[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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