On 09/26/2012 09:10 AM, Russell King - ARM Linux wrote:

On Wed, Sep 26, 2012 at 02:49:48PM +0000, Arnd Bergmann wrote:

quoted

Right now, a multiplatform kernel has no way of debugging the
decompressor using console output, so it's actually /smaller/
than a single-platform kernel, but also less capable.

Err, are you sure about all your details above?  You do realise when
debugging is disabled there is no debug code included anywhere in the
decompressor?

I think what you're referring to is not the debug output, but the normal
decompressor output.  (The "Decompressing Linux..." message is not
debug output.)

Let's be a little more clear about what "less capable" means - it will
be unable to report any errors that occur during the decompression.
What that means is that you'll end up with mere silence should an
error occur.

In the Tegra case, by omitting uncompress.h, we lose more than just the
"Decompressing Linux..." message; uncompress.h contains code to parse
extract the platform's debug UART ID from data set up by the boot ROM
(since we have 5 UARTs), and pass this on to debug-macro.S. Without
uncompress.h running, debug-macro.S would either have to hard-code a
single UART ID (and different boards uses different UARTs, which would
make running a single kernel image across all Tegra devices with
earlyprintk enabled impossible) *or* we'd have to port the UART ID
extraction code to debug-macro.S too, which I don't fancy very much
since that's assembly whereas uncompress.h is C.