linux-kernel - [PATCH 3.16 033/132] hwmon: (vt1211) Use request_muxed

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Message-ID: <lsq.1568989415.800348046@decadent.org.uk>
Date:   Fri, 20 Sep 2019 15:23:35 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Guenter Roeck" <linux@...ck-us.net>
Subject: [PATCH 3.16 033/132] hwmon: (vt1211) Use request_muxed_region for
 Super-IO accesses

3.16.74-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Guenter Roeck <linux@...ck-us.net>

commit 14b97ba5c20056102b3dd22696bf17b057e60976 upstream.

Super-IO accesses may fail on a system with no or unmapped LPC bus.

Also, other drivers may attempt to access the LPC bus at the same time,
resulting in undefined behavior.

Use request_muxed_region() to ensure that IO access on the requested
address space is supported, and to ensure that access by multiple drivers
is synchronized.

Fixes: 2219cd81a6cd ("hwmon/vt1211: Add probing of alternate config index port")
Signed-off-by: Guenter Roeck <linux@...ck-us.net>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/hwmon/vt1211.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

--- a/drivers/hwmon/vt1211.c
+++ b/drivers/hwmon/vt1211.c
@@ -226,15 +226,21 @@ static inline void superio_select(int si
 	outb(ldn, sio_cip + 1);
 }
 
-static inline void superio_enter(int sio_cip)
+static inline int superio_enter(int sio_cip)
 {
+	if (!request_muxed_region(sio_cip, 2, DRVNAME))
+		return -EBUSY;
+
 	outb(0x87, sio_cip);
 	outb(0x87, sio_cip);
+
+	return 0;
 }
 
 static inline void superio_exit(int sio_cip)
 {
 	outb(0xaa, sio_cip);
+	release_region(sio_cip, 2);
 }
 
 /* ---------------------------------------------------------------------
@@ -1280,11 +1286,14 @@ EXIT:
 
 static int __init vt1211_find(int sio_cip, unsigned short *address)
 {
-	int err = -ENODEV;
+	int err;
 	int devid;
 
-	superio_enter(sio_cip);
+	err = superio_enter(sio_cip);
+	if (err)
+		return err;
 
+	err = -ENODEV;
 	devid = force_id ? force_id : superio_inb(sio_cip, SIO_VT1211_DEVID);
 	if (devid != SIO_VT1211_ID)
 		goto EXIT;