2 files changed, 27 insertions, 2 deletions

diff --git a/Documentation/i2c/busses/i2c-i801 b/Documentation/i2c/busses/i2c-i801
index e1bb5b261693..e307914a3eda 100644
--- a/Documentation/i2c/busses/i2c-i801
+++ b/Documentation/i2c/busses/i2c-i801
@@ -27,7 +27,13 @@ Authors:
 Module Parameters
 -----------------
 
-None.
+* disable_features (bit vector)
+Disable selected features normally supported by the device. This makes it
+possible to work around possible driver or hardware bugs if the feature in
+question doesn't work as intended for whatever reason. Bit values:
+  1  disable SMBus PEC
+  2  disable the block buffer
+  8  disable the I2C block read functionality
 
 
 Description
diff --git a/drivers/i2c/busses/i2c-i801.c b/drivers/i2c/busses/i2c-i801.c
index 299b918455a3..f0fef343e19b 100644
--- a/drivers/i2c/busses/i2c-i801.c
+++ b/drivers/i2c/busses/i2c-i801.c
@@ -138,6 +138,17 @@ static struct pci_dev *I801_dev;
 #define FEATURE_I2C_BLOCK_READ  (1 << 3)
 static unsigned int i801_features;
 
+static const char *i801_feature_names[] = {
+        "SMBus PEC",
+        "Block buffer",
+        "Block process call",
+        "I2C block read",
+};
+
+static unsigned int disable_features;
+module_param(disable_features, uint, S_IRUGO | S_IWUSR);
+MODULE_PARM_DESC(disable_features, "Disable selected driver features");
+
 /* Make sure the SMBus host is ready to start transmitting.
    Return 0 if it is, -EBUSY if it is not. */
 static int i801_check_pre(void)
@@ -692,7 +703,7 @@ static void __devinit dmi_check_onboard_devices(const struct dmi_header *dm,
 static int __devinit i801_probe(struct pci_dev *dev, const struct pci_device_id *id)
 {
         unsigned char temp;
-        int err;
+        int err, i;
 #if defined CONFIG_SENSORS_FSCHMD || defined CONFIG_SENSORS_FSCHMD_MODULE
         const char *vendor;
 #endif
@@ -720,6 +731,14 @@ static int __devinit i801_probe(struct pci_dev *dev, const struct pci_device_id
                 break;
         }
 
+        /* Disable features on user request */
+        for (i = 0; i < ARRAY_SIZE(i801_feature_names); i++) {
+                if (i801_features & disable_features & (1 << i))
+                        dev_notice(&dev->dev, "%s disabled by user\n",
+                                   i801_feature_names[i]);
+        }
+        i801_features &= ~disable_features;
+
         err = pci_enable_device(dev);
         if (err) {
                 dev_err(&dev->dev, "Failed to enable SMBus PCI device (%d)\n",