[alsa-devel] customized IOCTL in pcm platform driver.

[gsantosh at codeaurora.org]

> At Tue, 9 Oct 2012 00:30:40 -0700 (PDT),
> gsantosh at codeaurora.org wrote:
>>
>> > At Mon, 8 Oct 2012 23:44:40 -0700 (PDT),
>> > gsantosh at codeaurora.org wrote:
>> >>
>> >> > At Mon, 8 Oct 2012 23:30:09 -0700 (PDT),
>> >> > gsantosh at codeaurora.org wrote:
>> >> >>
>> >> >> Hi All,
>> >> >>
>> >> >> will ALSA framework provide any customized IOCTL functionality in
>> PCM
>> >> >> platform driver.
>> >> >
>> >> > No.
>> >> >
>> >> >> in my  system there is a requirement to get some information from
>> DSP
>> >> to
>> >> >> user space and I am thinking to add IOCTL's, is there any method
>> to
>> >> >> accommodate or how we can address this issue?
>> >> >
>> >> > You can use hwdep device for any extra methods.
>> >>
>> >> We need to tie this ioctl with the on going DSP session which will be
>> >> difficult When used with hwdep interface.
>> >
>> > Hm, how can it be difficult?  More specific description is needed to
>> > answer more.
>>
>> to communicate with DSP we open up a session and populate that
>> information
>> in the substream, for this use case during the playback session user
>> space
>> has to talk to DSP to get some information like time stamp also the time
>> stamp statistics, to talk to DSP I need to get hold of the proper
>> substream so that the communication with particular session is possible.
>>
>> I see adding one IOCTL in the platform driver will solve my issue, but
>> not
>> finding any way to integrate this in the current framework,
>>
>> if we use the hwdep, not sure how can I get hold of the substream handle
>> so I can talk to particular session in DSP.
>
> A PCM substream can be identified simply by a PCM device number and
> a PCM substream index.  You can make ioctl to pass these information.
>

Can you point to any code reference doing this operation?
did you mean accessing the sub-stream handle in user space or in the
kernel driver.


>
> Takashi
>