Re: [PATCH v2] ASoC: SOF: ipc3-topology: Correct get_control_data for non bytes payload

Sergey Senozhatsky
2022-04-27T12:32:16Z

On (22/04/27 15:08), Péter Ujfalusi wrote:
> > clang appears to be unhappy otherwise.
> >
> > error: comparison of array 'cdata->data' equal to a null pointer is always false
> >
> > Changing this into `if (!cdata->data)` is a little bit better as now
> > 'always false' becomes 'always true'
> >
> > error: address of array 'cdata->data' will always evaluate to 'true'
>
> Hrm, uhm. clang is right. The check is (and was) bogus...
>
> cdata->data is a pointer (to cdata->data[0]) which is always:
> cdata + sizeof(struct sof_ipc_ctrl_data).
> Checking if it is NULL or not is irrelevant and wrong. If we do not have
> additional data then cdata->data points to memory which is outside of
> the struct and it can be random data (might be 0, might not be).

Yeah to be honest that's what I'm thinking too.

Does sof_ipc_ctrl_data have to be a var-sized structure? Or can that union
hold pointers that are allocated separately?

scontrol->data = kzalloc(sizeof sof_ipc_ctrl_data);
scontrol->data->chan = kzalloc(sizeof chan * mc->num_channels)

> I think we can just drop this check as we would not be here if
> additional data was not allocated for the payload prior?

I don't have enough knowledge of this code. ->data check doesn't do what
it is expected to do so removing it shouldn't do harm.