drivers/ieee1394/amdtp.h

   1 /* -*- c-basic-offset: 8 -*- */
   2
   3 #ifndef __AMDTP_H
   4 #define __AMDTP_H
   5
   6 #include <asm/types.h>
   7 #include "ieee1394-ioctl.h"
   8
   9 /* The userspace interface for the Audio & Music Data Transmission
  10  * Protocol driver is really simple. First, open /dev/amdtp, use the
  11  * ioctl to configure format, rate, dimension and either plug or
  12  * channel, then start writing samples.
  13  *
  14  * The formats supported by the driver are listed below.
  15  * AMDTP_FORMAT_RAW corresponds to the AM824 raw format, which can
  16  * carry any number of channels, so use this if you're streaming
  17  * multichannel audio.  The AMDTP_FORMAT_IEC958_PCM corresponds to the
  18  * AM824 IEC958 encapsulation without the IEC958 data bit set, using
  19  * AMDTP_FORMAT_IEC958_AC3 will transmit the samples with the data bit
  20  * set, suitable for transmitting compressed AC-3 audio.
  21  *
  22  * The rate field specifies the transmission rate; supported values
  23  * are 32000, 44100, 48000, 88200, 96000, 176400 and 192000.
  24  *
  25  * The dimension field specifies the dimension of the signal, that is,
  26  * the number of audio channels.  Only AMDTP_FORMAT_RAW supports
  27  * settings greater than 2.
  28  *
  29  * The mode field specifies which transmission mode to use. The AMDTP
  30  * specifies two different transmission modes: blocking and
  31  * non-blocking.  The blocking transmission mode always send a fixed
  32  * number of samples, typically 8, 16 or 32.  To exactly match the
  33  * transmission rate, the driver alternates between sending empty and
  34  * non-empty packets.  In non-blocking mode, the driver transmits as
  35  * small packets as possible.  For example, for a transmission rate of
  36  * 44100Hz, the driver should send 5 41/80 samples in every cycle, but
  37  * this is not possible so instead the driver alternates between
  38  * sending 5 and 6 samples.
  39  *
  40  * The last thing to specify is either the isochronous channel to use
  41  * or the output plug to connect to.  If you know what channel the
  42  * destination device will listen on, you can specify the channel
  43  * directly and use the AMDTP_IOC_CHANNEL ioctl.  However, if the
  44  * destination device chooses the channel and uses the IEC61883-1 plug
  45  * mechanism, you can specify an output plug to connect to.  The
  46  * driver will pick up the channel number from the plug once the
  47  * destination device locks the output plug control register.  In this
  48  * case set the plug field and use the AMDTP_IOC_PLUG ioctl.
  49  *
  50  * Having configured the interface, the driver now accepts writes of
  51  * regular 16 bit signed little endian samples, with the channels
  52  * interleaved.  For example, 4 channels would look like:
  53  *
  54  *   | sample 0                                      | sample 1    ...
  55  *   | ch. 0     | ch. 1     | ch. 2     | ch. 3     | ch. 0     | ...
  56  *   | lsb | msb | lsb | msb | lsb | msb | lsb | msb | lsb | msb | ...
  57  *
  58  */
  59
  60 enum {
  61         AMDTP_FORMAT_RAW,
  62         AMDTP_FORMAT_IEC958_PCM,
  63         AMDTP_FORMAT_IEC958_AC3
  64 };
  65
  66 enum {
  67         AMDTP_MODE_BLOCKING,
  68         AMDTP_MODE_NON_BLOCKING,
  69 };
  70
  71 enum {
  72         AMDTP_INPUT_LE16,
  73         AMDTP_INPUT_BE16,
  74 };
  75
  76 struct amdtp_ioctl {
  77         __u32 format;
  78         __u32 rate;
  79         __u32 dimension;
  80         __u32 mode;
  81         union { __u32 channel; __u32 plug; } u;
  82 };
  83
  84 #endif /* __AMDTP_H */