linux-kernel - Re: [PATCH v2 0/4] drm/tiny: Add driver for Solomon SSD1307 OLED displays

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Date:   Wed, 9 Feb 2022 15:27:22 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Javier Martinez Canillas <javierm@...hat.com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Linux Fbdev development list <linux-fbdev@...r.kernel.org>,
        Linux PWM List <linux-pwm@...r.kernel.org>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Mark Brown <broonie@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        DRI Development <dri-devel@...ts.freedesktop.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Noralf Trønnes <noralf@...nnes.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Maxime Ripard <maxime@...no.tech>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>, Lee Jones <lee.jones@...aro.org>,
        Sam Ravnborg <sam@...nborg.org>
Subject: Re: [PATCH v2 0/4] drm/tiny: Add driver for Solomon SSD1307 OLED displays

Hi Andy,

On Wed, Feb 9, 2022 at 2:48 PM Andy Shevchenko
<andriy.shevchenko@...ux.intel.com> wrote:
> On Tue, Feb 08, 2022 at 04:10:49PM +0100, Javier Martinez Canillas wrote:
> > On 2/8/22 15:19, Geert Uytterhoeven wrote:
> > > On Fri, Feb 4, 2022 at 2:43 PM Javier Martinez Canillas
> > > <javierm@...hat.com> wrote:
> > >   - Kernel size increased by 349 KiB,
> > >   - The "Memory:" line reports 412 KiB less memory,
> > >   - On top of that, "free" shows ca. 92 KiB more memory in use after
> > >     bootup.
>
> The memory consumption should really be taken seriously, because these kind of
> displays are for embedded platforms with limited amount of resources.

Thanks for your concern!

Looking at the options that are auto-enabled, a few stand out that
look like they're not needed on systems witch such small displays,
or on legacy systems predating DDC:

    menuconfig DRM
            tristate "Direct Rendering Manager (XFree86 4.1.0 and
higher DRI support)"
            depends on (AGP || AGP=n) && !EMULATED_CMPXCHG && HAS_DMA
            select DRM_NOMODESET
            select DRM_PANEL_ORIENTATION_QUIRKS
            select HDMI

Not everyone pays HDMI royalties ;-)

            select FB_CMDLINE
            select I2C
            select I2C_ALGOBIT

I do need I2C, as it's the transport for my SSD1306 display, but not
everyone needs it.

            select DMA_SHARED_BUFFER
            select SYNC_FILE
    # gallium uses SYS_kcmp for os_same_file_description() to de-duplicate
    # device and dmabuf fd. Let's make sure that is available for our userspace.
            select KCMP

And:

    config DRM_BRIDGE
            def_bool y
            depends on DRM
            help
              Bridge registration and lookup framework.

    config DRM_PANEL_BRIDGE
            def_bool y


Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-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