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@xxxxxxxxxx> Reported-by: John Garry <john.garry@xxxxxxxxxx> Cc: John Garry <john.garry@xxxxxxxxxx> Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx> --- drivers/hwmon/smsc47b397.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/drivers/hwmon/smsc47b397.c b/drivers/hwmon/smsc47b397.c index c0775084dde0..60e193f2e970 100644 --- 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 @@ -300,8 +305,12 @@ 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) { -- 2.7.4