There is a problem with snd_soc_dai_set_fmt():
int snd_soc_dai_set_fmt(struct snd_soc_dai *dai, unsigned int fmt) { if (dai->driver && dai->driver->ops->set_fmt) return dai->driver->ops->set_fmt(dai, fmt); else return -EINVAL; }
Let's say the DAI driver has not defined a .set_fmt() function. This means that if the fabric driver does this:
ret = snd_soc_dai_set_fmt(cpu_dai, machine_data->dai_format); if (ret < 0) { dev_err(dev, "could not set CPU driver audio format\n"); return ret; }
It's going to think that the DAI driver *rejected* the DAI format. What this means is that I cannot make this function optional. I have to define this function in my CPU driver.
May I propose this:
int snd_soc_dai_set_fmt(struct snd_soc_dai *dai, unsigned int fmt) { if (dai->driver && dai->driver->ops->set_fmt) return dai->driver->ops->set_fmt(dai, fmt); else return 0; }