From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Wed, 17 Dec 2014 10:04:24 -0600 (CST) From: Aaron Sierra To: Brian Norris , Ricard Wanderlof Message-ID: <488523809.20376.1418832264672.JavaMail.zimbra@xes-inc.com> In-Reply-To: References: <1683475520.65208.1411665491176.JavaMail.zimbra@xes-inc.com> <673100209.65720.1411665624206.JavaMail.zimbra@xes-inc.com> <20141217023344.GS9759@ld-irv-0074> Subject: Re: [PATCH 2/2] mtd: map_rom: Support UBI on ROM MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: David Woodhouse , linux-mtd@lists.infradead.org List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , ----- Original Message ----- > From: "Ricard Wanderlof" > Sent: Wednesday, December 17, 2014 3:37:42 AM > > On Wed, 17 Dec 2014, Brian Norris wrote: > > > But then I'm curious: how do you get anything useful out of using UBI on > > a read-only device? You don't need to (and can't) handle anything like > > read disturb, and there's no write wear that needs to be leveled. > > Don't know about this particular case, but in some cases it can be an > advantage to be able to use the same file system image in both a read-only > and a writable environment. > > Say you have some form of ROM device with no bit flips, but occasionally > (e.g. during development) you want to use the same file system image in a > flash. While the same thing can be accomplished by using seperate file > systems which share the same content, it can simplify the whole system if > only one file system image is needed which can reside in multiple types of > media. Thanks Ricard, you have touched on the scenario that I am concerned about. The environment in our case is a single-board computer that can become read-only based on a hardware jumper or signal from a backplane. It would be tedious to _have_ to prepare a separate image in order to install the SBC into a backplane that forces the NOR into read-only operation. Instead, we find it advantageous to be able to simply freeze the state of the UBI filesytem until the SBC is moved back to a read-write environment for further development. -Aaron