Hans-Christian Egtvedt wrote: > I wonder if I must take care handling changes in DMA address, number of > periods and period size in the prepare callback? > > Or are these locked after the first time prepare is called? The hardware parameters like buffer/period size and sample format are set by calling the hw_params callback; they are valid until a call to hw_free (or another call to hw_params), which doesn't happen while the stream is running. The DMA address is selected by the driver in the hw_params callback, but most drivers let the framework handle this by calling snd_pcm_lib_malloc_pages(). The prepare and start/stop trigger callbacks are called only between hw_params/hw_free, but they could be called multiple times, so you should handle this stuff in the prepare callback only if your device requires that this is done every time before a stream is started. Best regards, Clemens _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
