linux-kernel - Re: [PATCH v6 3/6] drm: Add driver for Solomon SSD130x OLED displays

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Message-ID: <8cbfcc29-bc31-9bc8-2eaa-d873f7cf2d5f@redhat.com>
Date:   Mon, 13 Jun 2022 19:41:25 +0200
From:   Javier Martinez Canillas <javierm@...hat.com>
To:     "andriy.shevchenko@...ux.intel.com" 
        <andriy.shevchenko@...ux.intel.com>,
        Dominik Kierner <dkierner@...electronics.com>
Cc:     "airlied@...ux.ie" <airlied@...ux.ie>,
        "daniel.vetter@...ll.ch" <daniel.vetter@...ll.ch>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "geert@...ux-m68k.org" <geert@...ux-m68k.org>,
        "lee.jones@...aro.org" <lee.jones@...aro.org>,
        "linux-fbdev@...r.kernel.org" <linux-fbdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-pwm@...r.kernel.org" <linux-pwm@...r.kernel.org>,
        "maxime@...no.tech" <maxime@...no.tech>,
        "noralf@...nnes.org" <noralf@...nnes.org>,
        "sam@...nborg.org" <sam@...nborg.org>,
        "thierry.reding@...il.com" <thierry.reding@...il.com>,
        "tzimmermann@...e.de" <tzimmermann@...e.de>,
        "u.kleine-koenig@...gutronix.de" <u.kleine-koenig@...gutronix.de>
Subject: Re: [PATCH v6 3/6] drm: Add driver for Solomon SSD130x OLED displays

On 6/13/22 17:35, andriy.shevchenko@...ux.intel.com wrote:
> On Mon, Jun 13, 2022 at 11:39:30AM +0000, Dominik Kierner wrote:
>> On 5/25/2022 21:46, Javier Martinez Canillas wrote:
> 
> ...
> 
>>> Thanks, I looked at the code briefly and think that there are things there that we
>>> could use. I.e the 3-wire SPI support that's in panel-solomon-ssd130x-spi-3wire.c.
>>
>> When writing my driver code, I wasn't even considering using regmaps,
>> like You did in Your I2C-Code. If that's applicable for 3-wire-SPI,
>> it would likely be the better, more generic option. Your SPI-code
>> reuses these parts to some extent. For that case,
>> ssd130x_spi_regmap_config.reg_bits would need be changed to 1,
>> as the "register address" has a length of 1 bit and we are sending
>> 9 bits over the line and not 16.
>> Since we still have 2 bytes of host memory,
>> it should still be compatible with the 4-wire write, right?
>> Or would 3-wire SPI require a second regmap?
> 
> I believe the cleanest solution is to have different regmap configurations.
> 

I agree with this.

-- 
Best regards,

Javier Martinez Canillas
Linux Engineering
Red Hat