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Commit 334e9ab8 authored by Mark Brown's avatar Mark Brown Committed by Samuel Ortiz
Browse files

mfd: Avoid copying data in WM8994 I2C write 



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: default avatarMark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: default avatarSamuel Ortiz <sameo@linux.intel.com>
parent 4c4d8878

drivers/mfd/wm8994-core.c

+13 −9
Original line number Diff line number Diff line
@@ -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;