Re: [RFC] New target 'cuImage' - compatibility uImage

In message <1154618945.5094.6.camel@localhost> you wrote:

quoted

In my understanding, an "uImage" file is a  image  consisting  of  an
U-Boot  header (64 bytes) followed by an (compressed or uncompressed)
Linux kernel image.

Yes

OK.

I mean that the data contained within the uImage is compressed. In this

This is only one option. Some configurations  prefer  to  use  uncom-
pressed images because these canbe booted faster.

case where the uImage data is compressed I choose to skip compressing
the kernel section in the zImage (because have it compressed twice was
wasteful)

We don't use zImage !

So to clarify. The current method has a zImage with a compressed kernel

No, it does not. We do  not  use  zImage  (which  includes  bootstrap
wrapper  code).  U-Boot  uses  a plain stripped and compressed kernel
image, i. e. something like this:

	objcopy  -O binary vmlinux vmlinux.bin
	gzip -f -9 <vmlinux.bin >vmlinux.gz
	mkimage ... -C gzip -d vmlinux.gz uImage

section where the actual kernel lives. The zImage uncompressed this code
to the kernel load address. The 'cuImage' would be packaged in a uImage
with the entire zImage compressed, except in this case the kernel
section would not be compressed (to avoid have a compressed image within
a compressed image)

You would have to create a new image type which has  executable  code
at the start and carries the kernel image as payload, similar to what
zImage does. 

Best regards,

Wolfgang Denk

-- 
Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd@denx.de
The shortest unit of time in the multiverse is the News York  Second,
defined  as  the  period  of  time between the traffic lights turning
green and the cab behind you honking.
                                - Terry Pratchett, _Lords and Ladies_

On Thu, 2006-08-03 at 22:00 +0200, Wolfgang Denk wrote:

quoted

So to clarify. The current method has a zImage with a compressed

kernel

No, it does not. We do  not  use  zImage  (which  includes  bootstrap
wrapper  code).  U-Boot  uses  a plain stripped and compressed kernel
image, i. e. something like this:

        objcopy  -O binary vmlinux vmlinux.bin
        gzip -f -9 <vmlinux.bin >vmlinux.gz
        mkimage ... -C gzip -d vmlinux.gz uImage 

I'm referring to the zImage target as what the current method does. My
changes would in no way effect the current method of booting, with the
current method being a plain uImage target.

The zImage can have a compressed kernel section or an uncompressed
kernel section. The new 'cuImage' always has an uncompressed kernel
section and which is packaged in the U-Boot image format.

You might refer to the code in my original email for clarification. This
in no way effects the current method of booting, it simply adds a method
to package the bootwrapper + kernel + fdt to pass to old version of
U-Boot so they can use the new 'powerpc' kernels

As a side note, the final cuImage (which is a U-Boot image) can be
either compressed or uncompressed. That is irrelevant. The major point
is the kernel section within the cuImage is not compressed, and the
final cuImage is in fact a U-Boot image which can be started with the
'bootm' command from within U-Boot.

Phew!

-Matthew