[alsa-devel] plughw, access modes

Jaroslav Kysela perex at perex.cz
Mon Feb 14 12:09:57 CET 2011

On Mon, 14 Feb 2011, Nenad Sljivic wrote:

> 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
> file
> " 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?

You may enable mmap_emulation for the hw: plugin - see mmap_emulation in:



Jaroslav Kysela <perex at perex.cz>
Linux Kernel Sound Maintainer
ALSA Project, Red Hat, Inc.

More information about the Alsa-devel mailing list