Re: [PATCH v5 4/4] iio: adc: ad9467: check for backend capabilities

Nuno Sá
2026-02-02T10:41:39Z

On Fri, 2026-01-30 at 09:17 +0000, Tomas Melin wrote:
> Add capability checks for operation with backends that do not necessarily
> support full set of features, but are otherwise compatible with the device.
> This ensures a fully functional device, but with limited capabilities.
>
> Signed-off-by: Tomas Melin <tomas.melin@vaisala.com>
> ---
>  drivers/iio/adc/ad9467.c | 69 ++++++++++++++++++++++++++++++------------------
>  1 file changed, 43 insertions(+), 26 deletions(-)
>
> diff --git a/drivers/iio/adc/ad9467.c b/drivers/iio/adc/ad9467.c
> index 59c3fa3bcc9b..d768f7bf2a1c 100644
> --- a/drivers/iio/adc/ad9467.c
> +++ b/drivers/iio/adc/ad9467.c
> @@ -913,7 +913,9 @@ static int __ad9467_update_clock(struct ad9467_state *st, long r_clk)
>   return ret;
>
>   guard(mutex)(&st->lock);
> - return ad9467_calibrate(st);
> + if (iio_backend_has_caps(st->back, IIO_BACKEND_CAP_CALIBRATION))
> + return ad9467_calibrate(st);
> + return 0;
>  }
>
>  static int ad9467_write_raw(struct iio_dev *indio_dev,
> @@ -1119,12 +1121,15 @@ static ssize_t ad9467_chan_test_mode_read(struct file *file,
>   len = scnprintf(buf, sizeof(buf), "Running \"%s\" Test:\n\t",
>   ad9467_test_modes[chan->mode]);
>
> - ret = iio_backend_debugfs_print_chan_status(st->back, chan->idx,
> -     buf + len,
> -     sizeof(buf) - len);
> - if (ret < 0)
> - return ret;
> - len += ret;
> + if (iio_backend_has_caps(st->back, IIO_BACKEND_CAP_CALIBRATION)) {
> + ret = iio_backend_debugfs_print_chan_status(st->back,
> +     chan->idx,
> +     buf + len,
> +     sizeof(buf) - len);
> + if (ret < 0)
> + return ret;
> + len += ret;

Given that we can't really check the status we could maybe do this in a better way. See
below...
> + }
>   } else if (chan->mode == AN877_ADC_TESTMODE_OFF) {
>   len = scnprintf(buf, sizeof(buf), "No test Running...\n");
>   } else {
> @@ -1188,16 +1193,19 @@ static ssize_t ad9467_chan_test_mode_write(struct file *file,
>   return ret;
>
>   /*  some patterns have a backend matching monitoring block */
> - if (mode == AN877_ADC_TESTMODE_PN9_SEQ) {
> - ret = ad9467_backend_testmode_on(st, chan->idx,
> + if (iio_backend_has_caps(st->back,
> + IIO_BACKEND_CAP_CALIBRATION)) {
> + if (mode == AN877_ADC_TESTMODE_PN9_SEQ) {
> + ret = ad9467_backend_testmode_on(st, chan->idx,
>   IIO_BACKEND_ADI_PRBS_9A);
> - if (ret)
> - return ret;
> - } else if (mode == AN877_ADC_TESTMODE_PN23_SEQ) {
> - ret = ad9467_backend_testmode_on(st, chan->idx,
> + if (ret)
> + return ret;
> + } else if (mode == AN877_ADC_TESTMODE_PN23_SEQ) {
> + ret = ad9467_backend_testmode_on(st, chan->idx,
>   IIO_BACKEND_ADI_PRBS_23A);
> - if (ret)
> - return ret;
> + if (ret)
> + return ret;
> + }
>   }
>   }
>
> @@ -1263,8 +1271,10 @@ static void ad9467_debugfs_init(struct iio_dev *indio_dev)
>   if (!st->chan_test)
>   return;
>
> - debugfs_create_file("calibration_table_dump", 0400, d, st,
> -     &ad9467_calib_table_fops);
> + if (iio_backend_has_caps(st->back, IIO_BACKEND_CAP_CALIBRATION)) {
> + debugfs_create_file("calibration_table_dump", 0400, d, st,
> +     &ad9467_calib_table_fops);
> + }
>
>   for (chan = 0; chan < st->info->num_channels; chan++) {
>   snprintf(attr_name, sizeof(attr_name), "in_voltage%u_test_mode",

Change the permissions for in_voltage%u_test_mode so that is WO in case we can't
IIO_BACKEND_CAP_CALIBRATION. You can even reuse the above check to tweak the permissions
accordingly. Then no need to check for the capability in ad9467_chan_test_mode_read()

- Nuno Sá