Hans-Christian Egtvedt wrote:
Okay, so to be sure I setup and release my cyclic DMA buffer safely I could use the following model:
in prepare callback setup the DMA buffer, once when called. The hardware parameters should not change at this point.
If I get a hw_params callback after a prepare, then release the DMA buffer, and set it up again in the prepare callback?
Final cleanup of the DMA buffer can/should be done in hw_free?
This would work, but doing it in the hw_params callback would be a little more simple: * In hw_params, free the old buffer (if it exists), then setup the buffer; * in hw_free, free the buffer.
As a rule of thumb, the callbacks open/close, hw_params/hw_free and start/stop trigger are mostly symmetrical, and any resources should be allocated and freed in the functions that belong together. (The start trigger is a special case because it uses two callbacks, prepare and trigger with TRIGGER_START.)
The hw_params and prepare callbacks can be called multiple times.
Is there a flow chart which shows how the different callbacks can be called?
Not yet.
Best regards, Clemens