[alsa-devel] PATCH[1/1] Add I2S common driver for Intel MID platform

[Le Gall, Louis]

Hi,
        This patch set is for new I2S SSP common driver that supports I2S audio on Intel MID platforms.

        It is used for sending/receving I2S audio samples on Intel MID platform.

        This interface is mostly used on Intel MID platforms and provide the low level interface for some upper layer drivers such as Alsa sound card driver for Bluetooth/FM peripherals, char device interfaces for modem (cmt_speech),...
        As this is used to transfer speech frames from/to cellular modem that have specific timing constraints (and modem also uses the I2S path to send some side-info), the Alsa SoC interface cannot be used.
        It is based on low level part of cmt_speech driver that can be found in N900 (see http://lists.meego.com/pipermail/meego-kernel/2010-September/000078.html ). The intel_mid_i2s have been separated from cmt_speech in order to be more generic and to be used on other ports (for instance, to provide Alsa sound card driver for Bluetooth and FM).
        Upper level drivers cmt_speech and Alsa sound card driver that uses intel_mid_i2s will be up-streamed in coming days and is planned to use the same folder path (sound/pci/intel_mid_i2s/). So once these files will be upstream, this will provides Alsa sound driver interface for Bluetooth and FM for Intel Mid platform, and specific speech audio interface (char device) that is used by lib cmt speech data.

        I will provide soon some draft version of example driver that uses intel_mid_i2s so reviewers can have better understanding of how it is used and how it fits together.

Best Regards,
Louis Le Gall


Here is a simple diagram that explain where is the intel_mid_i2s in software architecture.

             +-----------+
             |           |
             |Pulse Audio|
             |           |
             |           |
             +-----------+
                   |
                   |
      +------------+------------+
      |                         |
      |                         |
      |                         |
+-----------+             +-----------+
|           |             |Lib cmt    |
|Alsa Lib   |------+      |speech     |------+
|           |      |      |data       |      |
|           |      |      |           |      |
+-----------+      |      +-----------+      |
      |            |                         |
      |            |                         |                          User
......|............|.........................|.................................
      |            |                         |                         Kernel
      |            |                         |
      |            |                         |
      |            |                         |
      |            |                         |
      |            |                         |
      |            |                         |
     \|/          \|/                       \|/
      V            V                         V
+---------+  ++---------++             ++---------++
|         |  ||Alsa snd ||             ||cmt      ||
|Intel SST|  ||driver   ||             ||speech   ||
| "MAD"   |  ||SSP      ||             ||driver   ||
|         |  ||BT/FM    ||             ||         ||
+---------+  ++---------++             ++---------++
      |            |                         |
      |            |                         |
      |            |                         |
      |            |                         |
     \|/           |                        \|/
      V            |                         V
+-----------+      |                   ++---------++
|           |      |                 \ ||intel mid||
|LPE        |      +------------------>||i2s      ||
|           |                        / ||unified  ||
|           |                          ||driver   ||
+-----------+                          ++---------++
      |                                      |
      |                                      |                         Kernel
......|......................................|.................................
      |                                      |                        Hardware
     \|/                                    \|/
      V                                      V
+--       --+                          +--       --+
|           |                          |           |
|MISC       |                          |SSP in I2S |
|           |                          |config     |
|           |                          |           |
+--       --+                          +--       --+