[coreboot] SeaBIOS, serial output, and grub

Kevin O'Connor kevin at koconnor.net
Sat May 16 04:37:56 CEST 2009


On Fri, May 15, 2009 at 11:27:35AM -0400, Ward Vandewege wrote:
> Now - the reason why I wanted to use sgabios, was to get the seabios console
> output on serial.
> 
> As you can see in the logs, sgabios is loaded too late to be much use for
> that (after the disk detection, and after seabios prints 'Press F12 for boot
> menu').
> 
> If sgabios is the way to get seabios to copy console to serial, would it be
> possible to load the sgabios option rom (much) earlier?

Sgabios isn't a PnP rom, and it therefore doesn't get called before
the boot menu.  You can try the patch to sgabios below - I don't know
how reliable it will be.

Nathan - BTW, it looks like sgabios is modifying itself - that's fine,
but it will need to update its checksum before returning to the bios.

-Kevin


--- sgabios.S   (revision 4)
+++ sgabios.S   (working copy)
@@ -125,7 +125,7 @@
        /* FIXME: **** PnP header currently disabled by PoO **** */
        /* legacy entry only called once, PnP entry called multiple times */
        /* The code isn't yet written to deal with multiple inits properly */
-       .ascii "$PoO"           /* PnP expansion header signature */
+       .ascii "$PnP"           /* PnP expansion header signature */
        .byte 1                 /* structure revision */
        .byte 2                 /* length in 16-byte increments */
        .word 0                 /* offset of next header, 0 if none */
@@ -138,7 +138,7 @@
        .byte 0xe3              /* device indicators, input/display dev */
        .word 0                 /* boot connection vector, 0 if none */
        .word 0                 /* disconnect vector, 0 if none */
-       .word pnp_init          /* bootstrap entry vector */
+       .word 0                 /* bootstrap entry vector */
        .word 0                 /* reserved */
        .word 0                 /* static resource information vector */




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