[ALSA] some docs for the new emu10k1 multichannel functionality

Documentation
Not complete, or even spell checked, but in case I don't get a chance to
work on it again before 1.0.9, here is what i have so far. It should go
in alsa-kernel/Documentation/emu10k1-jack.txt.

Signed-off-by: Lee Revell <[e-mail]>
Signed-off-by: Takashi Iwai <[e-mail]>

Documentation/sound/alsa/emu10k1-jack.txt

···
+This document is a guide to using the emu10k1 based devices with JACK for low
+latency, multichannel recording functionality.  All of my recent work to allow
+Linux users to use the full capabilities of their hardware has been inspired 
+by the kX Project.  Without their work I never would have discovered the true
+power of this hardware.
+
+	http://www.kxproject.com
+						- Lee Revell, 2005.03.30
+
+Low latency, multichannel audio with JACK and the emu10k1/emu10k2
+-----------------------------------------------------------------
+
+Until recently, emu10k1 users on Linux did not have access to the same low
+latency, multichannel features offered by the "kX ASIO" feature of their
+Windows driver.  As of ALSA 1.0.9 this is no more!
+
+For those unfamiliar with kX ASIO, this consists of 16 capture and 16 playback
+channels.  With a post 2.6.9 Linux kernel, latencies down to 64 (1.33 ms) or
+even 32 (0.66ms) frames should work well.
+
+The configuration is slightly more involved than on Windows, as you have to
+select the correct device for JACK to use.  Actually, for qjackctl users it's
+fairly self explanatory - select Duplex, then for capture and playback select
+the multichannel devices, set the in and out channels to 16, and the sample
+rate to 48000Hz.  The command line looks like this:
+
+/usr/local/bin/jackd -R -dalsa -r48000 -p64 -n2 -D -Chw:0,2 -Phw:0,3 -S
+
+This will give you 16 input ports and 16 output ports.
+
+The 16 output ports map onto the 16 FX buses (or the first 16 of 64, for the
+Audigy).  The mapping from FX bus to physical output is described in
+SB-Live-mixer.txt (or Audigy-mixer.txt).
+
+The 16 input ports are connected to the 16 physical inputs.  Contrary to
+popular belief, all emu10k1 cards are multichannel cards.  Which of these
+input channels have physical inputs connected to them depends on the card
+model.  Trial and error is highly recommended; the pinout diagrams
+for the card have been reverse engineered by some enterprising kX users and are 
+available on the internet.  Meterbridge is helpful here, and the kX forums are
+packed with useful information.
+
+Each input port will either correspond to a digital (SPDIF) input, an analog
+input, or nothing.  The one exception is the SBLive! 5.1.  On these devices,
+the second and third input ports are wired to the center/LFE output.  You will
+still see 16 capture channels, but only 14 are available for recording inputs.
+
+This chart, borrowed from kxfxlib/da_asio51.cpp, describes the mapping of JACK
+ports to FXBUS2 (multitrack recording input) and EXTOUT (physical output)
+channels.
+
+/*JACK (& ASIO) mappings on 10k1 5.1 SBLive cards:
+--------------------------------------------
+JACK		Epilog		FXBUS2(nr)
+--------------------------------------------
+capture_1	asio14		FXBUS2(0xe)
+capture_2	asio15		FXBUS2(0xf)
+capture_3	asio0		FXBUS2(0x0)	
+~capture_4	Center		EXTOUT(0x11)	// mapped to by Center
+~capture_5	LFE		EXTOUT(0x12)	// mapped to by LFE
+capture_6	asio3		FXBUS2(0x3)
+capture_7	asio4		FXBUS2(0x4)
+capture_8	asio5		FXBUS2(0x5)
+capture_9	asio6		FXBUS2(0x6)
+capture_10	asio7		FXBUS2(0x7)
+capture_11	asio8		FXBUS2(0x8)
+capture_12	asio9		FXBUS2(0x9)
+capture_13	asio10		FXBUS2(0xa)
+capture_14	asio11		FXBUS2(0xb)
+capture_15	asio12		FXBUS2(0xc)
+capture_16	asio13		FXBUS2(0xd)
+*/
+
+TODO: describe use of ld10k1/qlo10k1 in conjunction with JACK