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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAMuHMdWvrJip+W6ZZoO2ZURLc5CYmFno3=Sa2mL4xJE8gMzFqg@mail.gmail.com>
Date:   Tue, 8 Feb 2022 16:23:29 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Javier Martinez Canillas <javierm@...hat.com>
Cc:     "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>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Sam Ravnborg <sam@...nborg.org>
Subject: Re: [PATCH v2 0/4] drm/tiny: Add driver for Solomon SSD1307 OLED displays

Hi Javier,

On Tue, Feb 8, 2022 at 4:10 PM Javier Martinez Canillas
<javierm@...hat.com> 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:
> >> This patch series adds a DRM driver for the Solomon OLED SSD1305, SSD1306,
> >> SSD1307 and SSD1309 displays. It is a port of the ssd1307fb fbdev driver.
> >
> > I gave it a try on an Adafruit FeatherWing 128x32 OLED, connected to an
> > OrangeCrab ECP5 FPGA board running a 64 MHz VexRiscv RISC-V softcore.
> >
> > Findings:
> >   - 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 logo (I have a custom monochrome logo enabled) is no longer shown.
>
> I was able to display your tux monochrome with ./fbtest -f /dev/fb1 test004

I meant the kernel's logo (FB_LOGO_*),. Obviously you need to enable
a smaller one, as the default 80x80 logo is too large, and thus can't
be drawn on your 128x64 or my 128x32 display.

> >   - The screen is empty, with a (very very slow) flashing cursor in the
> >     middle of the screen, with a bogus long line next to it, which I can
> >     see being redrawn.
> >   - Writing text (e.g. hello) to /dev/tty0, I first see the text,
> >     followed by an enlargement of some of the characters.
>
> So far I was mostly testing using your fbtest repo tests and all of them
> (modulo test009 that says "Screen size too small for this test").
>
> But I've tried now using as a VT and I see the same visual artifacts. I
> wonder what's the difference between fbcon and the way your tests use
> the fbdev API.

Fbcon does small writes to the shadow frame buffer, while fbtest
writes to the mmap()ed /dev/fbX, causing a full page to be updated.

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