eeprom: at24: split at24_eeprom_read() into specialized functions

Split at24_eeprom_read() into two smaller functions - one for the
i2c operations and one for the smbus extensions. Assign them in
at24_probe() depending on the bus capabilities.

Also: in order to avoid duplications move the comments related to
offset calculations above the at24_translate_offset() routine.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

drivers/misc/eeprom/at24.c

@@ -165,6 +165,19 @@ MODULE_DEVICE_TABLE(acpi, at24_acpi_ids);
  * This routine supports chips which consume multiple I2C addresses. It
  * computes the addressing information to be used for a given r/w request.
  * Assumes that sanity checks for offset happened at sysfs-layer.
+ *
+ * Slave address and byte offset derive from the offset. Always
+ * set the byte address; on a multi-master board, another master
+ * may have changed the chip's "current" address pointer.
+ *
+ * REVISIT some multi-address chips don't rollover page reads to
+ * the next slave address, so we may need to truncate the count.
+ * Those chips might need another quirk flag.
+ *
+ * If the real hardware used four adjacent 24c02 chips and that
+ * were misconfigured as one 24c08, that would be a similar effect:
+ * one "eeprom" file not four, but larger reads would fail when
+ * they crossed certain pages.
  */
 static struct i2c_client *at24_translate_offset(struct at24_data *at24,
 						unsigned int *offset)
@@ -182,74 +195,77 @@ static struct i2c_client *at24_translate_offset(struct at24_data *at24,
 	return at24->client[i];
 }
 
-static ssize_t at24_eeprom_read(struct at24_data *at24, char *buf,
-				unsigned int offset, size_t count)
+static ssize_t at24_eeprom_read_smbus(struct at24_data *at24, char *buf,
+				      unsigned int offset, size_t count)
 {
-	struct i2c_msg msg[2];
-	u8 msgbuf[2];
+	unsigned long timeout, read_time;
 	struct i2c_client *client;
+	int status;
+
+	client = at24_translate_offset(at24, &offset);
+
+	if (count > io_limit)
+		count = io_limit;
+
+	/* Smaller eeproms can work given some SMBus extension calls */
+	if (count > I2C_SMBUS_BLOCK_MAX)
+		count = I2C_SMBUS_BLOCK_MAX;
+
+	loop_until_timeout(timeout, read_time) {
+		status = i2c_smbus_read_i2c_block_data_or_emulated(client,
+								   offset,
+								   count, buf);
+
+		dev_dbg(&client->dev, "read %zu@%d --> %d (%ld)\n",
+				count, offset, status, jiffies);
+
+		if (status == count)
+			return count;
+	}
+
+	return -ETIMEDOUT;
+}
+
+static ssize_t at24_eeprom_read_i2c(struct at24_data *at24, char *buf,
+				    unsigned int offset, size_t count)
+{
 	unsigned long timeout, read_time;
+	struct i2c_client *client;
+	struct i2c_msg msg[2];
 	int status, i;
+	u8 msgbuf[2];
 
 	memset(msg, 0, sizeof(msg));
-
-	/*
-	 * REVISIT some multi-address chips don't rollover page reads to
-	 * the next slave address, so we may need to truncate the count.
-	 * Those chips might need another quirk flag.
-	 *
-	 * If the real hardware used four adjacent 24c02 chips and that
-	 * were misconfigured as one 24c08, that would be a similar effect:
-	 * one "eeprom" file not four, but larger reads would fail when
-	 * they crossed certain pages.
-	 */
-
-	/*
-	 * Slave address and byte offset derive from the offset. Always
-	 * set the byte address; on a multi-master board, another master
-	 * may have changed the chip's "current" address pointer.
-	 */
 	client = at24_translate_offset(at24, &offset);
 
 	if (count > io_limit)
 		count = io_limit;
 
-	if (at24->use_smbus) {
-		/* Smaller eeproms can work given some SMBus extension calls */
-		if (count > I2C_SMBUS_BLOCK_MAX)
-			count = I2C_SMBUS_BLOCK_MAX;
-	} else {
-		/*
-		 * When we have a better choice than SMBus calls, use a
-		 * combined I2C message. Write address; then read up to
-		 * io_limit data bytes. Note that read page rollover helps us
-		 * here (unlike writes). msgbuf is u8 and will cast to our
-		 * needs.
-		 */
-		i = 0;
-		if (at24->chip.flags & AT24_FLAG_ADDR16)
-			msgbuf[i++] = offset >> 8;
-		msgbuf[i++] = offset;
+	/*
+	 * When we have a better choice than SMBus calls, use a combined I2C
+	 * message. Write address; then read up to io_limit data bytes. Note
+	 * that read page rollover helps us here (unlike writes). msgbuf is
+	 * u8 and will cast to our needs.
+	 */
+	i = 0;
+	if (at24->chip.flags & AT24_FLAG_ADDR16)
+		msgbuf[i++] = offset >> 8;
+	msgbuf[i++] = offset;
 
-		msg[0].addr = client->addr;
-		msg[0].buf = msgbuf;
-		msg[0].len = i;
+	msg[0].addr = client->addr;
+	msg[0].buf = msgbuf;
+	msg[0].len = i;
 
-		msg[1].addr = client->addr;
-		msg[1].flags = I2C_M_RD;
-		msg[1].buf = buf;
-		msg[1].len = count;
-	}
+	msg[1].addr = client->addr;
+	msg[1].flags = I2C_M_RD;
+	msg[1].buf = buf;
+	msg[1].len = count;
 
 	loop_until_timeout(timeout, read_time) {
-		if (at24->use_smbus) {
-			status = i2c_smbus_read_i2c_block_data_or_emulated(client, offset,
-									   count, buf);
-		} else {
-			status = i2c_transfer(client->adapter, msg, 2);
-			if (status == 2)
-				status = count;
-		}
+		status = i2c_transfer(client->adapter, msg, 2);
+		if (status == 2)
+			status = count;
+
 		dev_dbg(&client->dev, "read %zu@%d --> %d (%ld)\n",
 				count, offset, status, jiffies);
 
@@ -520,7 +536,8 @@ static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
 	at24->chip = chip;
 	at24->num_addresses = num_addresses;
 
-	at24->read_func = at24_eeprom_read;
+	at24->read_func = at24->use_smbus ? at24_eeprom_read_smbus
+					  : at24_eeprom_read_i2c;
 	at24->write_func = at24_eeprom_write;
 
 	writable = !(chip.flags & AT24_FLAG_READONLY);