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[92.176.231.205]) by smtp.gmail.com with ESMTPSA id g26-20020a7bc4da000000b003f60e143d38sm6287776wmk.11.2023.06.10.10.51.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 10 Jun 2023 10:51:42 -0700 (PDT) From: Javier Martinez Canillas To: Conor Dooley Cc: devicetree@vger.kernel.org, Conor Dooley , Thomas Zimmermann , Krzysztof Kozlowski , linux-kernel@vger.kernel.org, Maxime Ripard , Rob Herring , Geert Uytterhoeven , dri-devel@lists.freedesktop.org Subject: Re: [PATCH v2 2/5] dt-bindings: display: ssd1307fb: Remove default width and height values In-Reply-To: <20230610-opposite-quality-81d4a1561c88@spud> References: <20230609170941.1150941-1-javierm@redhat.com> <20230609170941.1150941-3-javierm@redhat.com> <20230610-opposite-quality-81d4a1561c88@spud> Date: Sat, 10 Jun 2023 19:51:35 +0200 Message-ID: <87r0qj19zs.fsf@minerva.mail-host-address-is-not-set> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Conor Dooley writes: > On Fri, Jun 09, 2023 at 07:09:37PM +0200, Javier Martinez Canillas wrote: >> A default resolution in the ssd130x driver isn't set to an arbitrary 96x16 >> anymore. Instead is set to a width and height that's controller dependent. > > Did that change to the driver not break backwards compatibility with > existing devicetrees that relied on the default values to get 96x16? > It would but I don't think it is an issue in pratice. Most users of these panels use one of the multiple libraries on top of the spidev interface. For the small userbase that don't, I believe that they will use the rpif kernel and ssd1306-overlay.dtbo DTB overlay, which defaults to width=128 and height=64 [1]. So those users will have to explicitly set a width and height for a 96x16 panel anyways. The intersection of users that have a 96x16 panel, assumed that default and consider the DTB a stable ABI, and only update their kernel but not the DTB should be very small IMO. [1]: https://github.com/raspberrypi/linux/blob/rpi-6.1.y/arch/arm/boot/dts/overlays/ssd1306-overlay.dts > Cheers, > Conor. > -- Best regards, Javier Martinez Canillas Core Platforms Red Hat