[microblaze-uclinux] Note to bootloader developers

[John Williams <jwilliams@xxxxxxxxxxxxxx>]

Hi folks,

The wishlist is proving succesfull, at least in the bootloader 
department, with two excellent and, in some senses complementary, 
solutions being offered recently.

A note to the developers of these bootloaders, if you wish to add kernel 
command line support, it's easy.  When you jump to the kernel start 
address, just have r5 contain the address of a null-terminated string 
that is the kernel command line.  This string could live anywhere - 
BRAM, flash, doesn't matter. The kernel copies it away safely very early 
in the piece, so you don't need to worry about it getting corrupted.

Also, if your bootloader is written in C, it's even easier than that:

from the existing JBoot loader:

char cmdline[512]

// take an argument for the cmdline buffer
typedef void (*void_fn)(void *);
void_fn kernel_start;

...

kernel_start = (void_fn)ddr_start;  /* Kernel image address */
kernel_start(cmdline);          /* Never returns */

Regards,

John

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