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authorLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-17 02:20:36 +0400
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-17 02:20:36 +0400
commit1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch)
tree0bba044c4ce775e45a88a51686b5d9f90697ea9d /drivers/ieee1394/amdtp.h
downloadlinux-1da177e4c3f41524e886b7f1b8a0c1fc7321cac2.tar.xz
Linux-2.6.12-rc2v2.6.12-rc2
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
Diffstat (limited to 'drivers/ieee1394/amdtp.h')
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diff --git a/drivers/ieee1394/amdtp.h b/drivers/ieee1394/amdtp.h
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+/* -*- c-basic-offset: 8 -*- */
+
+#ifndef __AMDTP_H
+#define __AMDTP_H
+
+#include <asm/types.h>
+#include "ieee1394-ioctl.h"
+
+/* The userspace interface for the Audio & Music Data Transmission
+ * Protocol driver is really simple. First, open /dev/amdtp, use the
+ * ioctl to configure format, rate, dimension and either plug or
+ * channel, then start writing samples.
+ *
+ * The formats supported by the driver are listed below.
+ * AMDTP_FORMAT_RAW corresponds to the AM824 raw format, which can
+ * carry any number of channels, so use this if you're streaming
+ * multichannel audio. The AMDTP_FORMAT_IEC958_PCM corresponds to the
+ * AM824 IEC958 encapsulation without the IEC958 data bit set, using
+ * AMDTP_FORMAT_IEC958_AC3 will transmit the samples with the data bit
+ * set, suitable for transmitting compressed AC-3 audio.
+ *
+ * The rate field specifies the transmission rate; supported values
+ * are 32000, 44100, 48000, 88200, 96000, 176400 and 192000.
+ *
+ * The dimension field specifies the dimension of the signal, that is,
+ * the number of audio channels. Only AMDTP_FORMAT_RAW supports
+ * settings greater than 2.
+ *
+ * The mode field specifies which transmission mode to use. The AMDTP
+ * specifies two different transmission modes: blocking and
+ * non-blocking. The blocking transmission mode always send a fixed
+ * number of samples, typically 8, 16 or 32. To exactly match the
+ * transmission rate, the driver alternates between sending empty and
+ * non-empty packets. In non-blocking mode, the driver transmits as
+ * small packets as possible. For example, for a transmission rate of
+ * 44100Hz, the driver should send 5 41/80 samples in every cycle, but
+ * this is not possible so instead the driver alternates between
+ * sending 5 and 6 samples.
+ *
+ * The last thing to specify is either the isochronous channel to use
+ * or the output plug to connect to. If you know what channel the
+ * destination device will listen on, you can specify the channel
+ * directly and use the AMDTP_IOC_CHANNEL ioctl. However, if the
+ * destination device chooses the channel and uses the IEC61883-1 plug
+ * mechanism, you can specify an output plug to connect to. The
+ * driver will pick up the channel number from the plug once the
+ * destination device locks the output plug control register. In this
+ * case set the plug field and use the AMDTP_IOC_PLUG ioctl.
+ *
+ * Having configured the interface, the driver now accepts writes of
+ * regular 16 bit signed little endian samples, with the channels
+ * interleaved. For example, 4 channels would look like:
+ *
+ * | sample 0 | sample 1 ...
+ * | ch. 0 | ch. 1 | ch. 2 | ch. 3 | ch. 0 | ...
+ * | lsb | msb | lsb | msb | lsb | msb | lsb | msb | lsb | msb | ...
+ *
+ */
+
+enum {
+ AMDTP_FORMAT_RAW,
+ AMDTP_FORMAT_IEC958_PCM,
+ AMDTP_FORMAT_IEC958_AC3
+};
+
+enum {
+ AMDTP_MODE_BLOCKING,
+ AMDTP_MODE_NON_BLOCKING,
+};
+
+enum {
+ AMDTP_INPUT_LE16,
+ AMDTP_INPUT_BE16,
+};
+
+struct amdtp_ioctl {
+ __u32 format;
+ __u32 rate;
+ __u32 dimension;
+ __u32 mode;
+ union { __u32 channel; __u32 plug; } u;
+};
+
+#endif /* __AMDTP_H */