Re: [PATCH 07/15] iio:ad5791: Do not store transfer buffers on the stack

[Jonathan Cameron <jic23@kernel.org>]

On 11/25/13 12:41, Lars-Peter Clausen wrote:
> Some SPI controllers may not be able to handle transfer buffers that are placed
> on the stack.
> 
> Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Applied to the togreg branch of iio.git

Thanks
> ---
>  drivers/iio/dac/ad5791.c | 46 +++++++++++++++++++++-------------------------
>  1 file changed, 21 insertions(+), 25 deletions(-)
> 
> diff --git a/drivers/iio/dac/ad5791.c b/drivers/iio/dac/ad5791.c
> index 1e7f4cd..79bf199 100644
> --- a/drivers/iio/dac/ad5791.c
> +++ b/drivers/iio/dac/ad5791.c
> @@ -91,6 +91,11 @@ struct ad5791_state {
>  	unsigned			ctrl;
>  	unsigned			pwr_down_mode;
>  	bool				pwr_down;
> +
> +	union {
> +		__be32 d32;
> +		u8 d8[4];
> +	} data[3] ____cacheline_aligned;
>  };
>  
>  /**
> @@ -104,48 +109,39 @@ enum ad5791_supported_device_ids {
>  	ID_AD5791,
>  };
>  
> -static int ad5791_spi_write(struct spi_device *spi, u8 addr, u32 val)
> +static int ad5791_spi_write(struct ad5791_state *st, u8 addr, u32 val)
>  {
> -	union {
> -		__be32 d32;
> -		u8 d8[4];
> -	} data;
> -
> -	data.d32 = cpu_to_be32(AD5791_CMD_WRITE |
> +	st->data[0].d32 = cpu_to_be32(AD5791_CMD_WRITE |
>  			      AD5791_ADDR(addr) |
>  			      (val & AD5791_DAC_MASK));
>  
> -	return spi_write(spi, &data.d8[1], 3);
> +	return spi_write(st->spi, &st->data[0].d8[1], 3);
>  }
>  
> -static int ad5791_spi_read(struct spi_device *spi, u8 addr, u32 *val)
> +static int ad5791_spi_read(struct ad5791_state *st, u8 addr, u32 *val)
>  {
> -	union {
> -		__be32 d32;
> -		u8 d8[4];
> -	} data[3];
>  	int ret;
>  	struct spi_transfer xfers[] = {
>  		{
> -			.tx_buf = &data[0].d8[1],
> +			.tx_buf = &st->data[0].d8[1],
>  			.bits_per_word = 8,
>  			.len = 3,
>  			.cs_change = 1,
>  		}, {
> -			.tx_buf = &data[1].d8[1],
> -			.rx_buf = &data[2].d8[1],
> +			.tx_buf = &st->data[1].d8[1],
> +			.rx_buf = &st->data[2].d8[1],
>  			.bits_per_word = 8,
>  			.len = 3,
>  		},
>  	};
>  
> -	data[0].d32 = cpu_to_be32(AD5791_CMD_READ |
> +	st->data[0].d32 = cpu_to_be32(AD5791_CMD_READ |
>  			      AD5791_ADDR(addr));
> -	data[1].d32 = cpu_to_be32(AD5791_ADDR(AD5791_ADDR_NOOP));
> +	st->data[1].d32 = cpu_to_be32(AD5791_ADDR(AD5791_ADDR_NOOP));
>  
> -	ret = spi_sync_transfer(spi, xfers, ARRAY_SIZE(xfers));
> +	ret = spi_sync_transfer(st->spi, xfers, ARRAY_SIZE(xfers));
>  
> -	*val = be32_to_cpu(data[2].d32);
> +	*val = be32_to_cpu(st->data[2].d32);
>  
>  	return ret;
>  }
> @@ -210,7 +206,7 @@ static ssize_t ad5791_write_dac_powerdown(struct iio_dev *indio_dev,
>  	}
>  	st->pwr_down = pwr_down;
>  
> -	ret = ad5791_spi_write(st->spi, AD5791_ADDR_CTRL, st->ctrl);
> +	ret = ad5791_spi_write(st, AD5791_ADDR_CTRL, st->ctrl);
>  
>  	return ret ? ret : len;
>  }
> @@ -263,7 +259,7 @@ static int ad5791_read_raw(struct iio_dev *indio_dev,
>  
>  	switch (m) {
>  	case IIO_CHAN_INFO_RAW:
> -		ret = ad5791_spi_read(st->spi, chan->address, val);
> +		ret = ad5791_spi_read(st, chan->address, val);
>  		if (ret)
>  			return ret;
>  		*val &= AD5791_DAC_MASK;
> @@ -330,7 +326,7 @@ static int ad5791_write_raw(struct iio_dev *indio_dev,
>  		val &= AD5791_RES_MASK(chan->scan_type.realbits);
>  		val <<= chan->scan_type.shift;
>  
> -		return ad5791_spi_write(st->spi, chan->address, val);
> +		return ad5791_spi_write(st, chan->address, val);
>  
>  	default:
>  		return -EINVAL;
> @@ -393,7 +389,7 @@ static int ad5791_probe(struct spi_device *spi)
>  		dev_warn(&spi->dev, "reference voltage unspecified\n");
>  	}
>  
> -	ret = ad5791_spi_write(spi, AD5791_ADDR_SW_CTRL, AD5791_SWCTRL_RESET);
> +	ret = ad5791_spi_write(st, AD5791_ADDR_SW_CTRL, AD5791_SWCTRL_RESET);
>  	if (ret)
>  		goto error_disable_reg_neg;
>  
> @@ -405,7 +401,7 @@ static int ad5791_probe(struct spi_device *spi)
>  		  | ((pdata && pdata->use_rbuf_gain2) ? 0 : AD5791_CTRL_RBUF) |
>  		  AD5791_CTRL_BIN2SC;
>  
> -	ret = ad5791_spi_write(spi, AD5791_ADDR_CTRL, st->ctrl |
> +	ret = ad5791_spi_write(st, AD5791_ADDR_CTRL, st->ctrl |
>  		AD5791_CTRL_OPGND | AD5791_CTRL_DACTRI);
>  	if (ret)
>  		goto error_disable_reg_neg;
>