Legacy audio driver for YMF7xx PCI cards.


FIRST OF ALL
============

  This code references YAMAHA's sample codes and data sheets.
  I respect and thank for all people they made open the informations
  about YMF7xx cards.

  And this codes heavily based on Jeff Garzik <jgarzik@pobox.com>'s
  old VIA 82Cxxx driver (via82cxxx.c). I also respect him.


DISCLIMER
=========

 This driver is currently at early ALPHA stage. It may cause serious
 damage to your computer when used.
 PLEASE USE IT AT YOUR OWN RISK.


ABOUT THIS DRIVER
=================

  This code enables you to use your YMF724[A-F], YMF740[A-C], YMF744, YMF754
 cards as "SoundBlaster Pro" compatible card. It can only play 22.05kHz /
 8bit / Stereo samples, control external MIDI port.
 And it can handle AC'97 mixer of these cards.

  If you want to use your card as recent "16-bit" card, you should use
 Alsa or OSS/Linux driver. Ofcource you can write native PCI driver for
 your cards :)


INSTALL
=======

  First, it requires some sound driver modules in Linux kernel 
 (soundcore.o , sound.o, sb.o and uart401.o), so you should enable
 these modules at kernel configuration (please refer some other 
 documentations for configuration of kernel).
 And add the following line in /etc/modules.conf:

  options sb support=1

 (NOTE: There are no need any configuration of sb modules)

 To compile ymfsb module, type 'make'.
 And copy it to /lib/modules/(kernel_version)/misc, type 'depmod -a'.
 
  This module also requires /usr/src/linux/drivers/sound/ac97.[ch].
 If your kernel doesn't have these files, you should upgrade your kernel.


USAGE
=====

 # modprobe ymfsb (options)


OPTIONS FOR YMFSB
=================

  io           : SB base address     (0x220, 0x240, 0x260, 0x280)
  synth_io     : OPL3 base address   (0x388, 0x398, 0x3a0, 0x3a8)
  dma          : DMA number          (0,1,3)
  spdif_out    : SPDIF-out flag      (0:disable 1:enable)

 These options will change in future...


FREQUENCY
=========

  When playing sounds via this driver, you will hear its pitch is slightly
 lower than original sounds. Since this driver recognizes your card acts
 with 21.739kHz sample rates rather than 22.050kHz (I think it must be
 hardware restriction). So many players become tone deafness.
 To prevent this, you should express some options to your sound player
 that specify correct sample frequency. For example, to play your MP3 file
 correctly with mpg123, specify the frequency like following:

  %  mpg123 -r 21739 foo.mp3


SPDIF OUT
=========

  With installing modules with option 'spdif_out=1', you can enjoy your
 sounds from SPDIF-out of your card (if it had).
 Its Fs is fixed to 48kHz (It never means the sample frequency become 
 up to 48kHz. All sounds via SPDIF-out also 22kHz samples). So your
 digital-in capable components has to be able to handle 48kHz Fs.


COPYING
=======

 This program is free software; you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation; either version 2, or (at your option)
 any later version.

 This program is distributed in the hope that it will be useful, but
 WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 General Public License for more details.

 You should have received a copy of the GNU General Public License
 along with this program; if not, write to the Free Software
 Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.


TODO
====
 * support for multiple cards
   (set the different SB_IO,MPU_IO,OPL_IO for each cards)

 * support for OPL (dmfm) : There will be no requirements... :-<


AUTHOR
======

 Daisuke Nagano <breeze.nagano@nifty.ne.jp>

