From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 467BB1DA4B for ; Mon, 20 Nov 2023 15:50:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="OuakXYfH" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2A91EC433C7; Mon, 20 Nov 2023 15:50:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1700495425; bh=hwGdvTC30e2lqKVVWjBXy5T6ES/s37IXoRVGMd2+0pQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=OuakXYfH2B3OCYrq02ImXPaLKHHgv1XoOxq2euxeIQWC0Crhms/GQfyHAERvfK69s DF1RBMamEUYPuaOfpnaQp1j+CNzucEdp1EpNAPN+hWMv57j1T/49wvYAu20TggHUvr 9h9mFblafUh5Qh+JN7xv4j9enLyvvjGgt/YK2XvQvOmhX4pbud5Uo9wJI5ysIkZrNw BPWdpOl8U5S3cdCW/wUONBUm0CW8H5dyUUZJsDljmdbgfcn5XTMVRFnoX/B5WCXJTP PyXPoKPqTJYSNuJDOUBMqvy72xpUWxgQ/NsRdT6CL/dMnTLhYok/ymvlzSQA5CyIvF LZZLM4LJ/KWzQ== Date: Mon, 20 Nov 2023 15:50:20 +0000 From: Conor Dooley To: Javier Martinez Canillas Cc: linux-kernel@vger.kernel.org, Sahaj Sarup , Conor Dooley , Daniel Vetter , David Airlie , Krzysztof Kozlowski , Maarten Lankhorst , Maxime Ripard , Rob Herring , Thomas Zimmermann , devicetree@vger.kernel.org, dri-devel@lists.freedesktop.org Subject: Re: [PATCH 1/3] dt-bindings: display: ssd1307fb: Change "solomon,page-offset" default value Message-ID: <20231120-granola-sturdy-83d054f1b6fa@spud> References: <20231116180743.2763021-1-javierm@redhat.com> Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="4bFoAD9+noYJcHZh" Content-Disposition: inline In-Reply-To: <20231116180743.2763021-1-javierm@redhat.com> --4bFoAD9+noYJcHZh Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Nov 16, 2023 at 07:07:37PM +0100, Javier Martinez Canillas wrote: > This is used to specify the page start address offset of the display RAM. >=20 > 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. >=20 > 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. >=20 > In fact, using a default value of 1 leads to the display not working when > the fbdev is attached to the framebuffer console. >=20 > Reported-by: Sahaj Sarup > Signed-off-by: Javier Martinez Canillas > --- >=20 > .../devicetree/bindings/display/solomon,ssd1307fb.yaml | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) >=20 > diff --git a/Documentation/devicetree/bindings/display/solomon,ssd1307fb.= yaml b/Documentation/devicetree/bindings/display/solomon,ssd1307fb.yaml > index 3afbb52d1b7f..badd81459aaa 100644 > --- a/Documentation/devicetree/bindings/display/solomon,ssd1307fb.yaml > +++ b/Documentation/devicetree/bindings/display/solomon,ssd1307fb.yaml > @@ -35,7 +35,7 @@ properties: > =20 > solomon,page-offset: > $ref: /schemas/types.yaml#/definitions/uint32 > - default: 1 > + default: 0 I think I saw it pointed out by Maxime elsewhere that this breaks the ABI. It would be nice if DT defaults matched the hardware's, but I don't really think it is worth breaking the ABI here. Expanding the property description to explain the impact of the particular values might help with incorrect usage. Thanks, Conor. > description: > Offset of pages (band of 8 pixels) that the screen is mapped to > =20 > --=20 > 2.41.0 >=20 --4bFoAD9+noYJcHZh Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iHUEABYIAB0WIQRh246EGq/8RLhDjO14tDGHoIJi0gUCZVuAPAAKCRB4tDGHoIJi 0rwwAQDwlz5bsqGXaRqTo+gxHO6qWygSskpfqHWje4LOQ/STSAEAjptBSDLIi9s1 DjGRyqKsN280gvpMTdz7FUpAEO1gZwg= =pjLO -----END PGP SIGNATURE----- --4bFoAD9+noYJcHZh--