iio: jesd204: axi_adxcvr: Add access checks for eye_data and PRBS attributes

Add validation to prevent reading uninitialized eye_data and PRBS
attributes:

- eye_data binary attribute: Check if enable is written and lane != -1
- eyescan_info: Check if enable is written and lane != -1
- prbs_error_counters: Check if prbs_select was written with non-zero value
- prbs_status: Check if prbs_select was written with non-zero value

Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
Signed-off-by: Nuno Sá <nuno.sa@analog.com>

Author: Michael Hennerich

drivers/iio/jesd204/axi_adxcvr.c

@@ -310,11 +310,16 @@ static ssize_t adxcvr_prbs_error_counter_show(struct device *dev,
 				     char *buf)
 {
 	struct adxcvr_state *st = dev_get_drvdata(dev);
-	unsigned int count;
+	unsigned int count, val;
 	ssize_t len = 0;
 	int i, ret;
 
 	guard(mutex)(&st->mutex);
+
+	/* Check if prbs_select was written with non-zero value */
+	val = adxcvr_read(st, ADXCVR_REG_REG_PRBS_CNTRL);
+	if ((val & 0xF) == 0)
+		return -ENODATA;
 	for (i = 0; i < st->num_lanes; i++) {
 		ret = xilinx_xcvr_prbs_err_cnt_get(&st->xcvr,
 			ADXCVR_DRP_PORT_CHANNEL(i), &count);
@@ -364,6 +369,12 @@ static ssize_t adxcvr_prbs_status_show(struct device *dev,
 	const char *status;
 
 	guard(mutex)(&st->mutex);
+
+	/* Check if prbs_select was written with non-zero value */
+	val = adxcvr_read(st, ADXCVR_REG_REG_PRBS_CNTRL);
+	if ((val & 0xF) == 0)
+		return -ENODATA;
+
 	val = adxcvr_read(st, ADXCVR_REG_REG_PRBS_STATUS);
 
 	if (ADXCVR_PRBS_LOCKED(val))

drivers/iio/jesd204/axi_adxcvr_eyescan.c

@@ -187,6 +187,10 @@ adxcvr_eyescan_bin_read(struct file *filp, struct kobject *kobj,
 	dev = container_of(kobj, struct device, kobj);
 	st = dev_get_drvdata(dev);
 
+	/* Check if eye scan is enabled and lane is set */
+	if (st->eye->lane == -1)
+		return -ENODATA;
+
 	if (unlikely(off >= st->eye->bin.size))
 		return 0;
 	if ((off + count) > st->eye->bin.size)
@@ -334,6 +338,10 @@ static ssize_t adxcvr_eyescan_info_read(struct device *dev,
 	u32 hsize;
 	int ret;
 
+	/* Check if eye scan is enabled and lane is set */
+	if (st->eye->lane == -1)
+		return -ENODATA;
+
 	ret = adxcvr_get_eyescan_es_hsize(st, &hsize);
 	if (ret < 0)
 		return ret;