From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.sigma-star.at ([95.130.255.111]) by casper.infradead.org with esmtp (Exim 4.87 #1 (Red Hat Linux)) id 1eMX8R-0007sj-JX for linux-mtd@lists.infradead.org; Wed, 06 Dec 2017 10:41:05 +0000 From: Richard Weinberger To: Dirk Behme Cc: linux-mtd@lists.infradead.org, manfred@colorfullife.com, boris.brezillon@free-electrons.com, david.oberhollenzer@sigma-star.at Subject: Re: [PATCH 0/5] Add flight recorder to MTDRAM Date: Wed, 06 Dec 2017 11:41:10 +0100 Message-ID: <252100234.Y1JYG21Gen@blindfold> In-Reply-To: <20171206085039.27164-1-dirk.behme@de.bosch.com> References: <20171206085039.27164-1-dirk.behme@de.bosch.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Dirk, Manfred, Am Mittwoch, 6. Dezember 2017, 09:50:34 CET schrieb Dirk Behme: > From: Manfred Spraul > > Hi, > > The series adds a flight recorder to MTDRAM. Thanks a lot for sharing your tool, this is highly appreciated. > This allows very efficient power fail testing: > From the flight recorder output, it is possible to recreate every image > that might have existed between the start of the recording and the end. > > Obviously, a user space tool is required, it is attached as the last > mail in the series. So, to understand this approach better I need to recap. The "flight recorder" logs every single MTD operation (READ, ERASE, PROGRAM) to a file while the MTD is under load, right? Then you take the log, replay it to a _file_ but instead of replaying all N MTD operations only N - X operations are replayed? The output file is later written back to MTDRAM to check how much UBIFS likes it? While having such a tool would be awesome, we have to be very sure that it behaves correctly. Yesterday I spent almost the whole night with staring at some of Manfred's images and I'm not sure whether what I see makes sense or can actually happen on a real NAND or NOR flash. But I'm still investigating. > Patches: > > 0001-mtdram-expose-write-size-and-writebuf-size-as-module: > An initial cleanup: write_size and writebuf_size are > hardcoded in the source code. > Convert that to module parameters. MTDRAM is a special purpose MTD simulator, I'm not so sure whether it is a good idea to turn it into a NAND-alike zombie. I said this already some time before, Boris and I are in general unhappy with the current MTD simulator zoo in MTD. But fixing this is not your job, we have to. :-) Thanks, //richard