Hi On May 28, 2013, at 7:43 PM, Benoît Thébaudeau wrote: > Hi Pantelis, > > On Tuesday, May 28, 2013 6:43:06 PM, Pantelis Antoniou wrote: >> Hi Benoît >> >> On May 28, 2013, at 7:31 PM, Benoît Thébaudeau wrote: >> >>> 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 >>> >> >> The problem is not DFU TBH, it's that since we don't have an option to append >> to a file, we have to have the whole file transferred in RAM and written in >> one go. The raw medium dfu methods in u-boot don't have a problem. >> >>> 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. >>> >> >> It already happens for raw memory partitions, it's the UBI images being >> discussed. > > But what does appending to a file has to do with programming a UBI image, > which > is a memory partition containing a whole file system? This is what I don't get > in this discussion. Is it because of a restriction of the DFU API in U-Boot? >
Don't expect a discussion on a mailing list to stay on topic for long :) We sort of drifted from UBI to the fixed sized buffer. > Best regards, > Benoît Regards -- Pantelis _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot