1 files changed, 75 insertions, 12 deletions

diff --git a/drivers/iio/adc/ad7173.c b/drivers/iio/adc/ad7173.c
index 4413207be28f..683146e83ab2 100644
--- a/drivers/iio/adc/ad7173.c
+++ b/drivers/iio/adc/ad7173.c
@@ -200,7 +200,7 @@ struct ad7173_channel_config {
 	/*
 	 * Following fields are used to compare equality. If you
 	 * make adaptations in it, you most likely also have to adapt
-	 * ad7173_find_live_config(), too.
+	 * ad7173_is_setup_equal(), too.
 	 */
 	struct_group(config_props,
 		bool bipolar;
@@ -561,12 +561,19 @@ static void ad7173_reset_usage_cnts(struct ad7173_state *st)
 	st->config_usage_counter = 0;
 }
 
-static struct ad7173_channel_config *
-ad7173_find_live_config(struct ad7173_state *st, struct ad7173_channel_config *cfg)
+/**
+ * ad7173_is_setup_equal - Compare two channel setups
+ * @cfg1: First channel configuration
+ * @cfg2: Second channel configuration
+ *
+ * Compares all configuration options that affect the registers connected to
+ * SETUP_SEL, namely CONFIGx, FILTERx, GAINx and OFFSETx.
+ *
+ * Returns: true if the setups are identical, false otherwise
+ */
+static bool ad7173_is_setup_equal(const struct ad7173_channel_config *cfg1,
+				  const struct ad7173_channel_config *cfg2)
 {
-	struct ad7173_channel_config *cfg_aux;
-	int i;
-
 	/*
 	 * This is just to make sure that the comparison is adapted after
 	 * struct ad7173_channel_config was changed.
@@ -579,14 +586,22 @@ ad7173_find_live_config(struct ad7173_state *st, struct ad7173_channel_config *c
 				     u8 ref_sel;
 			     }));
 
+	return cfg1->bipolar == cfg2->bipolar &&
+	       cfg1->input_buf == cfg2->input_buf &&
+	       cfg1->odr == cfg2->odr &&
+	       cfg1->ref_sel == cfg2->ref_sel;
+}
+
+static struct ad7173_channel_config *
+ad7173_find_live_config(struct ad7173_state *st, struct ad7173_channel_config *cfg)
+{
+	struct ad7173_channel_config *cfg_aux;
+	int i;
+
 	for (i = 0; i < st->num_channels; i++) {
 		cfg_aux = &st->channels[i].cfg;
 
-		if (cfg_aux->live &&
-		    cfg->bipolar == cfg_aux->bipolar &&
-		    cfg->input_buf == cfg_aux->input_buf &&
-		    cfg->odr == cfg_aux->odr &&
-		    cfg->ref_sel == cfg_aux->ref_sel)
+		if (cfg_aux->live && ad7173_is_setup_equal(cfg, cfg_aux))
 			return cfg_aux;
 	}
 	return NULL;
@@ -1228,7 +1243,7 @@ static int ad7173_update_scan_mode(struct iio_dev *indio_dev,
 				   const unsigned long *scan_mask)
 {
 	struct ad7173_state *st = iio_priv(indio_dev);
-	int i, ret;
+	int i, j, k, ret;
 
 	for (i = 0; i < indio_dev->num_channels; i++) {
 		if (test_bit(i, scan_mask))
@@ -1239,6 +1254,54 @@ static int ad7173_update_scan_mode(struct iio_dev *indio_dev,
 			return ret;
 	}
 
+	/*
+	 * On some chips, there are more channels that setups, so if there were
+	 * more unique setups requested than the number of available slots,
+	 * ad7173_set_channel() will have written over some of the slots. We
+	 * can detect this by making sure each assigned cfg_slot matches the
+	 * requested configuration. If it doesn't, we know that the slot was
+	 * overwritten by a different channel.
+	 */
+	for_each_set_bit(i, scan_mask, indio_dev->num_channels) {
+		const struct ad7173_channel_config *cfg1, *cfg2;
+
+		cfg1 = &st->channels[i].cfg;
+
+		for_each_set_bit(j, scan_mask, indio_dev->num_channels) {
+			cfg2 = &st->channels[j].cfg;
+
+			/*
+			 * Only compare configs that are assigned to the same
+			 * SETUP_SEL slot and don't compare channel to itself.
+			 */
+			if (i == j || cfg1->cfg_slot != cfg2->cfg_slot)
+				continue;
+
+			/*
+			 * If we find two different configs trying to use the
+			 * same SETUP_SEL slot, then we know that the that we
+			 * have too many unique configurations requested for
+			 * the available slots and at least one was overwritten.
+			 */
+			if (!ad7173_is_setup_equal(cfg1, cfg2)) {
+				/*
+				 * At this point, there isn't a way to tell
+				 * which setups are actually programmed in the
+				 * ADC anymore, so we could read them back to
+				 * see, but it is simpler to just turn off all
+				 * of the live flags so that everything gets
+				 * reprogramed on the next attempt read a sample.
+				 */
+				for (k = 0; k < st->num_channels; k++)
+					st->channels[k].cfg.live = false;
+
+				dev_err(&st->sd.spi->dev,
+					"Too many unique channel configurations requested for scan\n");
+				return -EINVAL;
+			}
+		}
+	}
+
 	return 0;
 }