[U-Boot] dfu: dfu and UBI Volumes

[Tom Rini <trini@ti.com>]

On Tue, May 28, 2013 at 07:55:03AM +0200, Wolfgang Denk wrote:
> Dear Heiko,
> 
> In message <51A427A8.8090709@denx.de> you wrote:
> >
> > > Where exactly is this 8 MB limit coming into play?
> > 
> > You find this in drivers/dfu/dfu.c:
> > 
> > static unsigned char __aligned(CONFIG_SYS_CACHELINE_SIZE)
> >                                    dfu_buf[DFU_DATA_BUF_SIZE];
> 
> Ah, so it is a DFU restriction!
[snip]
> > drivers/dfu/dfu_mmc.c use (another?, why?) buffer:
> > 
> > static unsigned char __aligned(CONFIG_SYS_CACHELINE_SIZE)
> >                                 dfu_file_buf[CONFIG_SYS_DFU_MAX_FILE_SIZE];
> ...
> > and use this buffer for not raw partitions ... and this buffer
> > gets flushed, only if the complete file is transfered, as the
> > README states:
> > 
> >                 CONFIG_SYS_DFU_MAX_FILE_SIZE
> >                 When updating files rather than the raw storage device,
> >                 we use a static buffer to copy the file into and then write
> >                 the buffer once we've been given the whole file.  Define
> >                 this to the maximum filesize (in bytes) for the buffer.
> >                 Default is 4 MiB if undefined.
> 
> This makes very little sense to me.  Why do we need another (and even
> smaller) buffer when we already have one?

Per my other email, the intention and implementation didn't quite
match-up.  The intent of the README should be (but isn't) reflected) in
the code.  And perhaps we can come up with something better than a big
static allocation.  Perhaps.

-- 
Tom
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