hwmon: (pc87427) Use request_muxed_region for Super-IO accesses

BugLink: https://bugs.launchpad.net/bugs/1838700
[ Upstream commit 755a9b0f8aaa5639ba5671ca50080852babb89ce ]

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>
Acked-by: John Garry <john.garry@huawei.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/drivers/hwmon/pc87427.c b/drivers/hwmon/pc87427.c
index dc5a9d5ada516c840f73ee7f33971ec1bcdddcfc..81a05cd1a5121afd608a003abbf18dacdaf35fc9 100644 (file)
--- 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);
 }
 
 /*
@@ -1220,7 +1228,11 @@ 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);