linux-kernel - Re: [PATCH v1 1/2] iio: adc: ti-adc128s052: Use get_unaligned

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Date:   Fri, 23 Dec 2022 15:17:50 +0000
From:   Jonathan Cameron <jic23@...nel.org>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
        Lars-Peter Clausen <lars@...afoo.de>
Subject: Re: [PATCH v1 1/2] iio: adc: ti-adc128s052: Use
 get_unaligned_beXX()

On Wed, 14 Dec 2022 14:02:01 +0200
Andy Shevchenko <andriy.shevchenko@...ux.intel.com> wrote:

> This makes the driver code slightly easier to read.
> While at it, use GENMASK() as well.
> 
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Hi Andy,

Patch looks good, but it got me thinking.  Why not just flip this driver
over to using spi_write_then_read().  Would let us drop the DMA safety
protections and simplify the code + use a __be16 as the read buffer
and this would then be the slightly nicer aligned form.

Worth doing whilst you are here?

Jonathan

> ---
>  drivers/iio/adc/ti-adc128s052.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iio/adc/ti-adc128s052.c b/drivers/iio/adc/ti-adc128s052.c
> index fc09ee6bb174..7c4e8025861c 100644
> --- a/drivers/iio/adc/ti-adc128s052.c
> +++ b/drivers/iio/adc/ti-adc128s052.c
> @@ -9,6 +9,7 @@
>   * https://www.ti.com/lit/ds/symlink/adc124s021.pdf
>   */
>  
> +#include <linux/bits.h>
>  #include <linux/err.h>
>  #include <linux/spi/spi.h>
>  #include <linux/module.h>
> @@ -17,6 +18,8 @@
>  #include <linux/property.h>
>  #include <linux/regulator/consumer.h>
>  
> +#include <asm/unaligned.h>
> +
>  struct adc128_configuration {
>  	const struct iio_chan_spec	*channels;
>  	u8				num_channels;
> @@ -33,6 +36,7 @@ struct adc128 {
>  
>  static int adc128_adc_conversion(struct adc128 *adc, u8 channel)
>  {
> +	u16 value;
>  	int ret;
>  
>  	mutex_lock(&adc->lock);
> @@ -53,7 +57,8 @@ static int adc128_adc_conversion(struct adc128 *adc, u8 channel)
>  	if (ret < 0)
>  		return ret;
>  
> -	return ((adc->buffer[0] << 8 | adc->buffer[1]) & 0xFFF);
> +	value = get_unaligned_be16(&adc->buffer);
> +	return value & GENMASK(11, 0);
>  }
>  
>  static int adc128_read_raw(struct iio_dev *indio_dev,