On Mon, Jul 07, 2008 at 01:47:24PM -0500, Scott Wood wrote: > On Mon, Jul 07, 2008 at 12:28:12AM +0800, Harald Welte wrote: > > I've first sent this on Feb 17, 2007. Unfortunately no reply was > > received. I think this is a quite useful feature, since a compile time > > offset into the NAND flash for the environment just doesn't work well > > with bad blocks ;) > > It works if you allow room for bad blocks within each partition, and treat > the environment as its own partition. Current u-boot supports skipping bad > blocks within a desginated environment region.
which wastes a lot of space, if you have something like a 128kByte erase-block-size (like most 2kByte page size NAND's today)... so if you want to have redundancy and use some spare blocks you will end up with something on the order of 512kByte of wasted flash space to store a couple of hundreds of bytes environment. Not very elegant. Furthermore, if you want to make sure it always works with any of your components that are within the spec of the manufacturer, then you will waste even more. The problem is that a new virgin component e.g. a 64MByte flash from Samsung can have already as many as 1.3MBytes of bad blocks. There is no guarantee that they are all within one of your partitions. So to only cope with factory bad blocks, you would have to have 1.3MBytes of spare space in each of your partitions! Don't you think that's a bit too much waste of space? (you can read the full rationale at http://wiki.openmoko.org/wiki/NAND_bad_blocks) So I'd say that having the address of the environment block stored in the out-of-band area of the first block (which is always guaranteed to be good by the manufacturer) sounds like a much more elegant solution. Therefore, I still believe that such a feature is useful and should be merged into u-boot. If there are problems with my particular implementation, I'm happy to address them. I also have another patchset for what I call 'dynpart' support, i.e. the dynamic calculation of a unit-specific partition table that ensures the net size of partitions are as per spec, no matter how many of the factory default blocks are located where. So it would even support NAND devices with a worse spec than the ones that we were using. Cheers, -- - Harald Welte <[EMAIL PROTECTED]> http://openmoko.org/ ============================================================================ Software for the world's first truly open Free Software mobile phone ------------------------------------------------------------------------- Sponsored by: SourceForge.net Community Choice Awards: VOTE NOW! Studies have shown that voting for your favorite open source project, along with a healthy diet, reduces your potential for chronic lameness and boredom. Vote Now at http://www.sourceforge.net/community/cca08 _______________________________________________ U-Boot-Users mailing list U-Boot-Users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/u-boot-users
