From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from down.free-electrons.com ([37.187.137.238] helo=mail.free-electrons.com) by bombadil.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1aoKQc-00031n-UM for linux-mtd@lists.infradead.org; Fri, 08 Apr 2016 00:37:39 +0000 Date: Fri, 8 Apr 2016 02:37:13 +0200 From: Boris Brezillon To: Brian Norris Cc: Ezequiel Garcia , linux-mtd@lists.infradead.org, Jacek Anaszewski , linux-leds@vger.kernel.org Subject: Re: nand-disk LED trigger: to remove, or not to remove Message-ID: <20160408023713.181ffc4e@bbrezillon> In-Reply-To: <20160406180316.GA11756@localhost> References: <20160405195120.GA6111@laptop.cereza> <20160406180316.GA11756@localhost> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Wed, 6 Apr 2016 11:03:16 -0700 Brian Norris wrote: > On Tue, Apr 05, 2016 at 04:51:20PM -0300, Ezequiel Garcia wrote: > > Due to the way the 'nand-disk' LED trigger is implemented, > > it currently does not work correctly for all NAND drivers. > >=20 > > This is somewhat related to an old thread, where we discussed > > the addition of an "mtd" LED trigger. See: > >=20 > > http://www.spinics.net/lists/linux-leds/msg01181.html > >=20 > > My question is: > >=20 > > * given that nobody has complained about "nand-disk" > > working on just some NAND drivers, and... > > * given that nobody has complained (except that 2013 patch) > > about lacking a generic MTD LED trigger... > >=20 > > Does it make any sense to have such a trigger at all? > > In other words, should we simply get rid of "nand-disk" trigger? >=20 > I don't have much opinion about the LED trigger, except that it'd be > nice if it either worked consistently or was removed. >=20 > > In case the answer is "We want to keep some LED trigger", > > then here's a patch for you to f=CC=B6l=CC=B6a=CC=B6m=CC=B6e=CC=B6 rev= iew: > >=20 > > From 88c7102bb67056b443da323bd3e28b60aca948a2 Mon Sep 17 00:00:00 2001 > > From: Ezequiel Garcia > > Date: Sat, 2 Apr 2016 18:35:50 -0300 > > Subject: [PATCH] leds: trigger: Introduce a MTD (NAND/NOR) trigger > >=20 > > This commit introduces a MTD trigger for flash (NAND/NOR) device > > activity. The implementation is copied from IDE disk. > >=20 > > This deprecates the "nand-disk" LED trigger, but for backwards > > compatibility, we still keep the "nand-disk" trigger around. > >=20 > > The motivation for deprecating the "nand-disk" LED trigger is that > > it only works for NAND drivers, whereas the "mtd" LED trigger > > is more generic (in fact, "nand-disk" currently only works for > > certain NAND drivers). > >=20 > > TODO: Measure how the trigger affects MTD I/O performance. > > It should be cheap because the blink is deferred, but still > > it makes sense to provide some hard numbers. > >=20 > > Signed-off-by: Ezequiel Garcia >=20 > [...] >=20 > Notably, your patch changes the behavior pretty significantly. Instead > of triggering for individual NAND wait periods (very fine-grained) you > only trigger for entire write/read/erase operations. Hm, I don't think the blinking frequency can be considered a stable ABI :-). Anyway, most of the time, read/write coming from FS are done on a per-page basis (except for the UBI/UBIFS maintenance operations), so it should pretty much match the existing behavior. > That may be OK, > especially if it's modelled after IDE. >=20 > I'd also note that you missed a few APIs (e.g., mtd_{read,write}_oob()). Yep, I forgot to mention that in my review. --=20 Boris Brezillon, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com