[alsa-devel] Is params_format() valid in the _hw_params() function?

My ASoC driver programs the sample size in the _prepare() callback function, because I was under the impression that the sample size cannot be known in the _hw_params() callback function. However, I just ran a test, and it appears that the params_format() macro does return the right value. Once I know the format, I can determine the same size.

Is this always true, even in OSS emulation? I know very little about ALSA and OSS application programming, so I don't know what causes _hw_params() to be called vs. _prepare(). If it turns out that params_format() does work in _hw_params(), I can greatly simplify my driver.