CHROMIUM: Input: atmel_mxt_ts - refactor mxt_read/write_reg to take a length

The i2c bus requires 5 bytes to do a 1 byte read (1-byte i2c address + 2
byte offset + 1-byte i2c address + 1 byte data), or 4 bytes to do a
1-byte write (1 byte i2c address + 2 byte offset + 1 byte data).

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

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

Signed-off-by: Daniel Kurtz <djkurtz@chromium.org>
BUG=chromium-os:27713
TEST=builds clean

Change-Id: I00a08856733de3ff4d5b8bf65d53107f981674e8
Reviewed-on: https://gerrit.chromium.org/gerrit/17942
Commit-Ready: Daniel Kurtz <djkurtz@chromium.org>
Reviewed-by: Daniel Kurtz <djkurtz@chromium.org>
Tested-by: Daniel Kurtz <djkurtz@chromium.org>

diff --git a/drivers/input/touchscreen/atmel_mxt_ts.c b/drivers/input/touchscreen/atmel_mxt_ts.c
index d238d80..0c960cc 100644 (file)
--- a/drivers/input/touchscreen/atmel_mxt_ts.c
+++ b/drivers/input/touchscreen/atmel_mxt_ts.c
@@ -397,8 +397,7 @@ static int mxt_fw_write(struct i2c_client *client,
        return 0;
 }
 
-static int __mxt_read_reg(struct i2c_client *client,
-                              u16 reg, u16 len, void *val)
+static int mxt_read_reg(struct i2c_client *client, u16 reg, u16 len, void *val)
 {
        struct i2c_msg xfer[2];
        u8 buf[2];
@@ -419,28 +418,25 @@ static int __mxt_read_reg(struct i2c_client *client,
        xfer[1].buf = val;
 
        if (i2c_transfer(client->adapter, xfer, 2) != 2) {
-               dev_err(&client->dev, "%s: i2c transfer failed\n", __func__);
+               dev_err(&client->dev, "%s: i2c read failed\n", __func__);
                return -EIO;
        }
 
        return 0;
 }
 
-static int mxt_read_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)
 {
-       return __mxt_read_reg(client, reg, 1, val);
-}
-
-static int mxt_write_reg(struct i2c_client *client, u16 reg, u8 val)
-{
-       u8 buf[3];
+       size_t count = 2 + len;         /* + 2-byte offset */
+       u8 buf[count];
 
        buf[0] = reg & 0xff;
        buf[1] = (reg >> 8) & 0xff;
-       buf[2] = val;
+       memcpy(&buf[2], val, len);
 
-       if (i2c_master_send(client, buf, 3) != 3) {
-               dev_err(&client->dev, "%s: i2c send failed\n", __func__);
+       if (i2c_master_send(client, buf, count) != count) {
+               dev_err(&client->dev, "%s: i2c write failed\n", __func__);
                return -EIO;
        }
 
@@ -450,8 +446,7 @@ static int mxt_write_reg(struct i2c_client *client, u16 reg, u8 val)
 static int mxt_read_object_table(struct i2c_client *client,
                                      u16 reg, u8 *object_buf)
 {
-       return __mxt_read_reg(client, reg, MXT_OBJECT_SIZE,
-                                  object_buf);
+       return mxt_read_reg(client, reg, MXT_OBJECT_SIZE, object_buf);
 }
 
 static struct mxt_object *
@@ -481,8 +476,8 @@ static int mxt_read_message(struct mxt_data *data,
                return -EINVAL;
 
        reg = object->start_address;
-       return __mxt_read_reg(data->client, reg,
-                       sizeof(struct mxt_message), message);
+       return mxt_read_reg(data->client, reg, sizeof(struct mxt_message),
+                           message);
 }
 
 static int mxt_read_object(struct mxt_data *data,
@@ -496,7 +491,7 @@ static int mxt_read_object(struct mxt_data *data,
                return -EINVAL;
 
        reg = object->start_address;
-       return __mxt_read_reg(data->client, reg + offset, 1, val);
+       return mxt_read_reg(data->client, reg + offset, 1, val);
 }
 
 static int mxt_write_object(struct mxt_data *data,
@@ -510,7 +505,7 @@ static int mxt_write_object(struct mxt_data *data,
                return -EINVAL;
 
        reg = object->start_address;
-       return mxt_write_reg(data->client, reg + offset, val);
+       return mxt_write_reg(data->client, reg + offset, 1, &val);
 }
 
 static void mxt_input_report(struct mxt_data *data, int single_id)
@@ -757,27 +752,27 @@ static int mxt_get_info(struct mxt_data *data)
        int error;
        u8 val;
 
-       error = mxt_read_reg(client, MXT_FAMILY_ID, &val);
+       error = mxt_read_reg(client, MXT_FAMILY_ID, 1, &val);
        if (error)
                return error;
        info->family_id = val;
 
-       error = mxt_read_reg(client, MXT_VARIANT_ID, &val);
+       error = mxt_read_reg(client, MXT_VARIANT_ID, 1, &val);
        if (error)
                return error;
        info->variant_id = val;
 
-       error = mxt_read_reg(client, MXT_VERSION, &val);
+       error = mxt_read_reg(client, MXT_VERSION, 1, &val);
        if (error)
                return error;
        info->version = val;
 
-       error = mxt_read_reg(client, MXT_BUILD, &val);
+       error = mxt_read_reg(client, MXT_BUILD, 1, &val);
        if (error)
                return error;
        info->build = val;
 
-       error = mxt_read_reg(client, MXT_OBJECT_NUM, &val);
+       error = mxt_read_reg(client, MXT_OBJECT_NUM, 1, &val);
        if (error)
                return error;
        info->object_num = val;
@@ -860,12 +855,12 @@ static int mxt_initialize(struct mxt_data *data)
        msleep(MXT_RESET_TIME);
 
        /* Update matrix size at info struct */
-       error = mxt_read_reg(client, MXT_MATRIX_X_SIZE, &val);
+       error = mxt_read_reg(client, MXT_MATRIX_X_SIZE, 1, &val);
        if (error)
                return error;
        info->matrix_xsize = val;
 
-       error = mxt_read_reg(client, MXT_MATRIX_Y_SIZE, &val);
+       error = mxt_read_reg(client, MXT_MATRIX_Y_SIZE, 1, &val);
        if (error)
                return error;
        info->matrix_ysize = val;