[U-Boot] [PATCH 3/3] dfu: Introduction of the "dfu_checksum_method" env variable for checksum method setting

[Lukasz Majewski]

Hi Tom,

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> On 03/31/2014 04:44 PM, Lukasz Majewski wrote:
> > On Mon, 31 Mar 2014 14:05:17 -0400
> > Tom Rini <trini at ti.com> wrote:
> > 
> >> On Mon, Mar 31, 2014 at 10:48:49AM +0200, Lukasz Majewski wrote:
> >>
> >>> Up till now the CRC32 of received data was calculated
> >>> unconditionally. The standard crc32 implementation causes long
> >>> delays when large images were uploaded.
> >>>
> >>> The "dfu_checksum_method" environment variable gives the
> >>> opportunity to enable on demand (when e.g. debugging) the crc32
> >>> calculation. It can be done without need to recompile the u-boot
> >>> binary.
> >>>
> >>> By default the crc32 is not calculated.
> >>>
> >>> Tests results:
> >>> 400 MiB ums.img file
> >>> With 		crc32 calculation: 65 sec [avg 6.29 MB/s]
> >>> Without 		crc32 calculation: 25 sec [avg 16.17 MB/s]
> >>>
> >>> Signed-off-by: Lukasz Majewski <l.majewski at samsung.com>
> >>
> >> OK, so, protocol question.
> > 
> > The DFU 1.1 standard in its appendinx B specifies the DFU suffix.
> > It has the crc32 for the whole file, vendorID, device ID and other
> > handy fields.
> > 
> > Unfortunately, this part of the standard is not supported neither at
> > dfu implementation in u-boot nor dfu-util (v.0.5 - debian).
> 
> OK, so this is the important part.  We're doing a crc32 on stuff
> that's not required by spec, just handy for verification, manually.

Yes, indeed.

> 
> [snip]
> > When we use CRC in such a way, we should be able to decide which
> > tool (algorithm) use for debug. SHA1, MD5, etc are widely available
> > on each linux box. To have the same crc32 algorithm, which is in
> > u-boot, implemented as linux command line tool you need to search a
> > bit (libarchive-zip-perl package for debian).
> 
> I take your point, but I use rhash -C to get matching crc32 and it was
> the first thing I stumbled upon when going "oh right, what does
> crc32?".
> 
> [snip]
> 
> > TO SUM UP:
> > 
> > 1. Handling of the DFU suffix shall be implemented and utilized in
> > both u-boot and dfu-util with critical files (bootloaders, kernel).
> > 
> > 2. There should be freedom to use different checksum algorithms for
> > providing debugging information.
> > 
> > 3. The current CRC32 calculation at DFU should be optimized.
> 
> Well, is there work being done on the dfu-util side currently or
> planned in the near future to do #1 per the spec?

As Tormod has written, dfu-util supports it for initial setting, but is
sending data with this information stripped. Hence u-boot shall not
calculate CRC32 unless we plan to add a customized prefix for crucial
binaries.

> 
> But, with that, I'm happier to default to no crc32'ing the data for
> today.

Thanks for your opinion. We share similar view on the issue.

> 
> - -- 
> Tom
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-- 
Best regards,

Lukasz Majewski

Samsung R&D Institute Poland (SRPOL) | Linux Platform Group