Re: [PATCH v2] IIO ADC support for AD7923

From: Lars-Peter Clausen
Date: Tue Feb 12 2013 - 13:53:24 EST


On 02/12/2013 06:10 PM, Christophe Leroy wrote:
> This patch adds support for Analog Devices AD7923 ADC in the IIO Subsystem.
>
> Signed-off-by: Patrick Vasseur <patrick.vasseur@xxxxxx>
> Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxx>

Looks good to me except for one small, but important issue.

[...]
> diff -urN linux-next-e347c98/drivers/iio/adc/ad7923.c linux-next-e347c98.new/drivers/iio/adc/ad7923.c
> --- linux-next-e347c98/drivers/iio/adc/ad7923.c 1970-01-01 01:00:00.000000000 +0100
> +++ linux-next-e347c98.new/drivers/iio/adc/ad7923.c 2013-02-12 15:16:29.000000000 +0100
[...]
> +
> +struct ad7923_state {
> + struct spi_device *spi;
> + struct spi_transfer ring_xfer[6];

I think 5 is the max number of transfers, one for each channel and one extra to
read the last result.

> + struct spi_transfer scan_single_xfer[2];
> + struct spi_message ring_msg;
> + struct spi_message scan_single_msg;
> + /*
> + * DMA (thus cache coherency maintenance) requires the
> + * transfer buffers to live in their own cache lines.
> + */
> + __be16 rx_buf[4] ____cacheline_aligned;
> + __be16 tx_buf[2];

The tx buffer also needs to be 4 elements.

> +};
[...]
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