i2c: Bus drivers return -Errno not -1

Tighten error paths used by various i2c adapters (mostly x86) so
they return real fault/errno codes instead of a "-1" (which is
most often interpreted as "-EPERM").  Build tested, with eyeball
review.

One minor initial goal is to have adapters consistently return
the code "-ENXIO" when addressing a device doesn't get an ACK
response, at least in the probe paths where they are already
good at stifling related logspam.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Jean Delvare <khali@linux-fr.org>

drivers/i2c/busses/i2c-amd8111.c

@@ -77,7 +77,7 @@ static unsigned int amd_ec_wait_write(struct amd_smbus *smbus)
 	if (!timeout) {
 		dev_warn(&smbus->dev->dev,
 			 "Timeout while waiting for IBF to clear\n");
-		return -1;
+		return -ETIMEDOUT;
 	}
 
 	return 0;
@@ -93,7 +93,7 @@ static unsigned int amd_ec_wait_read(struct amd_smbus *smbus)
 	if (!timeout) {
 		dev_warn(&smbus->dev->dev,
 			 "Timeout while waiting for OBF to set\n");
-		return -1;
+		return -ETIMEDOUT;
 	}
 
 	return 0;
@@ -102,16 +102,21 @@ static unsigned int amd_ec_wait_read(struct amd_smbus *smbus)
 static unsigned int amd_ec_read(struct amd_smbus *smbus, unsigned char address,
 		unsigned char *data)
 {
-	if (amd_ec_wait_write(smbus))
-		return -1;
+	int status;
+
+	status = amd_ec_wait_write(smbus);
+	if (status)
+		return status;
 	outb(AMD_EC_CMD_RD, smbus->base + AMD_EC_CMD);
 
-	if (amd_ec_wait_write(smbus))
-		return -1;
+	status = amd_ec_wait_write(smbus);
+	if (status)
+		return status;
 	outb(address, smbus->base + AMD_EC_DATA);
 
-	if (amd_ec_wait_read(smbus))
-		return -1;
+	status = amd_ec_wait_read(smbus);
+	if (status)
+		return status;
 	*data = inb(smbus->base + AMD_EC_DATA);
 
 	return 0;
@@ -120,16 +125,21 @@ static unsigned int amd_ec_read(struct amd_smbus *smbus, unsigned char address,
 static unsigned int amd_ec_write(struct amd_smbus *smbus, unsigned char address,
 		unsigned char data)
 {
-	if (amd_ec_wait_write(smbus))
-		return -1;
+	int status;
+
+	status = amd_ec_wait_write(smbus);
+	if (status)
+		return status;
 	outb(AMD_EC_CMD_WR, smbus->base + AMD_EC_CMD);
 
-	if (amd_ec_wait_write(smbus))
-		return -1;
+	status = amd_ec_wait_write(smbus);
+	if (status)
+		return status;
 	outb(address, smbus->base + AMD_EC_DATA);
 
-	if (amd_ec_wait_write(smbus))
-		return -1;
+	status = amd_ec_wait_write(smbus);
+	if (status)
+		return status;
 	outb(data, smbus->base + AMD_EC_DATA);
 
 	return 0;
@@ -267,12 +277,17 @@ static s32 amd8111_access(struct i2c_adapter * adap, u16 addr,
 
 		default:
 			dev_warn(&adap->dev, "Unsupported transaction %d\n", size);
-			return -1;
+			return -EOPNOTSUPP;
 	}
 
 	amd_ec_write(smbus, AMD_SMB_ADDR, addr << 1);
 	amd_ec_write(smbus, AMD_SMB_PRTCL, protocol);
 
+	/* FIXME this discards status from ec_read(); so temp[0] will
+	 * hold stack garbage ... the rest of this routine will act
+	 * nonsensically.  Ignored ec_write() status might explain
+	 * some such failures...
+	 */
 	amd_ec_read(smbus, AMD_SMB_STS, temp + 0);
 
 	if (~temp[0] & AMD_SMB_STS_DONE) {
@@ -286,7 +301,7 @@ static s32 amd8111_access(struct i2c_adapter * adap, u16 addr,
 	}
 
 	if ((~temp[0] & AMD_SMB_STS_DONE) || (temp[0] & AMD_SMB_STS_STATUS))
-		return -1;
+		return -EIO;
 
 	if (read_write == I2C_SMBUS_WRITE)
 		return 0;