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authorMark Brown <broonie@opensource.wolfsonmicro.com>2011-03-17 17:42:28 -0400
committerSamuel Ortiz <sameo@linux.intel.com>2011-03-23 05:42:10 -0400
commit334e9ab8f9bb90ddf1eff0b07609961a628064b6 (patch)
tree662945d7aed6adb546ed3915186e86b2f56b3cad /drivers/mfd
parent4c4d887822070410e3be519e1a4ff933fb899ba8 (diff)
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: Mark Brown <broonie@opensource.wolfsonmicro.com> Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
Diffstat (limited to 'drivers/mfd')
-rw-r--r--drivers/mfd/wm8994-core.c22
1 files changed, 13 insertions, 9 deletions
diff --git a/drivers/mfd/wm8994-core.c b/drivers/mfd/wm8994-core.c
index 749c31d29b09..ce93796e7f57 100644
--- a/drivers/mfd/wm8994-core.c
+++ b/drivers/mfd/wm8994-core.c
@@ -580,25 +580,29 @@ static int wm8994_i2c_read_device(struct wm8994 *wm8994, unsigned short reg,
580 return 0; 580 return 0;
581} 581}
582 582
583/* Currently we allocate the write buffer on the stack; this is OK for
584 * small writes - if we need to do large writes this will need to be
585 * revised.
586 */
587static int wm8994_i2c_write_device(struct wm8994 *wm8994, unsigned short reg, 583static int wm8994_i2c_write_device(struct wm8994 *wm8994, unsigned short reg,
588 int bytes, void *src) 584 int bytes, void *src)
589{ 585{
590 struct i2c_client *i2c = wm8994->control_data; 586 struct i2c_client *i2c = wm8994->control_data;
591 unsigned char msg[bytes + 2]; 587 struct i2c_msg xfer[2];
592 int ret; 588 int ret;
593 589
594 reg = cpu_to_be16(reg); 590 reg = cpu_to_be16(reg);
595 memcpy(&msg[0], &reg, 2);
596 memcpy(&msg[2], src, bytes);
597 591
598 ret = i2c_master_send(i2c, msg, bytes + 2); 592 xfer[0].addr = i2c->addr;
593 xfer[0].flags = 0;
594 xfer[0].len = 2;
595 xfer[0].buf = (char *)&reg;
596
597 xfer[1].addr = i2c->addr;
598 xfer[1].flags = I2C_M_NOSTART;
599 xfer[1].len = bytes;
600 xfer[1].buf = (char *)src;
601
602 ret = i2c_transfer(i2c->adapter, xfer, 2);
599 if (ret < 0) 603 if (ret < 0)
600 return ret; 604 return ret;
601 if (ret < bytes + 2) 605 if (ret != 2)
602 return -EIO; 606 return -EIO;
603 607
604 return 0; 608 return 0;