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[82.37.195.13]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4806e2e5ffcsm4307315e9.18.2026.01.28.03.20.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 28 Jan 2026 03:20:59 -0800 (PST) Date: Wed, 28 Jan 2026 11:20:56 +0000 From: Daniel Thompson To: Krzysztof Kozlowski Cc: tessolveupstream@gmail.com, lee@kernel.org, danielt@kernel.org, jingoohan1@gmail.com, deller@gmx.de, pavel@kernel.org, robh@kernel.org, krzk+dt@kernel.org, conor+dt@kernel.org, dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org, linux-leds@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 1/2] dt-bindings: backlight: gpio-backlight: allow multiple GPIOs Message-ID: References: <20260120125036.2203995-1-tessolveupstream@gmail.com> <20260120125036.2203995-2-tessolveupstream@gmail.com> <3f3c47ea-1660-4bd4-ab89-3bdf58217995@kernel.org> <54d156ba-e177-4059-a808-2505983b4e2e@gmail.com> <500b603d-5abc-4c45-8d56-bbc88fc85b83@kernel.org> Precedence: bulk X-Mailing-List: linux-fbdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <500b603d-5abc-4c45-8d56-bbc88fc85b83@kernel.org> On Wed, Jan 28, 2026 at 11:11:33AM +0100, Krzysztof Kozlowski wrote: > On 23/01/2026 12:11, tessolveupstream@gmail.com wrote: > > > > > > On 20-01-2026 20:01, Krzysztof Kozlowski wrote: > >> On 20/01/2026 13:50, Sudarshan Shetty wrote: > >>> Update the gpio-backlight binding to support configurations that require > >>> more than one GPIO for enabling/disabling the backlight. > >> > >> > >> Why? Which devices need it? How a backlight would have three enable > >> GPIOs? I really do not believe, so you need to write proper hardware > >> justification. > >> > > > > To clarify our hardware setup: > > the panel requires one GPIO for the backlight enable signal, and it > > also has a PWM input. Since the QCS615 does not provide a PWM controller > > for this use case, the PWM input is connected to a GPIO that is driven > > high to provide a constant 100% duty cycle, as explained in the link > > below. > > https://lore.kernel.org/all/20251028061636.724667-1-tessolveupstream@gmail.com/T/#m93ca4e5c7bf055715ed13316d91f0cd544244cf5 > > That's not an enable gpio, but PWM. > > You write bindings for this device, not for something else - like your > board. Sudarshan: I believe at one point the intent was to model this hardware as a pwm-backlight (using enables GPIOs to drive the enable pin) attached to a pwm-gpio (to drive the PWM pin). Did this approach work? Daniel.