[PATCH 3.16 032/132] hwmon: (w83627hf) Use request_muxed_region for Super-IO accesses

[Ben Hutchings]

3.16.74-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Guenter Roeck <linux@xxxxxxxxxxxx>

commit e95fd518d05bfc087da6fcdea4900a57cfb083bd upstream.

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: b72656dbc491 ("hwmon: (w83627hf) Stop using globals for I/O port numbers")
Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 drivers/hwmon/w83627hf.c | 42 +++++++++++++++++++++++++++++++++++-----
 1 file changed, 37 insertions(+), 5 deletions(-)

--- a/drivers/hwmon/w83627hf.c
+++ b/drivers/hwmon/w83627hf.c
@@ -130,17 +130,23 @@ superio_select(struct w83627hf_sio_data
 	outb(ld,  sio->sioaddr + 1);
 }
 
-static inline void
+static inline int
 superio_enter(struct w83627hf_sio_data *sio)
 {
+	if (!request_muxed_region(sio->sioaddr, 2, DRVNAME))
+		return -EBUSY;
+
 	outb(0x87, sio->sioaddr);
 	outb(0x87, sio->sioaddr);
+
+	return 0;
 }
 
 static inline void
 superio_exit(struct w83627hf_sio_data *sio)
 {
 	outb(0xAA, sio->sioaddr);
+	release_region(sio->sioaddr, 2);
 }
 
 #define W627_DEVID 0x52
@@ -1273,7 +1279,7 @@ static DEVICE_ATTR(name, S_IRUGO, show_n
 static int __init w83627hf_find(int sioaddr, unsigned short *addr,
 				struct w83627hf_sio_data *sio_data)
 {
-	int err = -ENODEV;
+	int err;
 	u16 val;
 
 	static __initconst char *const names[] = {
@@ -1285,7 +1291,11 @@ static int __init w83627hf_find(int sioa
 	};
 
 	sio_data->sioaddr = sioaddr;
-	superio_enter(sio_data);
+	err = superio_enter(sio_data);
+	if (err)
+		return err;
+
+	err = -ENODEV;
 	val = force_id ? force_id : superio_inb(sio_data, DEVID);
 	switch (val) {
 	case W627_DEVID:
@@ -1639,9 +1649,21 @@ static int w83627thf_read_gpio5(struct p
 	struct w83627hf_sio_data *sio_data = dev_get_platdata(&pdev->dev);
 	int res = 0xff, sel;
 
-	superio_enter(sio_data);
+	if (superio_enter(sio_data)) {
+		/*
+		 * Some other driver reserved the address space for itself.
+		 * We don't want to fail driver instantiation because of that,
+		 * so display a warning and keep going.
+		 */
+		dev_warn(&pdev->dev,
+			 "Can not read VID data: Failed to enable SuperIO access\n");
+		return res;
+	}
+
 	superio_select(sio_data, W83627HF_LD_GPIO5);
 
+	res = 0xff;
+
 	/* Make sure these GPIO pins are enabled */
 	if (!(superio_inb(sio_data, W83627THF_GPIO5_EN) & (1<<3))) {
 		dev_dbg(&pdev->dev, "GPIO5 disabled, no VID function\n");
@@ -1672,7 +1694,17 @@ static int w83687thf_read_vid(struct pla
 	struct w83627hf_sio_data *sio_data = dev_get_platdata(&pdev->dev);
 	int res = 0xff;
 
-	superio_enter(sio_data);
+	if (superio_enter(sio_data)) {
+		/*
+		 * Some other driver reserved the address space for itself.
+		 * We don't want to fail driver instantiation because of that,
+		 * so display a warning and keep going.
+		 */
+		dev_warn(&pdev->dev,
+			 "Can not read VID data: Failed to enable SuperIO access\n");
+		return res;
+	}
+
 	superio_select(sio_data, W83627HF_LD_HWM);
 
 	/* Make sure these GPIO pins are enabled */