from /n/sources/patch/bcm-cputemp.  track pi's cpu temperature.
needs to be retested.

Reference: /n/atom/patch/applied2013/picputemp
Date: Sat Dec 14 13:55:15 CET 2013
Signed-off-by: quanstro@quanstro.net

--- /sys/src/9/bcm/devarch.c	Sat Dec 14 13:54:04 2013
+++ /sys/src/9/bcm/devarch.c	Sat Dec 14 13:54:04 2013
@@ -156,8 +156,17 @@
 	return readstr(offset, a, n, str);
 }
 
+static long
+cputempread(Chan*, void *a, long n, vlong offset)
+{
+	char str[128];
+	snprint(str, sizeof str, "%d±%d\n", gettemp(TempDefault) / 1000, 1);
+	return readstr(offset, a, n, str);
+}
+
 void
 archinit(void)
 {
 	addarchfile("cputype", 0444, cputyperead, nil);
+	addarchfile("cputemp", 0444, cputempread, nil); 
 }
--- /sys/src/9/bcm/fns.h	Sat Dec 14 13:54:05 2013
+++ /sys/src/9/bcm/fns.h	Sat Dec 14 13:54:06 2013
@@ -40,6 +40,7 @@
 extern uint getfirmware(void);
 extern int getpower(int);
 extern void getramsize(Confmem*);
+extern uint gettemp(int);
 extern u32int ifsrget(void);
 extern void irqenable(int, void (*)(Ureg*, void*), void*);
 #define intrenable(i, f, a, b, n) irqenable((i), (f), (a))
--- /sys/src/9/bcm/io.h	Sat Dec 14 13:54:06 2013
+++ /sys/src/9/bcm/io.h	Sat Dec 14 13:54:07 2013
@@ -42,4 +42,6 @@
 	ClkSdram,
 	ClkPixel,
 	ClkPwm,
+
+	TempDefault = 0,	/* Specification says "id should be 0" */
 };
--- /sys/src/9/bcm/vcore.c	Sat Dec 14 13:54:08 2013
+++ /sys/src/9/bcm/vcore.c	Sat Dec 14 13:54:08 2013
@@ -39,6 +39,7 @@
 	TagSetpower	= 0x00028001,
 		Powerwait	= 1<<1,
 	TagGetclkspd= 0x00030002,
+	TagGettemp	= 0x00030006,
 	TagFballoc	= 0x00040001,
 	TagFbfree	= 0x00048001,
 	TagFbblank	= 0x00040002,
@@ -111,10 +112,10 @@
 static int
 vcreq(int tag, void *buf, int vallen, int rsplen)
 {
-	static uintptr base = BUSDRAM;
-	Prophdr *prop;
 	uintptr r;
 	int n;
+	Prophdr *prop;
+	static uintptr base = BUSDRAM;
 
 	if(rsplen < vallen)
 		rsplen = vallen;
@@ -142,7 +143,7 @@
 	if(prop->req == RspOk &&
 	   prop->tag == tag &&
 	   (prop->taglen&TagResp)) {
-		if((n = prop->taglen&~TagResp) < rsplen)
+		if((n = prop->taglen & ~TagResp) < rsplen)
 			rsplen = n;
 		memmove(buf, prop->data, rsplen);
 	}else
@@ -225,7 +226,7 @@
 
 	buf[0] = dev;
 	buf[1] = 0;
-	if(vcreq(TagGetpower, buf, sizeof(buf[0]), sizeof buf) != sizeof buf)
+	if(vcreq(TagGetpower, buf, sizeof buf[0], sizeof buf) != sizeof buf)
 		return -1;
 	return buf[0] & 1;
 }
@@ -238,9 +239,9 @@
 getethermac(void)
 {
 	uchar ea[8];
-	static char buf[16];
 	char *p;
 	int i;
+	static char buf[16];
 
 	memset(ea, 0, sizeof ea);
 	vcreq(TagGetmac, ea, 0, sizeof ea);
@@ -288,5 +289,19 @@
 	buf[0] = clkid;
 	if(vcreq(TagGetclkspd, buf, sizeof(buf[0]), sizeof(buf)) != sizeof buf)
 		return 0;
+	return buf[1];
+}
+
+/*
+* Get temperature
+*/
+uint
+gettemp(int tempid)
+{
+	u32int buf[2];
+	buf[0] = tempid;
+	if(vcreq(TagGettemp, buf, sizeof(buf[0]), sizeof(buf)) != sizeof buf)
+		return 0;
+
 	return buf[1];
 }