Re: [PATCH] The VIA Hardware RNG driver is for the CPU, not Chipset

[Arjan Koers <4kgluc2fa5qp@list.nospam.xutrox.com>]

Harald Welte wrote:
> This is a cosmetic change, fixing the MODULE_DESCRIPTION() of via-rng.c

Coincidentally, I was trying to make my RNG work for x86_64 today and I
was wondering about this. How can multiple RNGs in current dual-processor
setups and in the future multicore Nano be handled?


The MSR wizardry in via_rng_init doesn't seem to work on my Nano. I'm
simply skipping it with the patch below, because my RNG is enabled
by default. I don't know the proper way to initialize it because of
lacking documentation. Would you happen to know a better way of doing
this?

diff -u linux-2.6.30-rc5.orig/drivers/char/hw_random/Kconfig linux-2.6.30-rc5/drivers/char/hw_random/Kconfig
--- linux-2.6.30-rc5.orig/drivers/char/hw_random/Kconfig	2009-04-23 20:13:55.000000000 +0000
+++ linux-2.6.30-rc5/drivers/char/hw_random/Kconfig	2009-05-10 09:59:59.000000000 +0000
@@ -88,7 +88,7 @@

 config HW_RANDOM_VIA
 	tristate "VIA HW Random Number Generator support"
-	depends on HW_RANDOM && X86_32
+	depends on HW_RANDOM && X86
 	default HW_RANDOM
 	---help---
 	  This driver provides kernel-side support for the Random Number
diff -u linux-2.6.30-rc5.orig/drivers/char/hw_random/via-rng.c linux-2.6.30-rc5/drivers/char/hw_random/via-rng.c
--- linux-2.6.30-rc5.orig/drivers/char/hw_random/via-rng.c	2009-03-23 23:12:14.000000000 +0000
+++ linux-2.6.30-rc5/drivers/char/hw_random/via-rng.c	2009-05-10 15:33:23.000000000 +0000
@@ -132,6 +132,17 @@
 	struct cpuinfo_x86 *c = &cpu_data(0);
 	u32 lo, hi, old_lo;

+	/* Nano */
+	if ((c->x86 == 6) && (c->x86_model >= 0xf)) {
+		if (!cpu_has_xstore_enabled) {
+			printk(KERN_ERR PFX
+			       "don't know how to enable VIA Nano RNG,"
+			       " aborting\n");
+			return -ENODEV;
+		}
+		return 0;
+	}
+
 	/* Control the RNG via MSR.  Tread lightly and pay very close
 	 * close attention to values written, as the reserved fields
 	 * are documented to be "undefined and unpredictable"; but it