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[98.183.112.25]) by smtp.gmail.com with ESMTPSA id 46e09a7af769-71a108e3235sm2283754a34.53.2024.11.11.09.31.20 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 11 Nov 2024 09:31:20 -0800 (PST) Message-ID: <1f176b63-5904-49bf-9b63-6db440493773@baylibre.com> Date: Mon, 11 Nov 2024 11:31:20 -0600 Precedence: bulk X-Mailing-List: linux-spi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC v4 05/15] spi: dt-bindings: add PWM SPI offload trigger To: Conor Dooley , Jonathan Cameron Cc: Mark Brown , Rob Herring , Krzysztof Kozlowski , Conor Dooley , =?UTF-8?Q?Nuno_S=C3=A1?= , =?UTF-8?Q?Uwe_Kleine-K=C3=B6nig?= , Michael Hennerich , Lars-Peter Clausen , David Jander , Martin Sperl , linux-spi@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-iio@vger.kernel.org, linux-pwm@vger.kernel.org References: <20241023-dlech-mainline-spi-engine-offload-2-v4-0-f8125b99f5a1@baylibre.com> <20241023-dlech-mainline-spi-engine-offload-2-v4-5-f8125b99f5a1@baylibre.com> <20241026161837.30a56ae1@jic23-huawei> <20241031-croon-boss-3b30ff9e9333@spud> Content-Language: en-US From: David Lechner In-Reply-To: <20241031-croon-boss-3b30ff9e9333@spud> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 10/31/24 1:16 PM, Conor Dooley wrote: > On Sat, Oct 26, 2024 at 04:18:37PM +0100, Jonathan Cameron wrote: >> On Wed, 23 Oct 2024 15:59:12 -0500 >> David Lechner wrote: >> >>> Add a new binding for using a PWM signal as a trigger for SPI offloads. >> >> I don't have a better suggestion for this, but it does smell rather like >> other bridge binding (iio-hwmon for example) where we have had push back on >> representing something that doesn't really exist but is just a way to >> tie two bits of hardware together. Those kind of exist because we snuck >> them in a long time back when no one was paying attention. > > I dunno. iio-hwmon to me is a particularly strange one, because it is > the exact same device being used in different subsystems. Like that > voltage monitoring device with 10000 compatibles that I CCed you and > Peter on the other day feels like it should really in your subsytem. A > "hwmon" isn't a class of device at all. > > This however, I think is more like pwm-clock (or clk-pwm, they both > exist and are opposites) where the node is used to change the type of > device rather than the subsystem using it. Yes, this is the key reason for the binding. When I was looking at the trigger bindings in the leds subsystem, I came to the realization that we need some way to get the underlying type of the trigger. In the leds bindings, I don't think this was intentional, but effectively this is done with the linux,default-trigger property. So unless there is a reason why copying the clk-pwm/pwm-clock style bindings is not a good idea, that seems the preferable way to do it to me and I'll stick with that. > >> So this one may need more explanation and justification and I'd definitely >> like some DT maintainer review on this at a fairly early stage! > > Ye, /shrug. Maybe the others have dissenting opinions. I'd like to hear > from them, but I don't personally have a problem with this.