[PATCH] I2C: restore correct vaio handling in eeprom driver

Here is a patch to the eeprom driver in 2.6.1 that changes the way Vaio
eeproms are handled. In 2.6.1, the eeprom is readable only by root,
which isn't consistent with the 2.4 driver which simple hides (i.e.
fills it with zeroes) the first row (16 bytes) of the eeprom to regular
users.

The patch restores a similar behaviour in the 2.6 driver.

drivers/i2c/chips/eeprom.c

@@ -27,6 +27,7 @@
 #include <linux/init.h>
 #include <linux/module.h>
 #include <linux/slab.h>
+#include <linux/sched.h>
 #include <linux/i2c.h>
 #include <linux/i2c-sensor.h>
 
@@ -62,6 +63,7 @@ struct eeprom_data {
 	char valid;			/* !=0 if following fields are valid */
 	unsigned long last_updated;	/* In jiffies */
 	u8 data[EEPROM_SIZE];		/* Register values */
+	enum eeprom_nature nature;
 };
 
 
@@ -127,7 +129,16 @@ static ssize_t eeprom_read(struct kobject *kobj, char *buf, loff_t off, size_t c
 	if (off + count > EEPROM_SIZE)
 		count = EEPROM_SIZE - off;
 
-	memcpy(buf, &data->data[off], count);
+	/* Hide Vaio security settings to regular users (16 first bytes) */
+	if (data->nature == VAIO && off < 16 && !capable(CAP_SYS_ADMIN)) {
+		int in_row1 = 16 - off;
+		memset(buf, 0, in_row1);
+		if (count - in_row1 > 0)
+			memcpy(buf + in_row1, &data->data[16], count - in_row1);
+	} else {
+		memcpy(buf, &data->data[off], count);
+	}
+
 	return count;
 }
 
@@ -151,7 +162,6 @@ int eeprom_detect(struct i2c_adapter *adapter, int address, int kind)
 	int i, cs;
 	struct i2c_client *new_client;
 	struct eeprom_data *data;
-	enum eeprom_nature nature = UNKNOWN;
 	int err = 0;
 
 	/* Make sure we aren't probing the ISA bus!! This is just a safety check
@@ -199,6 +209,7 @@ int eeprom_detect(struct i2c_adapter *adapter, int address, int kind)
 			goto exit_kfree;
 	}
 
+	data->nature = UNKNOWN;
 	/* Detect the Vaio nature of EEPROMs.
 	   We use the "PCG-" prefix as the signature. */
 	if (address == 0x57) {
@@ -206,17 +217,7 @@ int eeprom_detect(struct i2c_adapter *adapter, int address, int kind)
 		    i2c_smbus_read_byte_data(new_client, 0x81) == 'C' && 
 		    i2c_smbus_read_byte_data(new_client, 0x82) == 'G' &&
 		    i2c_smbus_read_byte_data(new_client, 0x83) == '-')
-			nature = VAIO;
-	}
-
-	/* If this is a VIAO, then we only allow root to read from this file,
-	   as BIOS passwords can be present here in plaintext */
-	switch (nature) {
- 	case VAIO:
-		eeprom_attr.attr.mode = S_IRUSR;
-		break;
-	default:
-		eeprom_attr.attr.mode = S_IRUGO;
+			data->nature = VAIO;
 	}
 
 	/* Fill in the remaining client fields */