Added /dev/cputemp to BCM port. It is useful because board is often kept in a box and has no active cooling.

Reference: /n/sources/patch/maybe/bcm-cputemp
Date: Wed Dec  4 19:34:37 CET 2013
Signed-off-by: krystian.lew@gmail.com

--- /sys/src/9/bcm/devarch.c	Wed Dec  4 19:33:23 2013
+++ /sys/src/9/bcm/devarch.c	Wed Dec  4 19:33:20 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	Wed Dec  4 19:33:28 2013
+++ /sys/src/9/bcm/fns.h	Wed Dec  4 19:33:25 2013
@@ -41,6 +41,7 @@
 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	Wed Dec  4 19:33:32 2013
+++ /sys/src/9/bcm/io.h	Wed Dec  4 19:33:30 2013
@@ -42,4 +42,6 @@
 	ClkSdram,
 	ClkPixel,
 	ClkPwm,
+
+	TempDefault = 0,	/* Specification says "id should be 0" */
 };
--- /sys/src/9/bcm/vcore.c	Wed Dec  4 19:33:37 2013
+++ /sys/src/9/bcm/vcore.c	Wed Dec  4 19:33:34 2013
@@ -39,6 +39,7 @@
 	TagSetpower	= 0x00028001,
 		Powerwait	= 1<<1,
 	TagGetclkspd= 0x00030002,
+	TagGettemp	= 0x00030006,
 	TagFballoc	= 0x00040001,
 	TagFbfree	= 0x00048001,
 	TagFbblank	= 0x00040002,
@@ -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];
 }