[alsa-devel] plughw, access modes

Nenad Sljivic nenad.sljivic at rt-rk.com
Mon Feb 14 12:04:27 CET 2011

Greetings guys,


I am dealing with the device driver for the chip that has his own hardware
buffer and the DMA is not available. Therefore, driver doesn't support MMAP
access and the data is copied using the copy file operation. My HW natively
supports BE format. 

However, I would like to be able to play little endian pcm as well. 

The problem, occurs when I try to use plughw device in order to play LE pcm


" aplay: set_params:1022: Unable to install hw params: "


My debugging session proved me that plughw device is trying to access device
driver with MMAP_INTERLEAVED mode. Does it mean that this is the only way
for plughw to access device driver, and that I am not able to use plugins
unless do some heavy modifications of device drivers (implement mmap
access). Am I missing something?

Any info on this would be most welcome.






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