[alsa-devel] plughw, access modes

Nenad Sljivic nenad.sljivic at rt-rk.com
Tue Feb 15 00:44:46 CET 2011


Thanks a lot for your prompt reply, but as far as I see, mmap_emulation flag
is not supported anymore. 
I am using 1.0.19 version of alsa-lib.

1) Should I use mmap_emul plugin instead of it? I haven't been able to find
any example or configuration that's using this plugin

2)  Additional to that, do I have to set SNDRV_PCM_INFO_MMAP in my device
driver, in order for mmap emulation to work?

Sorry for my ignorance, but I am an extreme newbie in this area so any help
is greatly appreciated.

Thanks a lot,

-----Original Message-----
From: Jaroslav Kysela [mailto:perex at perex.cz] 
Sent: 14 February 2011 03:10
To: Nenad Sljivic
Cc: alsa-devel at alsa-project.org
Subject: Re: [alsa-devel] plughw, access modes

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
> access and the data is copied using the copy file operation. My HW
> 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
> file
> " aplay: set_params:1022: Unable to install hw params: "
> My debugging session proved me that plughw device is trying to access
> 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