[RFE] Netboot of images bigger than 6Mb

[Luis Machado]

Hi folks,

This is my first post to the yaboot-devel mailing list.

I've been using netboot with POWER machines for a while now and also
have been struggling with the problem of having images bigger than 6Mb.

As a workaround, i decided to change yaboot a bit to make it download
the images in a buffer up high in memory, above 40Mb. In this case we
most probably would have a rather large block of free memory, making it
possible to download the images. Also it would prevent us from hitting
OF.

Since the kernel+ramdisk would be too big to fit in the memory area
below 40Mb, probably hitting OF, we load the kernel high in memory also.

Today the kernel is being loaded at 20Mb. I changed that to 40Mb.

I've conducted tests with this configuration on P505's, OpenPower's,
JS20's, JS21's and Intellistation machines and they all have worked
fine.

I would need to test these modifications on Apple hardware as well.

Summary of changes:

Makefile:
- KERNELADDR  = 0x01400000
+ KERNELADDR  = 0x02800000

Load the kernel+ramdisk higher in memory, here we try 40Mb.

second/fs_oc.c
- #define LOAD_BUFFER_POS     0x600000
+ #define LOAD_BUFFER_POS     <new_value>

- #define LOAD_BUFFER_SIZE    0x600000
+ #define LOAD_BUFFER_SIZE    <new_value>

Change the download buffer size and buffer position in memory. The
buffer size could by calculated dynamically based on the amount of data
that has been downloaded or set to the limit of available memory above
the position we have chosen. I believe the limit is 128Mb.

What do you think of this solution? Comments and suggestions are
welcome.

Best regards,
Luis