[RFC PATCH 8/9] hwmon: lis3: use block read to access data registers

[Samu Onkalo <samu.p.onkalo-xNZwKgViW5gAvxtiuMwx3w@public.gmane.org>]

Add optional blockread function to interface driver. If available
the chip driver uses it for data register access. For 12 bit device
it reads 6 bytes to get 3*16bit data. For 8 bit device it reads out
5 bytes since every second byte is dummy.
This optimizes bus usage and reduces number of operations and
interrupts needed for one data update.

Signed-off-by: Samu Onkalo <samu.p.onkalo-xNZwKgViW5gAvxtiuMwx3w@public.gmane.org>
---
 drivers/hwmon/lis3lv02d.c     |   21 ++++++++++++++++++---
 drivers/hwmon/lis3lv02d.h     |    1 +
 drivers/hwmon/lis3lv02d_i2c.c |    9 +++++++++
 3 files changed, 28 insertions(+), 3 deletions(-)

diff --git a/drivers/hwmon/lis3lv02d.c b/drivers/hwmon/lis3lv02d.c
index b740024..469f251 100644
--- a/drivers/hwmon/lis3lv02d.c
+++ b/drivers/hwmon/lis3lv02d.c
@@ -129,9 +129,24 @@ static void lis3lv02d_get_xyz(struct lis3lv02d *lis3, int *x, int *y, int *z)
 	int position[3];
 	int i;
 
-	position[0] = lis3->read_data(lis3, OUTX);
-	position[1] = lis3->read_data(lis3, OUTY);
-	position[2] = lis3->read_data(lis3, OUTZ);
+	if (lis3->blkread) {
+		if (lis3_dev.whoami == WAI_12B) {
+			u16 data[3];
+			lis3->blkread(lis3, OUTX_L, 6, (u8 *)data);
+			for (i = 0; i < 3; i++)
+				position[i] = (s16)le16_to_cpu(data[i]);
+		} else {
+			u8 data[5];
+			/* Data: x, dummy, y, dummy, z */
+			lis3->blkread(lis3, OUTX, 5, data);
+			for (i = 0; i < 3; i++)
+				position[i] = (s8)data[i * 2];
+		}
+	} else {
+		position[0] = lis3->read_data(lis3, OUTX);
+		position[1] = lis3->read_data(lis3, OUTY);
+		position[2] = lis3->read_data(lis3, OUTZ);
+	}
 
 	for (i = 0; i < 3; i++)
 		position[i] = (position[i] * lis3->scale) / LIS3_ACCURACY;
diff --git a/drivers/hwmon/lis3lv02d.h b/drivers/hwmon/lis3lv02d.h
index 1522855..cfff63c 100644
--- a/drivers/hwmon/lis3lv02d.h
+++ b/drivers/hwmon/lis3lv02d.h
@@ -232,6 +232,7 @@ struct lis3lv02d {
 	int (*init) (struct lis3lv02d *lis3);
 	int (*write) (struct lis3lv02d *lis3, int reg, u8 val);
 	int (*read) (struct lis3lv02d *lis3, int reg, u8 *ret);
+	int (*blkread) (struct lis3lv02d *lis3, int reg, int len, u8 *ret);
 	int (*reg_ctrl) (struct lis3lv02d *lis3, bool state);
 
 	int                     *odrs;     /* Supported output data rates */
diff --git a/drivers/hwmon/lis3lv02d_i2c.c b/drivers/hwmon/lis3lv02d_i2c.c
index c5a60e4..1e0673b 100644
--- a/drivers/hwmon/lis3lv02d_i2c.c
+++ b/drivers/hwmon/lis3lv02d_i2c.c
@@ -66,6 +66,14 @@ static inline s32 lis3_i2c_read(struct lis3lv02d *lis3, int reg, u8 *v)
 	return 0;
 }
 
+static inline s32 lis3_i2c_blockread(struct lis3lv02d *lis3, int reg, int len,
+				u8 *v)
+{
+	struct i2c_client *c = lis3->bus_priv;
+	reg |= (1 << 7); /* 7th bit enables address auto incrementation */
+	return i2c_smbus_read_i2c_block_data(c, reg, len, v);
+}
+
 static int lis3_i2c_init(struct lis3lv02d *lis3)
 {
 	u8 reg;
@@ -125,6 +133,7 @@ static int __devinit lis3lv02d_i2c_probe(struct i2c_client *client,
 	lis3_dev.bus_priv = client;
 	lis3_dev.init	  = lis3_i2c_init;
 	lis3_dev.read	  = lis3_i2c_read;
+	lis3_dev.blkread  = lis3_i2c_blockread;
 	lis3_dev.write	  = lis3_i2c_write;
 	lis3_dev.reg_ctrl = lis3_reg_ctrl;
 	lis3_dev.irq	  = client->irq;
-- 
1.6.0.4