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