M9VCbw@mail.gmail.com>
Date:   Thu, 21 Apr 2022 12:39:00 -0500
From:   James Hilliard <james.hilliard1@...il.com>
To:     Javier Martinez Canillas <javierm@...hat.com>
Cc:     Patrik Jakobsson <patrik.r.jakobsson@...il.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...ux.ie>,
        Randy Dunlap <rdunlap@...radead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH v3] drm/gma500: depend on framebuffer

On Thu, Apr 21, 2022 at 8:22 AM Javier Martinez Canillas
<javierm@...hat.com> wrote:
>
> On 4/21/22 14:54, Patrik Jakobsson wrote:
> > On Thu, Apr 21, 2022 at 2:47 PM Javier Martinez Canillas
> > <javierm@...hat.com> wrote:
>
> [snip]
>
> >>>>> diff --git a/drivers/gpu/drm/gma500/Kconfig b/drivers/gpu/drm/gma500/Kconfig
> >>>>> index 0cff20265f97..a422fa84d53b 100644
> >>>>> --- a/drivers/gpu/drm/gma500/Kconfig
> >>>>> +++ b/drivers/gpu/drm/gma500/Kconfig
> >>>>> @@ -2,11 +2,13 @@
> >>>>>   config DRM_GMA500
> >>>>>       tristate "Intel GMA500/600/3600/3650 KMS Framebuffer"
> >>>>>       depends on DRM && PCI && X86 && MMU
> >>>>> +     depends on FB
> >>>>
> >>>> Why do we need FB here? Framebuffer support should be hidden by DRM's
> >>>> fbdev helpers.
> >>>
> >>> It is not needed but gives him video output since it enables the drm
> >>> fbdev emulation.
> >>>
> >>
> >> I'm not sure to understand this. Shouldn't depend on DRM_FBDEV_EMULATION then?
> >
> > No, it shouldn't depend on any FBDEV stuff since it's not actually
> > required. It just happens to help in this case since weston + fbdev
> > backend works but not weston with drm backend (or whatever config
> > James have set).
>
> I see. Then the correct approach for them would be to just enable CONFIG_FB
> and DRM_FBDEV_EMULATION in their kernel config, rather than making this to
> depend on anything FB related as you said.

Yeah, so it looks like CONFIG_FB_EFI is not needed but
CONFIG_DRM_FBDEV_EMULATION is, I think I just assumed efifb
was what was needed based on the kernel logs.

This does not work:
CONFIG_FB enabled
CONFIG_DRM_FBDEV_EMULATION disabled

This works:
CONFIG_FB enabled
CONFIG_DRM_FBDEV_EMULATION enabled

>
> >
> >>
> >>> I looked some more at the logs and it seems weston doesn't work on his
> >>> system without the fbdev backend. So the question is why weston isn't
> >>> working without fbdev? Perhaps this is just a Weston configuration
> >>> issue?
> >>>
> >>
> >> But is weston using the fbdev emulated by DRM or the one registered by
> >> efifb? I thought that the latter from what was mentioned in this thread.
> >
> > It's using drm fbdev emulation with gma500 so EFIFB has nothing to do
> > with this. I believe it was just simply incorrectly reported. If I'm
> > correct then "depends on FB" is what makes video output work for
> > James.
> >
>
> Got it. Thanks for the clarification.

Here's my weston.ini:
[core]
shell=kiosk-shell.so
modules=systemd-notify.so
backend=drm-backend.so
idle-time=0
require-input=false
use-pixman=true

[shell]
locking=false
cursor-theme=Obsidian
panel-position=none

[output]
name=DVI-D-1
transform=rotate-270

[output]
name=DP-2
mode=off

[output]
name=LVDS-1
mode=off

[libinput]
touchscreen_calibrator=true

>
> --
> Best regards,
>
> Javier Martinez Canillas
> Linux Engineering
> Red Hat
>