[U-Boot] [PATCH 0/6] add zip command support for uboot

[Lei Wen]

Hi Marek,

On Wed, Sep 26, 2012 at 11:34 PM, Marek Vasut <marex at denx.de> wrote:

> Dear Lei Wen,
>
> > On Thu, Sep 6, 2012 at 6:49 PM, Marek Vasut <marex at denx.de> wrote:
> > > Dear Lukasz Majewski,
> > >
> > > [...]
> > >
> > > > > Ok, that means we can make use of this command ?
> > > >
> > > > I cannot promise, that I will provide the "zip" support straightaway
> in
> > > > the DFU.
> > > >
> > > > On the one hand if DFU is the only user of this command we are adding
> > > > in fact a "dead" code.
> > > > On the other hand we can use proper #define CONFIG_CMD_ZIP to not
> > > > compile it until we "really" use this.
> > >
> > > I'd rather see a user and code added, not the other way.
> >
> > common/cmd_zip.c is another user. :)
>
> I'm OK with this one.
>
Nice to hear that.


>
> > And file systems could use the zip callback to directly create the zipped
> > file.
>
> Definitelly not ... zip callback for FS is wrong.
>

If there is another work around that facilitate write compressed memory into
fs, I also like to take it. Certainly callback is not the only choice.


> > Since current ext4 and fat in uboot support write function, I think it
> > could be
> > a potential feature to add.
>
> cmd_zip + fs write call is OK. But why do we need to zip anything in uboot,
> what's the usecase?
>

The use case may come from we need to dump a range of board memory.
While this range tend to be large, and this dump operation behavior may
occur frequently. Then do compression would be a good choice.

It would allow us to do more dump than the non-compression one.


>
>
> > > > Are there any other potential "users" of this functionality (ZIP
> > > > compression/decompression) in u-boot?
> > >
> > > None that I know of. Is it really zip or is it gzip ?
> >
> > It is porting from zlib, and is there any different for the compression
> > side for
> > zip and gzip?
>
> I ain't no expert, so I'm asking
>

I quote below saying from zlib.net, maybe this could make us understand the
difference. :)
"Mark is also the author of gzip's
andUnZip<http://www.info-zip.org/pub/infozip/UnZip.html>'s
main decompression routines and was the original author of Zip. Not
surprisingly, the compression algorithm used in zlib is essentially the
same as that in gzip and Zip, namely, the `deflate' method that originated
in PKWARE <http://www.pkware.com/>'s PKZIP 2.x."

Thanks,
Lei