On Tue, May 28, 2013 at 07:50:46AM +0200, Wolfgang Denk wrote: > Dear Tom, > > In message <20130527233735.GZ17119@bill-the-cat> you wrote: > > > > > Where exactly is this 8 MB limit coming into play? > > > > In buffering the data. We cannot write a chunk of a file to a > > filesystem and then append to it, we don't have the API today. > > Sorry, I still don't get it. Assuming I have a GiB of RAM, why can I > not load a 256 MiB file to RAM, and then write it to a file system? > > I have definitely dealt with images and files bigger than 8 MiB in > thepast, so I really don't see where any buffer problem could be.
I thought I might not have been clear about where this limit comes from, after I sent the email. The problem we have, and this is only for writing to a filesystem (_not_ writing of a filesystem) is that we do not have the API for appending to files, only create/overwrite. So we must read the whole file into memory, and then write it out. The DFU protocol doesn't have (I would swear anyhow) a part where it says "I'm about to send you a blob of X bytes", so we cannot know at the start how much data is coming our way. Today we "solve" this with a statically defined CONFIG_SYS_DFU_MAX_FILE_SIZE. Looking at things again, I think this is buggy right now in that we need to also whack DFU_DATA_BUF_SIZE to also be that same value. Going forward, we may be able to switch this to (and both of these are off the top of my head) a getenv to see how much space to malloc, or just making it a malloc and adding some compile-time check to ensure that the malloc area is at least as big as CONFIG_SYS_DFU_MAX_FILE_SIZE. -- Tom
signature.asc
Description: Digital signature
_______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
