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

[Tomas Melin]

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@xxxxxxxxxxx>
>> ---
>>  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


> 
>