| Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 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 */ |