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

Tomas Melin
2026-02-02T11:19:24Z

Hi,

On 31/01/2026 22:40, David Lechner wrote:
> On 1/30/26 3:17 AM, 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);
>
> I saw in the changelog that leaving the guard here was intentional, but I
> don't see why.

This was discussed here:
https://marc.info/?l=linux-iio&m=176900394618857&w=4

>
>> - 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;
>> + }
>> } 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",
>
>
> Do we actually need to change these test mode/debugfs functions since
> debugfs_create_file() is only callded if IIO_BACKEND_CAP_CALIBRATION
> already?

The set of available test modes as such are part of the device, not the
backend. Based on that I have concluded that they should remain intact.

Thanks,
Tomas

>
>