[PATCH 2/3] Kbuild: Implement CONFIG_UIMAGE_KERNEL_NOLOAD

On Wed, 7 Mar 2012, Stephen Warren wrote:

On 03/07/2012 11:36 AM, Jean-Christophe PLAGNIOL-VILLARD wrote:

quoted

On 11:40 Wed 07 Mar     , Stephen Warren wrote:

quoted

On 03/07/2012 11:08 AM, Jean-Christophe PLAGNIOL-VILLARD wrote:

quoted

On 17:30 Tue 06 Mar     , Stephen Warren wrote:

quoted

This allows the user to use U-Boot's mkimage's -T kernel_noload option
if their arch Kconfig allows it, and they desire.

Signed-off-by: Stephen Warren <redacted>
---
The next patch enables this new CONFIG_ALLOW_ option for ARM. I assume
that some other architectures will also be able to enable it, but I'm
not familiar enough with any to know which.

I'm going to repeat. I don't think any impromevent here.

with no specific kernel load address the uImage for is useless/

No, the whole point of this type of kernel image is that it doesn't need
a specific load address; the kernel zImage can run from anywhere in RAM
(provided AUTO_ZRELADDR is enabled, subject to some slight
restrictions), and hence the uImage doesn't need to be loaded to or
moved to any particular location.

The scripts that U-Boot runs determine where the image gets loaded into
memory.

so instead of spending time on the uImage add simply the support the zImage to
U-Boot as this AUTO_ZRELADDR have 0 advantage compare to the zImage

Thinking more about this, I guess the reliance on AUTO_ZRELADDR is wrong
here; Russell, Nico, is the ARM decompressor fully position-independent
irrespective of the AUTO_ZRELADDR setting.

Absolutely.

That setting just determines where the decompressor writes its output, 
not what address the decompressor can run at, right?

Right.

So, this KERNEL_NOLOAD feature could be
enabled in all cases on ARM, not only when AUTO_ZRELADDR is enabled.

Except when CONFIG_ZBOOT_ROM is selected (if the uImage format 
allows it), or when the u-Boot environment doesn't know where to load 
the uImage.

FWIW, I really hate this confusing usage of "noload" imposed on us by
we know who.  I thought better than contesting his definition though.

But yes, AUTO_ZRELADDR has no effect on the location where the zImage 
should be _loaded_, except for the 128MB restriction.

As such to address Jean-Christophe's most recent comment above, this
patch isn't about adding support for AUTO_ZRELADDR, but for U-Boot's
kernel_noload feature, so comparisons should be drawn between
kernel_noload uImages and zImage, not between AUTO_ZRELADDR and zImage.

In other words:

We already have and need ZRELADDR no matter what, for reasons unrelated
to U-Boot/uImage.

Well, I do have a patch series getting rid of ZRELADDR entirely, and 
AUTO_ZRELADDR would then become implicit, unless CONFIG_PHYS_OFFSET is 
defined.


Nicolas