linux-kernel - Re: [PATCH 3/3] drm/ssd130x: Change "solomon,page-offset" property default value

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Message-ID: <yqneztpzmhhqenommpvhw2pksjspq7srpeba7ckfia5z3c5aap@wmnxhbgcflnd>
Date:   Fri, 17 Nov 2023 09:38:13 +0100
From:   Maxime Ripard <mripard@...nel.org>
To:     Javier Martinez Canillas <javierm@...hat.com>
Cc:     linux-kernel@...r.kernel.org, Sahaj Sarup <sahaj.sarup@...aro.org>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...il.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH 3/3] drm/ssd130x: Change "solomon,page-offset" property
 default value

On Thu, Nov 16, 2023 at 07:07:39PM +0100, Javier Martinez Canillas wrote:
> This is used to specify the page start address offset of the display RAM.
> 
> The value is used as offset when setting the page start address with the
> SSD130X_SET_PAGE_RANGE command, and the driver currently sets its value to
> 1 if the property is not present in the Device Tree.
> 
> But the datasheet mentions that the value on reset for the page start is a
> 0, so it makes more sense to also have 0 as the default value for the page
> offset if the property is not present.

I can see the argument, but that's a DT ABI breaking change.

> In fact, using a default value of 1 leads to the display not working when
> the emulated fbdev is attached to the framebuffer console.

Could we fix that one instead? What is the issue about, exactly

Maxime

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