hwmon: (smsc47m1) Use request_muxed_region for Super-IO accesses

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@huawei.com>
Reported-by: John Garry <john.garry@huawei.com>
Cc: John Garry <john.garry@huawei.com>
Acked-by: John Garry <john.garry@huawei.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

diff --git a/drivers/hwmon/smsc47m1.c b/drivers/hwmon/smsc47m1.c
index 5d0c6eaae6f292136db28cc200fde4bf8ecd6f46..5f92eab24c628582e7bf7622d92e24ddf05e8886 100644 (file)
--- a/drivers/hwmon/smsc47m1.c
+++ b/drivers/hwmon/smsc47m1.c
@@ -73,16 +73,21 @@ superio_inb(int reg)
 /* logical device for fans is 0x0A */
 #define superio_select() superio_outb(0x07, 0x0A)
 
-static inline 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_ACT                0x30
@@ -535,8 +540,12 @@ static int __init smsc47m1_find(struct smsc47m1_sio_data *sio_data)
 {
        u8 val;
        unsigned short addr;
+       int err;
+
+       err = superio_enter();
+       if (err)
+               return err;
 
-       superio_enter();
        val = force_id ? force_id : superio_inb(SUPERIO_REG_DEVID);
 
        /*
@@ -612,13 +621,14 @@ static int __init smsc47m1_find(struct smsc47m1_sio_data *sio_data)
 static void smsc47m1_restore(const struct smsc47m1_sio_data *sio_data)
 {
        if ((sio_data->activate & 0x01) == 0) {
-               superio_enter();
-               superio_select();
-
-               pr_info("Disabling device\n");
-               superio_outb(SUPERIO_REG_ACT, sio_data->activate);
-
-               superio_exit();
+               if (!superio_enter()) {
+                       superio_select();
+                       pr_info("Disabling device\n");
+                       superio_outb(SUPERIO_REG_ACT, sio_data->activate);
+                       superio_exit();
+               } else {
+                       pr_warn("Failed to disable device\n");
+               }
        }
 }