ASoC: sof: Improve sof_ipc3_bytes_ext_put function

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>
Link: https://lore.kernel.org/r/20230503081049.73847-2-daniel.baluta@oss.nxp.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/sof/ipc3-control.c

@@ -96,6 +96,26 @@ static int sof_ipc3_set_get_kcontrol_data(struct snd_sof_control *scontrol,
 	cdata->elems_remaining = 0;
 
 	ret = iops->set_get_data(sdev, cdata, cdata->rhdr.hdr.size, set);
+	if (!set)
+		goto unlock;
+
+	/* It is a set-data operation, and we have a 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, cdata, cdata->rhdr.hdr.size, set);
+		if (ret < 0)
+			goto unlock;
+	}
 
 unlock:
 	if (lock)
@@ -351,6 +371,7 @@ static int sof_ipc3_bytes_ext_put(struct snd_sof_control *scontrol,
 	struct sof_ipc_ctrl_data *cdata = scontrol->ipc_control_data;
 	struct snd_soc_component *scomp = scontrol->scomp;
 	struct snd_ctl_tlv header;
+	int ret = -EINVAL;
 
 	/*
 	 * The beginning of bytes data contains a header from where
@@ -381,31 +402,52 @@ static int sof_ipc3_bytes_ext_put(struct snd_sof_control *scontrol,
 		return -EINVAL;
 	}
 
-	if (copy_from_user(cdata->data, tlvd->tlv, header.length))
-		return -EFAULT;
+	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;
+	}
+
+	if (copy_from_user(cdata->data, tlvd->tlv, header.length)) {
+		ret = -EFAULT;
+		goto err_restore;
+	}
 
 	if (cdata->data->magic != SOF_ABI_MAGIC) {
 		dev_err_ratelimited(scomp->dev, "Wrong ABI magic 0x%08x\n", cdata->data->magic);
-		return -EINVAL;
+		goto err_restore;
 	}
 
 	if (SOF_ABI_VERSION_INCOMPATIBLE(SOF_ABI_VERSION, cdata->data->abi)) {
 		dev_err_ratelimited(scomp->dev, "Incompatible ABI version 0x%08x\n",
 				    cdata->data->abi);
-		return -EINVAL;
+		goto err_restore;
 	}
 
 	/* be->max has been verified to be >= sizeof(struct sof_abi_hdr) */
 	if (cdata->data->size > scontrol->max_size - sizeof(struct sof_abi_hdr)) {
 		dev_err_ratelimited(scomp->dev, "Mismatch in ABI data size (truncated?)\n");
-		return -EINVAL;
+		goto err_restore;
 	}
 
 	/* notify DSP of byte control updates */
-	if (pm_runtime_active(scomp->dev))
+	if (pm_runtime_active(scomp->dev)) {
+		/* Actually send the data to the DSP; this is an opportunity to validate the data */
 		return sof_ipc3_set_get_kcontrol_data(scontrol, true, true);
+	}
 
 	return 0;
+
+err_restore:
+	/* If we have an issue, we restore the old, valid bytes control data */
+	if (scontrol->old_ipc_control_data) {
+		memcpy(cdata->data, scontrol->old_ipc_control_data, scontrol->max_size);
+		kfree(scontrol->old_ipc_control_data);
+		scontrol->old_ipc_control_data = NULL;
+	}
+	return ret;
 }
 
 static int _sof_ipc3_bytes_ext_get(struct snd_sof_control *scontrol,

sound/soc/sof/sof-audio.h

@@ -362,6 +362,7 @@ struct snd_sof_control {
 	size_t priv_size; /* size of private data */
 	size_t max_size;
 	void *ipc_control_data;
+	void *old_ipc_control_data;
 	int max; /* applicable to volume controls */
 	u32 size;	/* cdata size */
 	u32 *volume_table; /* volume table computed from tlv data*/