Re: [PATCH v5 3/6] iio: imu: adis: Add DIAG_STAT register size

[Jonathan Cameron <jic23@kernel.org>]

On Wed, 29 Jan 2025 10:20:43 +0200
Robert Budai <robert.budai@analog.com> wrote:

> Some devices may have more than 16 bits of status. This patch allows the
> user to specify the size of the DIAG_STAT register. It defaults to 2 if
> not specified. This is mainly for backward compatibility.
> 
> Co-developed-by: Ramona Gradinariu <ramona.gradinariu@analog.com>
> Signed-off-by: Ramona Gradinariu <ramona.gradinariu@analog.com>
> Co-developed-by: Antoniu Miclaus <antoniu.miclaus@analog.com>
> Signed-off-by: Antoniu Miclaus <antoniu.miclaus@analog.com>
> Signed-off-by: Nuno Sá <nuno.sa@analog.com>
> Signed-off-by: Robert Budai <robert.budai@analog.com>
> ---
> 
> v5:
> - added local variable
> - mentioned default handling of diag_stat_size in comments 
> 
>  drivers/iio/imu/adis.c       | 14 +++++++++++---
>  include/linux/iio/imu/adis.h |  3 +++
>  2 files changed, 14 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/iio/imu/adis.c b/drivers/iio/imu/adis.c
> index 84344f052fb7..57e724412f52 100644
> --- a/drivers/iio/imu/adis.c
> +++ b/drivers/iio/imu/adis.c
> @@ -304,11 +304,16 @@ EXPORT_SYMBOL_NS(__adis_enable_irq, "IIO_ADISLIB");
>   */
>  int __adis_check_status(struct adis *adis)
>  {
> -	u16 status;
> +	unsigned int status;
> +	int diag_stat_bits;
>  	int ret;
>  	int i;
>  
> -	ret = __adis_read_reg_16(adis, adis->data->diag_stat_reg, &status);
> +	if (adis->data->diag_stat_size)
> +		ret = adis->ops->read(adis, adis->data->diag_stat_reg, &status,
> +				      adis->data->diag_stat_size);
> +	else
> +		ret = __adis_read_reg_16(adis, adis->data->diag_stat_reg, (u16 *)&status);

You can't just cast a pointer like this.  What happens will depend on endianness
of the host CPU.  Use a local variable for the u16 then set status = status16
or something like that.


>  	if (ret)
>  		return ret;
>  
> @@ -317,7 +322,10 @@ int __adis_check_status(struct adis *adis)
>  	if (status == 0)
>  		return 0;
>  
> -	for (i = 0; i < 16; ++i) {
> +	diag_stat_bits = BITS_PER_BYTE * (adis->data->diag_stat_size ?
> +					  adis->data->diag_stat_size : 2);
> +
> +	for (i = 0; i < diag_stat_bits; ++i) {
>  		if (status & BIT(i)) {
>  			dev_err(&adis->spi->dev, "%s.\n",
>  				adis->data->status_error_msgs[i]);
> diff --git a/include/linux/iio/imu/adis.h b/include/linux/iio/imu/adis.h
> index 13beb6a7317b..ad40fb95fcdc 100644
> --- a/include/linux/iio/imu/adis.h
> +++ b/include/linux/iio/imu/adis.h
> @@ -44,6 +44,8 @@ struct adis_timeout {
>   * @glob_cmd_reg: Register address of the GLOB_CMD register
>   * @msc_ctrl_reg: Register address of the MSC_CTRL register
>   * @diag_stat_reg: Register address of the DIAG_STAT register
> + * @diag_stat_size: Length (in bytes) of the DIAG_STAT register. If not
> + *					defined, default value is 2 bytes long.

If 0, rather than not defined (it's defined whatever, just a question of what
value it has!)

>   * @prod_id_reg: Register address of the PROD_ID register
>   * @prod_id: Product ID code that should be expected when reading @prod_id_reg
>   * @self_test_mask: Bitmask of supported self-test operations
> @@ -70,6 +72,7 @@ struct adis_data {
>  	unsigned int glob_cmd_reg;
>  	unsigned int msc_ctrl_reg;
>  	unsigned int diag_stat_reg;
> +	unsigned int diag_stat_size;
>  	unsigned int prod_id_reg;
>  
>  	unsigned int prod_id;