From 9638ab7c9c3b352d54f4f7e80027bd6e1c0584e8 Mon Sep 17 00:00:00 2001
From: Daniel Kurtz <djkurtz@chromium.org>
Date: Thu, 28 Jun 2012 21:08:12 +0800
Subject: Input: atmel_mxt_ts - add variable length __mxt_write_reg

The i2c bus requires 4 bytes to do a 1-byte write
(1 byte i2c address + 2 byte offset + 1 byte data).

By taking a length with writes, the driver can amortize transaction
overhead by performing larger transactions where appropriate.

This patch just sets up the new API.  Later patches refactor writes
to take advantage of the larger transactions.

Signed-off-by: Daniel Kurtz <djkurtz@chromium.org>
Signed-off-by: Henrik Rydberg <rydberg@euromail.se>

diff --git a/drivers/input/touchscreen/atmel_mxt_ts.c b/drivers/input/touchscreen/atmel_mxt_ts.c
index a68b227..dd2577b 100644
--- a/drivers/input/touchscreen/atmel_mxt_ts.c
+++ b/drivers/input/touchscreen/atmel_mxt_ts.c
@@ -431,17 +431,24 @@ static int mxt_read_reg(struct i2c_client *client, u16 reg, u8 *val)
 	return __mxt_read_reg(client, reg, 1, val);
 }
 
-static int mxt_write_reg(struct i2c_client *client, u16 reg, u8 val)
+static int __mxt_write_reg(struct i2c_client *client, u16 reg, u16 len,
+			   const void *val)
 {
-	u8 buf[3];
+	u8 *buf;
+	size_t count;
 	int ret;
 
+	count = len + 2;
+	buf = kmalloc(count, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
 	buf[0] = reg & 0xff;
 	buf[1] = (reg >> 8) & 0xff;
-	buf[2] = val;
+	memcpy(&buf[2], val, len);
 
-	ret = i2c_master_send(client, buf, 3);
-	if (ret == 3) {
+	ret = i2c_master_send(client, buf, count);
+	if (ret == count) {
 		ret = 0;
 	} else {
 		if (ret >= 0)
@@ -450,9 +457,15 @@ static int mxt_write_reg(struct i2c_client *client, u16 reg, u8 val)
 			__func__, ret);
 	}
 
+	kfree(buf);
 	return ret;
 }
 
+static int mxt_write_reg(struct i2c_client *client, u16 reg, u8 val)
+{
+	return __mxt_write_reg(client, reg, 1, &val);
+}
+
 static int mxt_read_object_table(struct i2c_client *client,
 				      u16 reg, u8 *object_buf)
 {
-- 
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