linux-kernel - [PATCH v4 4/4] iio: adc: ad9467: check for backend capabilities

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Message-Id: <20260121-b4-ad9467-optional-backend-v4-4-18d2c0d450cc@vaisala.com>
Date: Wed, 21 Jan 2026 12:08:33 +0000
From: Tomas Melin <tomas.melin@...sala.com>
To: Michael Hennerich <Michael.Hennerich@...log.com>, 
 Nuno Sa <nuno.sa@...log.com>, Lars-Peter Clausen <lars@...afoo.de>, 
 Jonathan Cameron <jic23@...nel.org>, David Lechner <dlechner@...libre.com>, 
 Andy Shevchenko <andy@...nel.org>, 
 Olivier Moysan <olivier.moysan@...s.st.com>
Cc: linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Tomas Melin <tomas.melin@...sala.com>
Subject: [PATCH v4 4/4] iio: adc: ad9467: check for backend capabilities

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@...sala.com>
---
 drivers/iio/adc/ad9467.c | 72 ++++++++++++++++++++++++++++++------------------
 1 file changed, 45 insertions(+), 27 deletions(-)

diff --git a/drivers/iio/adc/ad9467.c b/drivers/iio/adc/ad9467.c
index 59c3fa3bcc9b0b8b36b78c3b54fd7977cae23496..eb57f72211430fc2c41baa9ed1a1e0ecf798ad57 100644
--- a/drivers/iio/adc/ad9467.c
+++ b/drivers/iio/adc/ad9467.c
@@ -912,8 +912,11 @@ static int __ad9467_update_clock(struct ad9467_state *st, long r_clk)
 	if (ret)
 		return ret;
 
-	guard(mutex)(&st->lock);
-	return ad9467_calibrate(st);
+	if (iio_backend_has_caps(st->back, IIO_BACKEND_CAP_CALIBRATION)) {
+		guard(mutex)(&st->lock);
+		return ad9467_calibrate(st);
+	}
+	return 0;
 }
 
 static int ad9467_write_raw(struct iio_dev *indio_dev,
@@ -1119,12 +1122,15 @@ 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 +1194,19 @@ 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 +1272,10 @@ 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",
@@ -1339,17 +1350,24 @@ static int ad9467_probe(struct spi_device *spi)
 	if (ret)
 		return ret;
 
-	ret = devm_iio_backend_request_buffer(&spi->dev, st->back, indio_dev);
-	if (ret)
-		return ret;
+	if (iio_backend_has_caps(st->back, IIO_BACKEND_CAP_BUFFERING)) {
+		ret = devm_iio_backend_request_buffer(&spi->dev, st->back,
+						      indio_dev);
+		if (ret)
+			return ret;
+	}
 
-	ret = devm_iio_backend_enable(&spi->dev, st->back);
-	if (ret)
-		return ret;
+	if (!iio_backend_has_caps(st->back, IIO_BACKEND_CAP_ALWAYS_ON)) {
+		ret = devm_iio_backend_enable(&spi->dev, st->back);
+		if (ret)
+			return ret;
+	}
 
-	ret = ad9467_calibrate(st);
-	if (ret)
-		return ret;
+	if (iio_backend_has_caps(st->back, IIO_BACKEND_CAP_CALIBRATION)) {
+		ret = ad9467_calibrate(st);
+		if (ret)
+			return ret;
+	}
 
 	ret = devm_iio_device_register(&spi->dev, indio_dev);
 	if (ret)

-- 
2.47.3