hwmon: Let the user override the detected Super-I/O device ID

While it is possible to force SMBus-based hardware monitoring chip
drivers to drive a not officially supported device, we do not have this
possibility for Super-I/O-based drivers. That's unfortunate because
sometimes newer chips are fully compatible and just forcing the driver
to load would work. Instead of that we have to tell the users to
recompile the kernel driver, which isn't an easy task for everyone.

So, I propose that we add a module parameter to all Super-I/O based
hardware monitoring drivers, letting advanced users force the driver
to load on their machine. The user has to provide the device ID of a
supposedly compatible device. This requires looking at the source code or
a datasheet, so I am confident that users can't randomly force a driver
without knowing what they are doing. Thus this should be relatively safe.

As you can see from the code, the implementation is pretty simple and
unintrusive.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Acked-by: Hans de Goede <j.w.r.degoede@hhs.nl>
Signed-off-by: Mark M. Hoffman <mhoffman@lightlink.com>

1 files changed, 9 insertions, 2 deletions

diff --git a/drivers/hwmon/w83627ehf.c b/drivers/hwmon/w83627ehf.c
index d5aa25ce5dbd..699592855bd8 100644
--- a/drivers/hwmon/w83627ehf.c
+++ b/drivers/hwmon/w83627ehf.c
@@ -59,6 +59,10 @@ static const char * w83627ehf_device_names[] = {
         "w83627dhg",
 };
 
+static unsigned short force_id;
+module_param(force_id, ushort, 0);
+MODULE_PARM_DESC(force_id, "Override the detected device ID");
+
 #define DRVNAME "w83627ehf"
 
 /*
@@ -1445,8 +1449,11 @@ static int __init w83627ehf_find(int sioaddr, unsigned short *addr,
 
         superio_enter(sioaddr);
 
-        val = (superio_inb(sioaddr, SIO_REG_DEVID) << 8)
-            | superio_inb(sioaddr, SIO_REG_DEVID + 1);
+        if (force_id)
+                val = force_id;
+        else
+                val = (superio_inb(sioaddr, SIO_REG_DEVID) << 8)
+                    | superio_inb(sioaddr, SIO_REG_DEVID + 1);
         switch (val & SIO_ID_MASK) {
         case SIO_W83627EHF_ID:
                 sio_data->kind = w83627ehf;