Hi Jon, Looks like we are treading similar ground ;-)
I have been considering a 'restore to factory default' feature (post upgrade catastrophy fix). I have been looking at using 'unionfs' to provide a single filesystem that is actually comprised of 2 partitions, one writeable and one read only. All writes to the file system pysically get written to the writable partition and attempts to delete files in the read only partition cause 'mask files' to appear in the writable partition that make the file disappear when viewed from the union. We can at any time go back to 'factory' conditions by simply erasing the writeable partition. This is the technique the Asus EeePC uses. Unfortunately on the 2.6.10 kernel, unionfs ran fine for a day or so but then silently locked up the board. I was going to try 'aufs' (as used by Slax) but have not had the time to progress it. Also my first effort 'unioned' the whole filesytem - it might be better to only do part of the filesytem. Regards Phil Q Phil Quiney, Principal Software Engineer Trinity Convergence Cambridge Business Park Cowley Road Cambridge CB4 0WZ, UK T: +44(0)1223-435536 F: +44(0)1223-435560 www.trinityconvergence.com -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Jon Povey Sent: 14 October 2008 14:15 To: [EMAIL PROTECTED]; [email protected] Subject: RE: DM355 bootloader Phil wrote: > AFAIK 'UBL' is the U-Boot Loader - that is a very small program that > copies the U-Boot image from NAND into RAM and runs it. This may well > be an assembly language program (I have never had any reason to study > it) so good luck if you want to change it. The UBL is a TI app, I think it stands for "User Boot Loader" (At least on DM355). I have seen source for it, somewhere.. UBL is needed because u-boot can't load itself from NAND flash, and you can't do XIP. Confusing side-note: I'm a bit less sure why the RBL can't load u-boot directly.. I think I worked it out at some point, it's because the RBL can only load something that fits into one block, or something like that. The TI UBL is just a little bit of glue between RBL and u-boot, as I understand it. > U-Boot is the boot loader. It allows rudimentary access to the FLASH > and RAM on the board and typically a way of loading an operating > system kernel. Integrating an app updater into this may be a challenge > especially as it knows nothing about JFFS/YAFFS filesystems. You may > be able to FLASH the entire filesystem but that gets interesting if > the filesystem image won't fit in RAM and you have to know about any > bad blocks in the NAND as well. I am looking into how to do all this stuff on DM355 at the moment. My current plan is to have two copies of the kernel, two entirely separate filesystem partitions, and update one while the other is running, then switch (probably by changing u-boot environment variables). -- Jon Povey, Design Engineer [EMAIL PROTECTED] | +44(0)1280 825983 Racelogic is a limited company registered in England. Registered number 2743719 . Registered Office Unit 10, Swan Business Centre, Osier Way, Buckingham, Bucks, MK18 1TB . The information contained in this electronic mail transmission is intended by Racelogic Ltd for the use of the named individual or entity to which it is directed and may contain information that is confidential or privileged. If you have received this electronic mail transmission in error, please delete it from your system without copying or forwarding it, and notify the sender of the error by reply email so that the sender's address records can be corrected. The views expressed by the sender of this communication do not necessarily represent those of Racelogic Ltd. Please note that Racelogic reserves the right to monitor e-mail communications passing through its network _______________________________________________ Davinci-linux-open-source mailing list [email protected] http://linux.davincidsp.com/mailman/listinfo/davinci-linux-open-source
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