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+ An OSS/Lite Driver for the ESS Maestro3 family of sound chips
+ Zach Brown, January 2001
+Driver Status and Availability
+The most recent version of this driver will hopefully always be available at
+I will try and maintain the most recent stable version of the driver
+in both the stable and development kernel lines.
+Historically I've sucked pretty hard at actually doing that, however.
+ESS Maestro3 Chip Family
+The 'Maestro3' is much like the Maestro2 chip. The noted improvement
+is the removal of the silicon in the '2' that did PCM mixing. All that
+work is now done through a custom DSP called the ASSP, the Asynchronus
+Specific Signal Processor.
+The 'Allegro' is a baby version of the Maestro3. I'm not entirely clear
+on the extent of the differences, but the driver supports them both :)
+The 'Allegro' shows up as PCI ID 0x1988 and the Maestro3 as 0x1998,
+both under ESS's vendor ID of 0x125D. The Maestro3 can also show up as
+0x199a when hardware strapping is used.
+The chip can also act as a multi function device. The modem IDs follow
+the audio multimedia device IDs. (so the modem part of an Allegro shows
+up as 0x1989)
+Driver OSS Behavior
+This OSS driver exports /dev/mixer and /dev/dsp to applications, which
+mostly adhere to the OSS spec. This driver doesn't register itself
+with /dev/sndstat, so don't expect information to appear there.
+The /dev/dsp device exported behaves as expected. Playback is
+supported in all the various lovely formats. 8/16bit stereo/mono from
+8khz to 48khz, with both read()/write(), and mmap().
+/dev/mixer is an interface to the AC'97 codec on the Maestro3. It is
+worth noting that there are a variety of AC'97s that can be wired to
+the Maestro3. Which is used is entirely up to the hardware implementor.
+This should only be visible to the user by the presence, or lack, of
+'Bass' and 'Treble' sliders in the mixer. Not all AC'97s have them.
+The Allegro has an onchip AC'97.
+The driver doesn't support MIDI or FM playback at the moment.
+Compiling and Installing
+With the drivers inclusion into the kernel, compiling and installing
+is the same as most OSS/Lite modular sound drivers. Compilation
+of the driver is enabled through the CONFIG_SOUND_MAESTRO3 variable
+in the config system.
+It may be modular or statically linked. If it is modular it should be
+installed with the rest of the modules for the kernel on the system.
+Typically this will be in /lib/modules/ somewhere. 'alias sound-slot-0
+maestro3' should also be added to your module configs (typically
+/etc/modprobe.conf) if you're using modular OSS/Lite sound and want to
+default to using a maestro3 chip.
+There are very few options to the driver. One is 'debug' which will
+tell the driver to print minimal debugging information as it runs. This
+can be collected with 'dmesg' or through the klogd daemon.
+One is 'external_amp', which tells the driver to attempt to enable
+an external amplifier. This defaults to '1', you can tell the driver
+not to bother enabling such an amplifier by setting it to '0'.
+And the last is 'gpio_pin', which tells the driver which GPIO pin number
+the external amp uses (0-15), The Allegro uses 8 by default, all others 1.
+If everything loads correctly and seems to be working but you get no sound,
+try tweaking this value.
+Systems known to need a different value
+ Panasonic ToughBook CF-72: gpio_pin=13
+This driver has a minimal understanding of PCI Power Management. It will
+try and power down the chip when the system is suspended, and power
+it up with it is resumed. It will also try and power down the chip
+when the machine is shut down.