Re: [PATCH 2/2] iio: proximity: add support for PulsedLight LIDAR

On 02/08/15 19:39, Lars-Peter Clausen wrote:

On 08/02/2015 08:23 PM, Jonathan Cameron wrote:

quoted

On 02/08/15 10:42, Lars-Peter Clausen wrote:

quoted

On 08/01/2015 05:58 AM, Matt Ranostay wrote:
[...]

quoted

+
+struct lidar_data {
+	struct mutex lock;
+	struct iio_dev *indio_dev;
+	struct i2c_client *client;
+
+	/* config */
+	int calib_bias;
+
+	u16 buffer[5]; /* 2 byte distance + 8 byte timestamp */

Needs to be in its own cacheline to avoid issues if the I2C controller is
using DMA.

Would do if spi, but in the case of i2c I thought all bus drivers were
obliged to deal with this rather than leaving it to the client drivers?

Where did you find this? There definitely seem to be I2C drivers which
directly map the i2c_msg buffers.

Right now I can't track down an explicit reference.  However, all sorts
of nastiness occurs if we end up using the i2c_smbus_xfer_emulated as
that uses local buffers on the stack.

Hmm. Will look into this more when I get a chance.  We have a lot of
i2c drivers that don't have aligned buffers...

But I just realized that in this case the buffer is not passed to the i2c
driver anyway so we should be fine.

- Lars

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