[alsa-devel] LSI HDA Modem is not working on HP new Laptop which has IDT 7605 HDA codec and REDHAT installed on it with ALSA ver 1.0.24.

[Takashi Iwai]

At Thu, 29 Sep 2011 12:42:41 +0530,
Gupta, Suresh wrote:
> 
> LSI Modem always checks the "opened" bit of "azx_dev" before opening the stream. Modem sets "opened" bit and 
> use stream if and only if that "opened" bit was not set otherwise move to next stream "azx_dev".
> 
> I found that the ALSA unset this "opened" bit on close but do not reset  AC_VERB_SET_CHANNEL_STREAMID of IDC codec. 
> Due to which IDC Codec always get active and always sending data to stream 0. Now when LSI modem check the "opened" 
> bit of stream 0, it found it is not set and open the stream 0 and start reading data from stream 0. As IDC codec 
> still sending data on stream 0 the LSI Modem get this unexpected data and stop working.
>   
> I believe the Code (below) which checks "no_sticky_stream" is the culprit due to which "really_cleanup_stream" 
> function is not called. I found the Analog devices codec set "no_sticky_stream" while probing their codec. 
> This is the reason, our modem works on HP laptop with Analog device codec.
>  
> According to me the IDC codec should stop sending data after closing the stream or otherwise they should always acquire the stream which is not right. 
> 
> I don't know why "no_sticky_stream" come into new code and what's it significance. Why only Analog devices use this "no_sticky_stream".  

The problem is that your driver steals the stream silently.
The stream is still assigned to the IDT codec driver even after the
PCM is closed.  It's just not used.  When the PCM is opened, the very
same stream is used again without reassigning the stream tag.

Now the modem driver grabs the stream and use the stream tag.  Of
course, the data will be fed.  

The stream must be allocated via azx_assign_device().  If you don't,
it's not guaranteed what happens.


Takashi