[PATCH 2/2] ASoC: sof: Improve sof_ipc4_bytes_ext_put function

[Daniel Baluta <daniel.baluta@oss.nxp.com>]

From: Paul Olaru <paul.olaru@nxp.com>

The function is improved in the way that if the firmware returns a
validation error on the newly sent bytes, then the kernel will
automatically restore to the old bytes value for a given kcontrol.

This way, if the firmware rejects a data blob then the kernel will also
reject it, instead of saving it for the next suspend/resume cycle. The
old behaviour is that the kernel would save it anyway and on next
firmware boot it would apply the previously-rejected configuration,
leading to errors during playback.

Additionally, the function also saves previously validated
configurations, so that if the firmware does end up rejecting a new
bytes value the kernel can send an old, previously-valid configuration.

Reviewed-by: Daniel Baluta <daniel.baluta@nxp.com>
Reviewed-by: Péter Ujfalusi <peter.ujfalusi@linux.intel.com>
Signed-off-by: Paul Olaru <paul.olaru@nxp.com>
Signed-off-by: Daniel Baluta <daniel.baluta@nxp.com>

---
 sound/soc/sof/ipc4-control.c | 39 ++++++++++++++++++++++++++++++++----
 1 file changed, 35 insertions(+), 4 deletions(-)

diff --git a/sound/soc/sof/ipc4-control.c b/sound/soc/sof/ipc4-control.c
index 6f0698be9451..c6d404d44097 100644
--- a/sound/soc/sof/ipc4-control.c
+++ b/sound/soc/sof/ipc4-control.c
@@ -54,6 +54,26 @@ static int sof_ipc4_set_get_kcontrol_data(struct snd_sof_control *scontrol,
 	msg->primary |= SOF_IPC4_MOD_INSTANCE(swidget->instance_id);
 
 	ret = iops->set_get_data(sdev, msg, msg->data_size, set);
+	if (!set)
+		goto unlock;
+
+	/* It is a set-data operation, and we have a valid backup that we can restore */
+	if (ret < 0) {
+		if (!scontrol->old_ipc_control_data)
+			goto unlock;
+		/*
+		 * Current ipc_control_data is not valid, we use the last known good
+		 * configuration
+		 */
+		memcpy(scontrol->ipc_control_data, scontrol->old_ipc_control_data,
+		       scontrol->max_size);
+		kfree(scontrol->old_ipc_control_data);
+		scontrol->old_ipc_control_data = NULL;
+		/* Send the last known good configuration to firmware */
+		ret = iops->set_get_data(sdev, msg, msg->data_size, set);
+		if (ret < 0)
+			goto unlock;
+	}
 
 unlock:
 	if (lock)
@@ -327,13 +347,24 @@ static int sof_ipc4_bytes_ext_put(struct snd_sof_control *scontrol,
 		return -EINVAL;
 	}
 
+	if (!scontrol->old_ipc_control_data) {
+		/* Create a backup of the current, valid bytes control */
+		scontrol->old_ipc_control_data = kmemdup(scontrol->ipc_control_data,
+							 scontrol->max_size, GFP_KERNEL);
+		if (!scontrol->old_ipc_control_data)
+			return -ENOMEM;
+	}
+
 	/* Copy the whole binary data which includes the ABI header and the payload */
-	if (copy_from_user(data, tlvd->tlv, header.length))
+	if (copy_from_user(data, tlvd->tlv, header.length)) {
+		memcpy(scontrol->ipc_control_data, scontrol->old_ipc_control_data,
+		       scontrol->max_size);
+		kfree(scontrol->old_ipc_control_data);
+		scontrol->old_ipc_control_data = NULL;
 		return -EFAULT;
+	}
 
-	sof_ipc4_set_get_bytes_data(sdev, scontrol, true, true);
-
-	return 0;
+	return sof_ipc4_set_get_bytes_data(sdev, scontrol, true, true);
 }
 
 static int _sof_ipc4_bytes_ext_get(struct snd_sof_control *scontrol,
-- 
2.25.1