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mfd: Avoid copying data in WM8994 I2C write

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As well as providing a trivial performance optimisation this also avoids
allocating a copy of the message on the stack which is beneficial when
doing large transfers.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
This commit is contained in:
Mark Brown 2011-03-17 21:42:28 +00:00 committed by Samuel Ortiz
parent 4c4d887822
commit 334e9ab8f9
1 changed files with 13 additions and 9 deletions
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22
drivers/mfd/wm8994-core.c
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@ -580,25 +580,29 @@ static int wm8994_i2c_read_device(struct wm8994 *wm8994, unsigned short reg,
return 0;
}
/* Currently we allocate the write buffer on the stack; this is OK for
* small writes - if we need to do large writes this will need to be
* revised.
*/
static int wm8994_i2c_write_device(struct wm8994 *wm8994, unsigned short reg,
int bytes, void *src)
{
struct i2c_client *i2c = wm8994->control_data;
unsigned char msg[bytes + 2];
struct i2c_msg xfer[2];
int ret;
reg = cpu_to_be16(reg);
memcpy(&msg[0], &reg, 2);
memcpy(&msg[2], src, bytes);
ret = i2c_master_send(i2c, msg, bytes + 2);
xfer[0].addr = i2c->addr;
xfer[0].flags = 0;
xfer[0].len = 2;
xfer[0].buf = (char *)&reg;
xfer[1].addr = i2c->addr;
xfer[1].flags = I2C_M_NOSTART;
xfer[1].len = bytes;
xfer[1].buf = (char *)src;
ret = i2c_transfer(i2c->adapter, xfer, 2);
if (ret < 0)
return ret;
if (ret < bytes + 2)
if (ret != 2)
return -EIO;
return 0;