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Mon, 02 Oct 2023 02:25:12 -0700 (PDT) Date: Mon, 2 Oct 2023 17:25:05 +0800 From: Kent Gibson To: Andy Shevchenko Cc: Linus Walleij , Bartosz Golaszewski , Yury Norov , linux-gpio@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Shubhrajyoti Datta , Srinivas Neeli , Michal Simek , Bartosz Golaszewski , Rasmus Villemoes , Marek =?iso-8859-1?Q?Beh=FAn?= Subject: Re: [PATCH v1 5/5] gpiolib: cdev: Utilize more bitmap APIs Message-ID: References: <20230926052007.3917389-1-andriy.shevchenko@linux.intel.com> <20230926052007.3917389-6-andriy.shevchenko@linux.intel.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20231002_022516_779575_29888B9E X-CRM114-Status: GOOD ( 25.05 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Oct 02, 2023 at 12:05:11PM +0300, Andy Shevchenko wrote: > On Wed, Sep 27, 2023 at 10:23:12PM +0800, Kent Gibson wrote: > > On Wed, Sep 27, 2023 at 04:59:34PM +0300, Andy Shevchenko wrote: > > > On Wed, Sep 27, 2023 at 09:49:35PM +0800, Kent Gibson wrote: > > > > On Wed, Sep 27, 2023 at 03:17:06PM +0300, Andy Shevchenko wrote: > > > > > On Wed, Sep 27, 2023 at 09:32:11AM +0800, Kent Gibson wrote: > > ... > > > > > > Yet, it opens a way to scale this in case we might have v3 ABI that let's say > > > > > allows to work with 512 GPIOs at a time. With your code it will be much harder > > > > > to achieve and see what you wrote about maintenance (in that case). > > > > > > > > v3 ABI?? libgpiod v2 is barely out the door! > > > > Do you have any cases where 64 lines per request is limiting? > > > > > > IIRC it was SO question where the OP asks exactly about breaking the 64 lines > > > limitation in the current ABI. > > > > > > > If that sort of speculation isn't premature optimisation then I don't know > > > > what is. > > > > > > No, based on the real question / discussion, just have no link at hand. > > > But it's quite a niche, I can agree. > > > > Let me know if you find a ref to that discussion - I'm curious. > > Here it is (read comments as well): > https://stackoverflow.com/questions/76307370/control-gpio-from-linux-userspace-with-linux-gpio-h > That question looks to me to be confusing how many GPIOs can be requested per request (64) and in total (effectively unlimited) - thinking they are the same. That could be due to their desire to use the gpiod_chip_get_all_lines() convenience function with a chip with more than 64 lines, rather than because they have an actual need for the lines to be managed in a single request. So that doesn't look like a genuine use case to me - just a "what if I want to do X" question. Certainly not something that would warrant a v3 ABI. Cheers, Kent. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel