[PATCH 2/4] hwmon: (pc87427) Use request_muxed_region for Super-IO accesses

[Guenter Roeck <linux@roeck-us.net>]

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: ba224e2c4f0a7 ("hwmon: New PC87427 hardware monitoring driver")
Reported-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Reported-by: John Garry <john.garry@huawei.com>
Cc: John Garry <john.garry@huawei.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
 drivers/hwmon/pc87427.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/drivers/hwmon/pc87427.c b/drivers/hwmon/pc87427.c
index d1a3f2040c00..58eee8fa3e6d 100644
--- a/drivers/hwmon/pc87427.c
+++ b/drivers/hwmon/pc87427.c
@@ -106,6 +106,13 @@ static const char *logdev_str[2] = { DRVNAME " FMC", DRVNAME " HMC" };
 #define LD_IN		1
 #define LD_TEMP		1
 
+static inline int superio_enter(int sioaddr)
+{
+	if (!request_muxed_region(sioaddr, 2, DRVNAME))
+		return -EBUSY;
+	return 0;
+}
+
 static inline void superio_outb(int sioaddr, int reg, int val)
 {
 	outb(reg, sioaddr);
@@ -122,6 +129,7 @@ static inline void superio_exit(int sioaddr)
 {
 	outb(0x02, sioaddr);
 	outb(0x02, sioaddr + 1);
+	release_region(sioaddr, 2);
 }
 
 /*
@@ -1195,7 +1203,11 @@ static int __init pc87427_find(int sioaddr, struct pc87427_sio_data *sio_data)
 {
 	u16 val;
 	u8 cfg, cfg_b;
-	int i, err = 0;
+	int i, err;
+
+	err = superio_enter(sioaddr);
+	if (err)
+		return err;
 
 	/* Identify device */
 	val = force_id ? force_id : superio_inb(sioaddr, SIOREG_DEVID);
-- 
2.7.4