ols: Communicate internally that the number of samples is a multiple of 4

The exact number must be known when reading data so that we can read the
right number of samples without incuring a timeout penalty.

Author: v1ne

src/hardware/openbench-logic-sniffer/protocol.c

@@ -628,6 +628,7 @@ ols_set_basic_trigger_stage(const struct ols_basic_trigger_desc *trigger_desc,
 SR_PRIV int ols_prepare_acquisition(const struct sr_dev_inst *sdi)
 {
 	int ret;
+	uint32_t readcount, delaycount;
 
 	struct dev_context *devc = sdi->priv;
 	struct sr_serial_dev_inst *serial = sdi->conn;
@@ -643,13 +644,13 @@ SR_PRIV int ols_prepare_acquisition(const struct sr_dev_inst *sdi)
 	}
 
 	/*
-	 * Limit readcount to prevent reading past the end of the hardware
-	 * buffer. Rather read too many samples than too few.
+	 * Limit the number of samples to what the hardware can do.
+	 * The sample count is always a multiple of four.
 	 */
-	uint32_t samplecount =
-		MIN(devc->max_samples / num_changroups, devc->limit_samples);
-	uint32_t readcount = (samplecount + 3) / 4;
-	uint32_t delaycount;
+	devc->limit_samples =
+		(MIN(devc->max_samples / num_changroups, devc->limit_samples) + 3)
+		/ 4 * 4;
+	readcount = devc->limit_samples / 4;
 
 	/* Basic triggers. */
 	struct ols_basic_trigger_desc basic_trigger_desc;