use #S/sdctl to find a list of sd controllers to probe
for nvram or 9fat/plan9.nvr.  this allows for nvram
on any sd device without them being present in nvtab.
this allows nframe from, e.g. sdE1 (ahci) and sde0 (aoe)
and in the future, hopefully sda0 (combined mode sata/sas
controllers like the marvell orion).

Notes:

now that i've put the marvell orion combined sata/sas
Mon May 4 17:12:43 EDT 2009 geoff
    I just point nvr* in plan9.ini at the right place.


Reference: /n/sources/patch/maybe/readnvram
Date: Sat Apr  4 15:27:20 CES 2009
Signed-off-by: quanstro@quanstro.net
Reviewed-by: geoff

--- /sys/src/libauthsrv/readnvram.c	Tue Mar 24 19:16:12 2009
+++ /sys/src/libauthsrv/readnvram.c	Tue Mar 24 19:16:11 2009
@@ -25,22 +25,8 @@
 	int len;
 } nvtab[] = {
 	"sparc", "#r/nvram", 1024+850, sizeof(Nvrsafe),
-	"pc", "#S/sdC0/nvram", 0, sizeof(Nvrsafe),
-	"pc", "#S/sdC0/9fat", -1, sizeof(Nvrsafe),
-	"pc", "#S/sdC1/nvram", 0, sizeof(Nvrsafe),
-	"pc", "#S/sdC1/9fat", -1, sizeof(Nvrsafe),
-	"pc", "#S/sdD0/nvram", 0, sizeof(Nvrsafe),
-	"pc", "#S/sdD0/9fat", -1, sizeof(Nvrsafe),
-	"pc", "#S/sdE0/nvram", 0, sizeof(Nvrsafe),
-	"pc", "#S/sdE0/9fat", -1, sizeof(Nvrsafe),
-	"pc", "#S/sdF0/nvram", 0, sizeof(Nvrsafe),
-	"pc", "#S/sdF0/9fat", -1, sizeof(Nvrsafe),
-	"pc", "#S/sd00/nvram", 0, sizeof(Nvrsafe),
-	"pc", "#S/sd00/9fat", -1, sizeof(Nvrsafe),
-	"pc", "#S/sd01/nvram", 0, sizeof(Nvrsafe),
-	"pc", "#S/sd01/9fat", -1, sizeof(Nvrsafe),
-	"pc", "#S/sd10/nvram", 0, sizeof(Nvrsafe),
-	"pc", "#S/sd10/9fat", -1, sizeof(Nvrsafe),
+	"pc", "#S/%s%d/9fat", -1, 512,
+	"pc", "#S/%s%d/nvram",	0, 512,
 	"pc", "#f/fd0disk", -1, 512,	/* 512: #f requires whole sector reads */
 	"pc", "#f/fd1disk", -1, 512,
 	"mips", "#r/nvram", 1024+900, sizeof(Nvrsafe),
@@ -123,6 +109,44 @@
 	}
 }
 
+static int
+sdnvram0(char *s, int l, int tabi)
+{
+	char *p, *f[3], buf[16];
+	int fd,i;
+
+	s[l] = 0;
+	for(; p = strchr(s, '\n'); s = p + 1){
+		if(tokenize(s, f, nelem(f)) < 1)
+			continue;
+		for(i = 0; i < 10; i++){
+			snprint(buf, sizeof buf, nvtab[tabi].file, f[0], i);
+			if((fd = open(buf, ORDWR)) >= 0)
+				return fd;
+		}
+	}
+	return -1;
+}
+
+static int
+sdnvram(int tabi)
+{
+	char *s;
+	int fd, l, r;
+
+	fd = open("#S/sdctl", OREAD);
+	if(fd == -1)
+		return -1;
+	r = -1;
+	l = 1024;	/* #S/sdctl has 0 size; guess */
+	if(s = malloc(l + 1))
+	if((l = read(fd, s, l)) > 0)
+		r = sdnvram0(s, l, tabi);
+	free(s);
+	close(fd);
+	return r;
+}
+
 typedef struct {
 	int	fd;
 	int	safeoff;
@@ -185,7 +209,11 @@
 		for(i=0; i<nelem(nvtab); i++){
 			if(strcmp(cputype, nvtab[i].cputype) != 0)
 				continue;
-			if((fd = open(nvtab[i].file, ORDWR)) < 0)
+			if(nvtab[i].file[0] == '#' && nvtab[i].file[1] == 'S')
+				fd = sdnvram(i);
+			else
+				fd = open(nvtab[i].file, ORDWR);
+			if(fd < 0)
 				continue;
 			safeoff = nvtab[i].off;
 			safelen = nvtab[i].len;