From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Rafael J. Wysocki" Subject: Re: [PATCH v4 3/5] irqchip: Add DT binding doc for the virtual irq demuxer chip Date: Wed, 11 Feb 2015 17:42:22 +0100 Message-ID: <2067295.NbJCftPPli@vostro.rjw.lan> References: <1422527620-8308-1-git-send-email-boris.brezillon@free-electrons.com> <20150211155720.GQ9154@leverpostej> <20150211171515.55d5066f@bbrezillon> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7Bit Return-path: In-Reply-To: <20150211171515.55d5066f@bbrezillon> Sender: linux-kernel-owner@vger.kernel.org To: Boris Brezillon Cc: Mark Rutland , Thomas Gleixner , Jason Cooper , Nicolas Ferre , Jean-Christophe Plagniol-Villard , Alexandre Belloni , Rob Herring , Pawel Moll , Ian Campbell , Kumar Gala , "devicetree@vger.kernel.org" , "Rafael J. Wysocki" , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" List-Id: devicetree@vger.kernel.org On Wednesday, February 11, 2015 05:15:15 PM Boris Brezillon wrote: > On Wed, 11 Feb 2015 15:57:20 +0000 > Mark Rutland wrote: > > > [...] > > > > > > > > So for the flag at request time approach to work, all the drivers using > > > > > > the interrupt would have to flag they're safe in that context. > > > > > > > > > > Something like IRQF_"I can share the line with a timer" I guess? That wouldn't > > > > > hurt and can be checked at request time even. > > > > > > > > I guess that would have to imply IRQF_SHARED, so we'd have something > > > > like: > > > > > > > > IRQF_SHARED_SUSPEND_OK - This handler is safe to call spuriously during > > > > suspend in the case the line is shared. The > > > > handler will not access unavailable hardware > > > > or kernel infrastructure during this period. > > > > > > > > #define __IRQF_SUSPEND_SPURIOUS 0x00040000 > > > > #define IRQF_SHARED_SUSPEND_OK (IRQF_SHARED | __IRQF_SUSPEND_SPURIOUS) > > > > > > What about > > > > > > #define __IRQF_TIMER_SIBLING_OK 0x00040000 > > > #define IRQF_SHARED_TIMER_OK (IRQF_SHARED | __IRQF_TIMER_SIBLING_OK) > > > > > > The "suspend" part is kind of a distraction to me here, because that really > > > only is about sharing an IRQ with a timer and the "your interrupt handler > > > may be called when the device is suspended" part is just a consequence of that. > > > > My rationale was that you didn't really care who else was using the IRQ > > (e.g. the timer); you're just stating that you can survive being called > > during suspend (which is what the driver may need to check for in the > > handler if the device happens to be powered down or whatever). > > > > So I guess I see it the other way around. This is essentially claiming > > we can handle sharing with IRQF_NO_SUSPEND rather than IRQF_TIMER. > > > > > So IMO it's better to have "TIMER" in the names to avoid encouraging people to > > > abuse this for other purposes not related to timers. > > > > In the end a name is a name, and if you think IRQF_SHARED_TIMER_OK is > > better I shan't complain. > > > > The fundamental issue I'm concerned with is addressed by this approach. > > Okay then, is anyone taking care of submitting such a patch (Mark ?) ? Well, I guess I should take the responsibility for that. :-) I'll try to cut one later today or tomorrow unless someone else beats me to that. Rafael