[PATCH] 2/2 RFC: yaboot --bootonce (bootloader-space)

[Dustin Kirkland]

This is a not-yet-working prototype of the changes I suggest to the
second stage of yaboot to enable this bootonce capability.

This functionality should be relatively easy to accommodate, assuming
this list can help me clear up 2 items...

(1) I need to be able to access the prom_handle of the PReP boot device
in the context of the second/cfg.c functions.  Can someone specifically
show me if/how I can pass/access this information in this context?  In
the code below, I simply refer to it as prom_readblocks(disk... and
prom_writeblocks(disk...  But I haven't been able to figure out how to
populate "prom_handle disk".

(2) There exists a prom_write() function, but this function has no
callers.  I suppose this means that this function is substantially
untested?  Assuming prom_write() works, a prom_writeblocks() that
mirrors prom_readblocks() would be a very nice helper.  Anyone have any
information as to the workability of prom_write()?

Cowardly-commented-out patch follows ;-)

:-Dustin

Signed-off-by: Dustin Kirkland <dustin.kirkland at us.ibm.com>

diff -urpN yaboot.orig/include/prom.h yaboot.new/include/prom.h
--- yaboot.orig/include/prom.h	2006-09-13 18:01:49.000000000 -0500
+++ yaboot.new/include/prom.h	2006-09-18 16:44:58.000000000 -0500
@@ -53,6 +53,7 @@ int prom_write (prom_handle file, void *
 int prom_seek (prom_handle file, int pos);
 int prom_lseek (prom_handle file, unsigned long long pos);
 int prom_readblocks (prom_handle file, int blockNum, int blockCount, void *buffer);
+// int prom_writeblocks (prom_handle file, int blockNum, int blockCount, void *buffer);
 void prom_close (prom_handle file);
 int prom_getblksize (prom_handle file);
 int prom_loadmethod (prom_handle device, void* addr);
diff -urpN yaboot.orig/second/cfg.c yaboot.new/second/cfg.c
--- yaboot.orig/second/cfg.c	2006-09-13 18:01:49.000000000 -0500
+++ yaboot.new/second/cfg.c	2006-09-18 16:41:06.000000000 -0500
@@ -441,6 +441,20 @@ char *cfg_get_default (void)
      char *label;
      char *ret = cfg_get_strg_i (cf_options, "default");
 
+/*
+ *   char bootonce[512];
+ *   char zero[512];
+ *   int i;
+ *   for (i=0; i<512; i++)
+ *        bootonce[i] = zero[i] = '\000';
+ *   prom_readblocks(disk, 1600, 1, bootonce);
+ *   prom_writeblocks(disk, 1600, 1, zero);
+ *
+ *   if (bootonce)
+ *        return bootonce;
+ */
+
      if (ret)
 	  return ret;
      if (!images)
diff -urpN yaboot.orig/second/prom.c yaboot.new/second/prom.c
--- yaboot.orig/second/prom.c	2006-09-13 18:01:49.000000000 -0500
+++ yaboot.new/second/prom.c	2006-09-18 16:43:52.000000000 -0500
@@ -362,6 +362,31 @@ prom_readblocks (prom_handle dev, int bl
 #endif
 }
 
+/*
+ * int
+ * prom_writeblocks (prom_handle dev, int blockNum, int blockCount, void *buffer)
+ * {
+ *    int status;
+ *    unsigned int blksize;
+ *
+ *    blksize = prom_getblksize(dev);
+ *    if (blksize <= 1)
+ *	  blksize = 512;
+ *    status = prom_seek(dev, blockNum * blksize);
+ *    if (status != 1) {
+ *	  return 0;
+ *	  prom_printf("Can't seek to 0x%x\n", blockNum * blksize);
+ *    }
+ *
+ *    status = prom_write(dev, buffer, blockCount * blksize);
+ * //  prom_printf("prom_writeblocks, bl: %d, cnt: %d, status: %d\n",
+ * //  	blockNum, blockCount, status);
+ *
+ *    return status == (blockCount * blksize);
+ *
+ * }
+ */
+
 int
 prom_getchar ()
 {