From: Javier Martinez Canillas <javierm@redhat.com>
To: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: linux-kernel@vger.kernel.org,
"Daniel Vetter" <daniel.vetter@ffwll.ch>,
"Geert Uytterhoeven" <geert@linux-m68k.org>,
linux-fbdev@vger.kernel.org, "Sam Ravnborg" <sam@ravnborg.org>,
dri-devel@lists.freedesktop.org,
"Noralf Trønnes" <noralf@tronnes.org>,
"Thomas Zimmermann" <tzimmermann@suse.de>,
"Maxime Ripard" <maxime@cerno.tech>,
"Daniel Vetter" <daniel@ffwll.ch>,
"David Airlie" <airlied@linux.ie>,
"Lee Jones" <lee.jones@linaro.org>,
"Liam Girdwood" <lgirdwood@gmail.com>,
"Mark Brown" <broonie@kernel.org>,
"Thierry Reding" <thierry.reding@gmail.com>,
"Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>,
linux-pwm@vger.kernel.org
Subject: Re: [PATCH v2 2/4] drm/tiny: Add driver for Solomon SSD130X OLED displays
Date: Sat, 5 Feb 2022 18:40:08 +0100 [thread overview]
Message-ID: <8b87cbc8-4878-b320-9460-dac751f6f0d6@redhat.com> (raw)
In-Reply-To: <Yf511hhojzIXcNXp@smile.fi.intel.com>
On 2/5/22 14:04, Andy Shevchenko wrote:
> On Fri, Feb 04, 2022 at 08:19:12PM +0100, Javier Martinez Canillas wrote:
>> On 2/4/22 15:26, Andy Shevchenko wrote:
>>> On Fri, Feb 04, 2022 at 02:43:45PM +0100, Javier Martinez Canillas wrote:
>
> ...
>
>>>> +struct ssd130x_device {
>>>> + struct drm_device drm;
>>>> + struct drm_simple_display_pipe pipe;
>>>> + struct drm_display_mode mode;
>>>> + struct drm_connector connector;
>>>
>>>
>>>> + struct i2c_client *client;
>>>
>>> Can we logically separate hw protocol vs hw interface from day 1, please?
>>> This will allow to add SPI support for this panel much easier.
>>>
>>> Technically I would like to see here
>>>
>>> struct device *dev;
>>>
>>> and probably (I haven't looked into design)
>>>
>>> struct ssd130x_ops *ops;
>>>
>>> or something alike.
>>
>> Sure. I wanted to keep the driver simple, making the writes bus agnostic and
>> adding a level of indirection would make it more complex. But I agree that
>> it will also make easier to add more buses later. I will do that for v3.
>
> I have SSD1306 display with SPI interface and I'm not able to test your series.
> With the above it at least gives me a point to consider helping (coding and
> testing) with SPI one.
>
Yes, I understand that. On the other hand, I only have a SSD1306 with an I2C
interface so I'm interested in supporting that. Then someone could extend to
support other buses :)
But I agree with you that making the driver easier to extend and using regmap
would be desirable. In fact, since I will add the level of indirection I can
got ahead and attempt to add the SPI support as well.
I won't be able to test but I can use drivers/staging/fbtft/fb_ssd1306.c as a
reference for this.
> ...
>
>>>> + if (!fb)
>>>> + return;
>>>
>>> Can it happen?
>>
>> I don't know, but saw that the handler of other drivers checked for this so
>> preferred to play safe and do the same.
>
> So, either cargo-cult or indeed it may happen. Somebody may conduct a research
> on this...
>
Someone familiar with the simple display pipe helpers should chime in, I tried
to grep around but couldn't figure out whether it was safe or not to assume the
struct drm_framebuffer won't ever be NULL in a struct drm_shadow_plane_state.
As mentioned other drivers were doing and I preferred to be defensive rather
than leading to a possible NULL pointer dereference.
> ...
>
>>>> + drm_mode_probed_add(connector, mode);
>>>> + drm_set_preferred_mode(connector, mode->hdisplay, mode->vdisplay);
>>>> +
>>>> + return 1;
>>>
>>> Positive code, what is the meaning of it?
>>
>> It's the number of connector modes. The driver only supports 1.
>
> A comment then?
>
Yes, that makes sense.
Best regards,
--
Javier Martinez Canillas
Linux Engineering
Red Hat
next prev parent reply other threads:[~2022-02-05 17:40 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-04 13:43 [PATCH v2 0/4] drm/tiny: Add driver for Solomon SSD1307 OLED displays Javier Martinez Canillas
2022-02-04 13:43 ` [PATCH v2 1/4] drm/format-helper: Add drm_fb_{xrgb8888,gray8}_to_mono_reversed() Javier Martinez Canillas
2022-02-04 15:52 ` Thomas Zimmermann
2022-02-04 16:00 ` Thomas Zimmermann
2022-02-04 19:31 ` Javier Martinez Canillas
2022-02-04 20:35 ` Thomas Zimmermann
2022-02-04 21:02 ` Ilia Mirkin
2022-02-07 12:44 ` [PATCH v2 1/4] drm/format-helper: Add drm_fb_{xrgb8888, gray8}_to_mono_reversed() Thomas Zimmermann
2022-02-04 13:43 ` [PATCH v2 2/4] drm/tiny: Add driver for Solomon SSD130X OLED displays Javier Martinez Canillas
2022-02-04 14:26 ` Andy Shevchenko
2022-02-04 19:19 ` Javier Martinez Canillas
2022-02-05 13:04 ` Andy Shevchenko
2022-02-05 17:40 ` Javier Martinez Canillas [this message]
2022-02-04 13:43 ` [PATCH v2 3/4] MAINTAINERS: Add entry for Solomon SSD130X OLED displays DRM driver Javier Martinez Canillas
2022-02-04 13:57 ` Andy Shevchenko
2022-02-04 14:12 ` Javier Martinez Canillas
2022-02-04 14:28 ` Andy Shevchenko
2022-02-04 14:33 ` Javier Martinez Canillas
2022-02-04 13:43 ` [PATCH v2 4/4] dt-bindings: display: ssd1307fb: Add myself as binding co-maintainer Javier Martinez Canillas
2022-02-09 22:14 ` Rob Herring
2022-02-04 14:31 ` [PATCH v2 0/4] drm/tiny: Add driver for Solomon SSD1307 OLED displays Geert Uytterhoeven
2022-02-04 14:37 ` Javier Martinez Canillas
2022-02-08 14:19 ` Geert Uytterhoeven
2022-02-08 15:10 ` Javier Martinez Canillas
2022-02-08 15:18 ` Mark Brown
2022-02-08 15:32 ` Javier Martinez Canillas
2022-02-08 15:23 ` Geert Uytterhoeven
2022-02-08 15:40 ` Javier Martinez Canillas
2022-02-08 17:19 ` Javier Martinez Canillas
2022-02-09 13:47 ` Andy Shevchenko
2022-02-09 14:27 ` Geert Uytterhoeven
2022-02-09 14:42 ` Javier Martinez Canillas
2022-02-09 15:32 ` Andy Shevchenko
2022-02-10 8:32 ` Maxime Ripard
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