1 files changed, 88 insertions, 2 deletions

diff --git a/drivers/hwmon/fschmd.c b/drivers/hwmon/fschmd.c
index d427ea5623f..b7c9eef0f92 100644
--- a/drivers/hwmon/fschmd.c
+++ b/drivers/hwmon/fschmd.c
@@ -41,6 +41,7 @@
 #include <linux/err.h>
 #include <linux/mutex.h>
 #include <linux/sysfs.h>
+#include <linux/dmi.h>
 
 /* Addresses to scan */
 static unsigned short normal_i2c[] = { 0x73, I2C_CLIENT_END };
@@ -210,6 +211,13 @@ struct fschmd_data {
 	u8 fan_ripple[6];	/* divider for rps */
 };
 
+/* Global variables to hold information read from special DMI tables, which are
+   available on FSC machines with an fscher or later chip. */
+static int dmi_mult[3] = { 490, 200, 100 };
+static int dmi_offset[3] = { 0, 0, 0 };
+static int dmi_vref = -1;
+
+
 /*
  * Sysfs attr show / store functions
  */
@@ -221,8 +229,13 @@ static ssize_t show_in_value(struct device *dev,
 	int index = to_sensor_dev_attr(devattr)->index;
 	struct fschmd_data *data = fschmd_update_device(dev);
 
-	return sprintf(buf, "%d\n", (data->volt[index] *
-		max_reading[index] + 128) / 255);
+	/* fscher / fschrc - 1 as data->kind is an array index, not a chips */
+	if (data->kind == (fscher - 1) || data->kind >= (fschrc - 1))
+		return sprintf(buf, "%d\n", (data->volt[index] * dmi_vref *
+			dmi_mult[index]) / 255 + dmi_offset[index]);
+	else
+		return sprintf(buf, "%d\n", (data->volt[index] *
+			max_reading[index] + 128) / 255);
 }
 
 
@@ -525,6 +538,68 @@ static struct sensor_device_attribute fschmd_fan_attr[] = {
  * Real code
  */
 
+/* DMI decode routine to read voltage scaling factors from special DMI tables,
+   which are available on FSC machines with an fscher or later chip. */
+static void fschmd_dmi_decode(const struct dmi_header *header)
+{
+	int i, mult[3] = { 0 }, offset[3] = { 0 }, vref = 0, found = 0;
+
+	/* dmi code ugliness, we get passed the address of the contents of
+	   a complete DMI record, but in the form of a dmi_header pointer, in
+	   reality this address holds header->length bytes of which the header
+	   are the first 4 bytes */
+	u8 *dmi_data = (u8 *)header;
+
+	/* We are looking for OEM-specific type 185 */
+	if (header->type != 185)
+		return;
+
+	/* we are looking for what Siemens calls "subtype" 19, the subtype
+	   is stored in byte 5 of the dmi block */
+	if (header->length < 5 || dmi_data[4] != 19)
+		return;
+
+	/* After the subtype comes 1 unknown byte and then blocks of 5 bytes,
+	   consisting of what Siemens calls an "Entity" number, followed by
+	   2 16-bit words in LSB first order */
+	for (i = 6; (i + 4) < header->length; i += 5) {
+		/* entity 1 - 3: voltage multiplier and offset */
+		if (dmi_data[i] >= 1 && dmi_data[i] <= 3) {
+			/* Our in sensors order and the DMI order differ */
+			const int shuffle[3] = { 1, 0, 2 };
+			int in = shuffle[dmi_data[i] - 1];
+
+			/* Check for twice the same entity */
+			if (found & (1 << in))
+				return;
+
+			mult[in] = dmi_data[i + 1] | (dmi_data[i + 2] << 8);
+			offset[in] = dmi_data[i + 3] | (dmi_data[i + 4] << 8);
+
+			found |= 1 << in;
+		}
+
+		/* entity 7: reference voltage */
+		if (dmi_data[i] == 7) {
+			/* Check for twice the same entity */
+			if (found & 0x08)
+				return;
+
+			vref = dmi_data[i + 1] | (dmi_data[i + 2] << 8);
+
+			found |= 0x08;
+		}
+	}
+
+	if (found == 0x0F) {
+		for (i = 0; i < 3; i++) {
+			dmi_mult[i] = mult[i] * 10;
+			dmi_offset[i] = offset[i] * 10;
+		}
+		dmi_vref = vref;
+	}
+}
+
 static int fschmd_detect(struct i2c_adapter *adapter, int address, int kind)
 {
 	struct i2c_client *client;
@@ -586,6 +661,17 @@ static int fschmd_detect(struct i2c_adapter *adapter, int address, int kind)
 		data->temp_max[2] = 50 + 128;
 	}
 
+	/* Read the special DMI table for fscher and newer chips */
+	if (kind == fscher || kind >= fschrc) {
+		dmi_walk(fschmd_dmi_decode);
+		if (dmi_vref == -1) {
+			printk(KERN_WARNING FSCHMD_NAME
+				": Couldn't get voltage scaling factors from "
+				"BIOS DMI table, using builtin defaults\n");
+			dmi_vref = 33;
+		}
+	}
+
 	/* i2c kind goes from 1-5, we want from 0-4 to address arrays */
 	data->kind = kind - 1;
 	strlcpy(client->name, client_names[data->kind], I2C_NAME_SIZE);