[PATCH 30/30] fbdev: Make support for userspace interfaces configurable

[Geert Uytterhoeven]

Hi Javier,

On Fri, Jun 9, 2023 at 11:59 AM Javier Martinez Canillas
<javierm at redhat.com> wrote:
> Thomas Zimmermann <tzimmermann at suse.de> writes:
> >>> I'd also question the argument that there's even fbdev userspace out
> >>> there. It was never popular in it's heyday and definitely hasn't
> >>> improved since then. Even the 3 people who still ask for fbdev support
> >>
> >> There's X.org, DirectFB, SDL, ...
> >
> > None of these examples has a dependency on fbdev. They can freely switch
> > backends and have moved to DRM. Anything program utilizing these
> > examples has no dependency on fbdev either.
> >
> > When I say "userspace" in this context, it's the one old program that
> > supports nothing but fbdev. TBH I'm having problems to come up with
> > examples.
> >
>
> I personally have two real world examples that can give to you :)
>
> 1) I've a IoT device at home that has a bunch of sensors (temperatury,
>    humidity, etc) and a SSD1306 display panel to report that. It just
>    has small fbdev program to print that info. I could probably port
>    to KMS but didn't feel like it. Found a fbdev program that I could
>    modify and got the job done.
>
> 2) I built a portable retro console for my kids, that uses a ST7735R
>    LCD panel. The software I use is https://www.retroarch.com/ which
>    uses fbdev by default (I believe that supports a KMS mode but out
>    of the box it works with fbdev and that's better tested by them.
>
> So even when I'm not interested and don't want to enable any of the
> fbdev drivers, I want to use the ssd130x and st7735r DRM drivers and
> the DRM fbdev emulation layer.
>
> In other words, there's real use cases for supporting fbdev programs
> with DRM drivers. Now, I agree with this patch-set and probably will
> disable the user-space fbdev interface in Fedora, but on my embedded
> projects I will probably keep it enabled.
>
> That's why I think that we should support the following combinations:
>
> * fbdev drivers + DRM fbdev emulation + fbdev user-space

"fbdev drivers + fbdev user-space", I assume?

> * only DRM drivers without fbdev emulation nor fbdev user-space (your series)

Thomas' series includes fbdev emulation here, for the text console.

> * only DRM fbdev emulation + fbdev user-space enabled (FB_CORE)

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds