ipmi: Fix multi-part message handling

Lots of little fixes for multi-part messages:

The values was not being re-initialized, if something went wrong
handling a multi-part message and it got left in a bad state, it
might be an issue.

The commands were not correct when issuing multi-part reads, the
code was not passing in the proper value for commands.  Also clean
up some minor formatting issues.

Get the block number from the right location, limit the maximum send
message size to 63 bytes and explain why, and fix some minor sylistic
issues.

Signed-off-by: Corey Minyard <cminyard@mvista.com>

drivers/char/ipmi/ipmi_ssif.c

@@ -489,13 +489,13 @@ static int ipmi_ssif_thread(void *data)
 
 		if (ssif_info->i2c_read_write == I2C_SMBUS_WRITE) {
 			result = i2c_smbus_write_block_data(
-				ssif_info->client, SSIF_IPMI_REQUEST,
+				ssif_info->client, ssif_info->i2c_command,
 				ssif_info->i2c_data[0],
 				ssif_info->i2c_data + 1);
 			ssif_info->done_handler(ssif_info, result, NULL, 0);
 		} else {
 			result = i2c_smbus_read_block_data(
-				ssif_info->client, SSIF_IPMI_RESPONSE,
+				ssif_info->client, ssif_info->i2c_command,
 				ssif_info->i2c_data);
 			if (result < 0)
 				ssif_info->done_handler(ssif_info, result,
@@ -534,6 +534,7 @@ static void start_get(struct ssif_info *ssif_info)
 	int rv;
 
 	ssif_info->rtc_us_timer = 0;
+	ssif_info->multi_pos = 0;
 
 	rv = ssif_i2c_send(ssif_info, msg_done_handler, I2C_SMBUS_READ,
 			  SSIF_IPMI_RESPONSE,
@@ -631,9 +632,9 @@ static void msg_done_handler(struct ssif_info *ssif_info, int result,
 		ssif_inc_stat(ssif_info, received_message_parts);
 
 		/* Remove the multi-part read marker. */
-		for (i = 0; i < (len-2); i++)
-			ssif_info->data[i] = data[i+2];
 		len -= 2;
+		for (i = 0; i < len; i++)
+			ssif_info->data[i] = data[i+2];
 		ssif_info->multi_len = len;
 		ssif_info->multi_pos = 1;
 
@@ -660,9 +661,9 @@ static void msg_done_handler(struct ssif_info *ssif_info, int result,
 			goto continue_op;
 		}
 
-		blocknum = data[ssif_info->multi_len];
+		blocknum = data[0];
 
-		if (ssif_info->multi_len+len-1 > IPMI_MAX_MSG_LENGTH) {
+		if (ssif_info->multi_len + len - 1 > IPMI_MAX_MSG_LENGTH) {
 			/* Received message too big, abort the operation. */
 			result = -E2BIG;
 			if (ssif_info->ssif_debug & SSIF_DEBUG_MSG)
@@ -672,15 +673,15 @@ static void msg_done_handler(struct ssif_info *ssif_info, int result,
 		}
 
 		/* Remove the blocknum from the data. */
-		for (i = 0; i < (len-1); i++)
-			ssif_info->data[i+ssif_info->multi_len] = data[i+1];
 		len--;
+		for (i = 0; i < len; i++)
+			ssif_info->data[i + ssif_info->multi_len] = data[i + 1];
 		ssif_info->multi_len += len;
 		if (blocknum == 0xff) {
 			/* End of read */
 			len = ssif_info->multi_len;
 			data = ssif_info->data;
-		} else if ((blocknum+1) != ssif_info->multi_pos) {
+		} else if (blocknum + 1 != ssif_info->multi_pos) {
 			/*
 			 * Out of sequence block, just abort.  Block
 			 * numbers start at zero for the second block,
@@ -880,7 +881,11 @@ static void msg_written_handler(struct ssif_info *ssif_info, int result,
 	}
 
 	if (ssif_info->multi_data) {
-		/* In the middle of a multi-data write. */
+		/*
+		 * In the middle of a multi-data write.  See the comment
+		 * in the SSIF_MULTI_n_PART case in the probe function
+		 * for details on the intricacies of this.
+		 */
 		int left;
 
 		ssif_inc_stat(ssif_info, sent_messages_parts);
@@ -984,7 +989,7 @@ static int start_send(struct ssif_info *ssif_info,
 		return -E2BIG;
 
 	ssif_info->retries_left = SSIF_SEND_RETRIES;
-	memcpy(ssif_info->data+1, data, len);
+	memcpy(ssif_info->data + 1, data, len);
 	ssif_info->data_len = len;
 	return start_resend(ssif_info);
 }
@@ -1487,13 +1492,33 @@ static int ssif_probe(struct i2c_client *client, const struct i2c_device_id *id)
 			break;
 
 		case SSIF_MULTI_2_PART:
-			if (ssif_info->max_xmit_msg_size > 64)
-				ssif_info->max_xmit_msg_size = 64;
+			if (ssif_info->max_xmit_msg_size > 63)
+				ssif_info->max_xmit_msg_size = 63;
 			if (ssif_info->max_recv_msg_size > 62)
 				ssif_info->max_recv_msg_size = 62;
 			break;
 
 		case SSIF_MULTI_n_PART:
+			/*
+			 * The specification is rather confusing at
+			 * this point, but I think I understand what
+			 * is meant.  At least I have a workable
+			 * solution.  With multi-part messages, you
+			 * cannot send a message that is a multiple of
+			 * 32-bytes in length, because the start and
+			 * middle messages are 32-bytes and the end
+			 * message must be at least one byte.  You
+			 * can't fudge on an extra byte, that would
+			 * screw up things like fru data writes.  So
+			 * we limit the length to 63 bytes.  That way
+			 * a 32-byte message gets sent as a single
+			 * part.  A larger message will be a 32-byte
+			 * start and the next message is always going
+			 * to be 1-31 bytes in length.  Not ideal, but
+			 * it should work.
+			 */
+			if (ssif_info->max_xmit_msg_size > 63)
+				ssif_info->max_xmit_msg_size = 63;
 			break;
 
 		default: