linux-kernel - [PATCH 3.16 030/132] hwmon: (smsc47b397) Use request_muxed

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Message-ID: <lsq.1568989415.804297303@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>,
        "Kefeng Wang" <wangkefeng.wang@...wei.com>,
        "Guenter Roeck" <linux@...ck-us.net>,
        "John Garry" <john.garry@...wei.com>
Subject: [PATCH 3.16 030/132] hwmon: (smsc47b397) 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 8c0826756744c0ac1df600a5e4cca1a341b13101 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: 8d5d45fb1468 ("I2C: Move hwmon drivers (2/3)")
Reported-by: Kefeng Wang <wangkefeng.wang@...wei.com>
Reported-by: John Garry <john.garry@...wei.com>
Cc: John Garry <john.garry@...wei.com>
Acked-by: John Garry <john.garry@...wei.com>
Signed-off-by: Guenter Roeck <linux@...ck-us.net>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/hwmon/smsc47b397.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

--- a/drivers/hwmon/smsc47b397.c
+++ b/drivers/hwmon/smsc47b397.c
@@ -72,14 +72,19 @@ static inline void superio_select(int ld
 	superio_outb(0x07, ld);
 }
 
-static inline void superio_enter(void)
+static inline int superio_enter(void)
 {
+	if (!request_muxed_region(REG, 2, DRVNAME))
+		return -EBUSY;
+
 	outb(0x55, REG);
+	return 0;
 }
 
 static inline void superio_exit(void)
 {
 	outb(0xAA, REG);
+	release_region(REG, 2);
 }
 
 #define SUPERIO_REG_DEVID	0x20
@@ -338,8 +343,12 @@ static int __init smsc47b397_find(void)
 	u8 id, rev;
 	char *name;
 	unsigned short addr;
+	int err;
+
+	err = superio_enter();
+	if (err)
+		return err;
 
-	superio_enter();
 	id = force_id ? force_id : superio_inb(SUPERIO_REG_DEVID);
 
 	switch (id) {