ASoC: SOF: ipc4-topology: Allow bytes controls without initial payload

[ujfalusi]

It is unexpected, but allowed to have no initial payload for a bytes control and the code is prepared to handle this case, but the size check missed this corner case.

Update the check fro minimal size to allow the initial size to be 0.

Cc: stable@vger.kernel.org
Fixes: a653820 ("ASoC: SOF: ipc4-topology: Correct the allocation size for bytes controls")

[Copilot]

Pull request overview

This PR adjusts the IPC4 SOF topology bytes-control loader to accept bytes controls that have no initial private payload, matching the stated topology constraints and the driver’s intended handling of “no initial data” cases.

Changes:

• Relax the minimum-size validation so priv_size == 0 is permitted for bytes controls (previously rejected as “insufficient”).

Comments suppressed due to low confidence (1)

sound/soc/sof/ipc4-topology.c:2978

• Allowing priv_size == 0 here means we can allocate a bytes control with an all-zero sof_abi_hdr in control_data->data (kzalloc). Later code uses data->type to build msg->extension (e.g., control_load_bytes() itself sets msg->extension from control_data->data->type, and bytes_ext_volatile_get() / refresh paths call sof_ipc4_set_get_bytes_data() / sof_ipc4_refresh_bytes_control() which also rely on data->type). With type left at 0, GET operations can send an invalid param_id (0) and user-visible reads may return an uninitialized ABI header (magic/type/abi all zero). Consider initializing the ABI header fields when priv_size==0 (at least magic and a valid type/param_id if it can be derived), and/or gating GET/refresh paths to avoid issuing IPC until a valid type is known.

	if (scontrol->priv_size && scontrol->priv_size < sizeof(struct sof_abi_hdr)) {
		dev_err(sdev->dev,
			"bytes control %s initial data size %zu is insufficient.\n",
			scontrol->name, scontrol->priv_size);
		return -EINVAL;

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[kv2019i]

Typo in commit message (s/fro/for), otherwise looks good.

[singalsu]

I tried removed bytes control initialization, got a topology parse fail, while with this patch it didn't happen.