Dear Pantelis Antoniou, On Tuesday, May 28, 2013 5:05:12 PM, Pantelis Antoniou wrote: > Hi Tom, > > On May 28, 2013, at 6:01 PM, Tom Rini wrote: > > > 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. > > > > Correct, the DFU protocol doesn't have a method to inform you before hand > about the size of the transfer about to happen. > > The only possible solution I see at this point is to have an environment > variable, i.e. dfubuf that controls the size of the buffer. > > Upon start of a dfu transfer we can allocate the buffer, and do our > thing.
I don't know the details of the DFU implementation in U-Boot, but the specification leaves the choice between programming the firmware on-the-fly during the download, and later during the manifestation phase (or a mix of both). Hence, there is not need for a global firmware buffer if U-Boot goes for the on-the-fly programming strategy. The only buffer constraint would be wTransferSize (chosen by U-Boot for the control endpoint) in that case. See "7. Manifestation Phase" on page 26 here: http://www.usb.org/developers/devclass_docs/DFU_1.1.pdf Of course this can't yet apply to writing files on file systems since the current API in U-Boot misses the append feature, but this could be applied to program raw memory partitions, including UBI images. Best regards, Benoît _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
