From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marco Stornelli Subject: Re: [PATCH 00/17] pramfs: persistent and protected RAM filesystem Date: Thu, 06 Jan 2011 19:31:50 +0100 Message-ID: <4D260A96.4020400@gmail.com> References: <4D25AEEE.1050401@gmail.com> <1294322613.2016.333.camel@laptop> <4D25ED22.3070900@gmail.com> <4D25F4CF.1030009@gmail.com> <987664A83D2D224EAE907B061CE93D530193FC6AA2@orsmsx505.amr.corp.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Peter Zijlstra , Linux Kernel , Linux FS Devel , Linux Embedded , Tim Bird To: "Luck, Tony" Return-path: In-Reply-To: <987664A83D2D224EAE907B061CE93D530193FC6AA2@orsmsx505.amr.corp.intel.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org Il 06/01/2011 19:22, Luck, Tony ha scritto: >> Errata corrige: maybe I used the wrong term, I meant "volatile" instead >> of "temporary" information, i.e. I'd like to save this info to re-read >> it later but I don't want to store it in flash, a simple log, run-time >> information for debug like a flight-recorder or whatever you want. > > I'm puzzled by the use of "a generic piece of memory" to store "persistent" > things (Perhaps this is made clear in the 17 parts of the patch? I haven't > read them yet). On x86 f/w typically clears all of memory on reset ... so > you only get persistence if you use kexec to get from the old kernel to > the new one. > > -Tony > First of all, you can find a lot of information on the web site where there is an overview and a page with implementation details, benchmark and so on. With "a generic piece of memory" I mean a generic memory device directly addressable. Usually this generic device is an NVRAM, so we have a persistent store. If you haven't got this hw you can use other devices or the classic RAM, in this case you have a fs persistent only over reboot. The use of this fs is mainly for embedded systems, fw can be configured to not clear *all* the memory. Pramfs is indeed supported by U-Boot, you can see CONFIG_PRAM in the Das U-Boot manual. x86 in this case can be a "strange" world for this fs, but however if the user wants it can be used without problems because there aren't neither strict arch or hw dependency. Marco