From mboxrd@z Thu Jan 1 00:00:00 1970 From: Linus Walleij Subject: Re: [PATCH v4] gpio: lib-sysfs: Add 'wakeup' attribute Date: Mon, 19 Jan 2015 09:54:58 +0100 Message-ID: References: <1421351389-11660-1-git-send-email-soren.brinkmann@xilinx.com> <20150116111108.GG30960@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: Sender: linux-gpio-owner@vger.kernel.org To: Alexandre Courbot Cc: =?UTF-8?Q?S=C3=B6ren_Brinkmann?= , Johan Hovold , linux-api@vger.kernel.org, Linux Kernel Mailing List , "linux-gpio@vger.kernel.org" , "linux-doc@vger.kernel.org" List-Id: linux-api@vger.kernel.org On Mon, Jan 19, 2015 at 5:20 AM, Alexandre Courbot w= rote: > On Sat, Jan 17, 2015 at 1:49 AM, S=C3=B6ren Brinkmann wrote: >> On Fri, 2015-01-16 at 12:11PM +0100, Johan Hovold wrote: >>> Implementing proper wakeup support for unclaimed GPIOs would take s= ome >>> work (if at all desired), but that is not a reason to be adding cus= tom >>> implementations that violates the kernel's power policies and new A= BIs >>> that would need to be maintained forever. (...) >>> Meanwhile you can (should) use gpio-keys if you need to wake your s= ystem >>> on gpio events. >> >> We had that discussion and I don't think GPIO keys is the right solu= tion >> for every use-case. > > Sorry, it has been a while - can you remind us of why? There are such cases. Of course keys should be handled by GPIO-keys and these will trigger the right wakeup events in such cases. This is for more esoteric cases: we cannot have a kernel module for everything people want to do with GPIOs, and the use case I accept is GPIOs used in automatic control etc, think factory lines or doors. We can't have a "door" driver or "punch arm" or "fire alarm" driver in the kernel. Those are userspace things. Still such embedded systems need to be able to go to idle and sleep to conerve power, and then they need to put wakeups on these GPIOs. So it is a feature userspace needs, though as with much of the sysfs ABI it is very often abused for things like keys and LEDs which is an abomination but we can't do much about it :( Yours, Linus Walleij -- To unsubscribe from this list: send the line "unsubscribe linux-gpio" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html