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>
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@ -580,25 +580,29 @@ static int wm8994_i2c_read_device(struct wm8994 *wm8994, unsigned short reg,
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return 0;
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}
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/* Currently we allocate the write buffer on the stack; this is OK for
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* small writes - if we need to do large writes this will need to be
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* revised.
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*/
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static int wm8994_i2c_write_device(struct wm8994 *wm8994, unsigned short reg,
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int bytes, void *src)
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{
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struct i2c_client *i2c = wm8994->control_data;
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unsigned char msg[bytes + 2];
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struct i2c_msg xfer[2];
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int ret;
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reg = cpu_to_be16(reg);
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memcpy(&msg[0], ®, 2);
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memcpy(&msg[2], src, bytes);
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ret = i2c_master_send(i2c, msg, bytes + 2);
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xfer[0].addr = i2c->addr;
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xfer[0].flags = 0;
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xfer[0].len = 2;
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xfer[0].buf = (char *)®
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xfer[1].addr = i2c->addr;
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xfer[1].flags = I2C_M_NOSTART;
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xfer[1].len = bytes;
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xfer[1].buf = (char *)src;
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ret = i2c_transfer(i2c->adapter, xfer, 2);
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if (ret < 0)
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return ret;
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if (ret < bytes + 2)
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if (ret != 2)
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return -EIO;
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return 0;
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