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diff --git a/Documentation/sound/oss/Maestro b/Documentation/sound/oss/Maestro new file mode 100644 index 00000000000..4a80eb3f8e0 --- /dev/null +++ b/Documentation/sound/oss/Maestro @@ -0,0 +1,123 @@ + An OSS/Lite Driver for the ESS Maestro family of sound cards + + Zach Brown, December 1999 + +Driver Status and Availability +------------------------------ + +The most recent version of this driver will hopefully always be available at + http://www.zabbo.net/maestro/ + +I will try and maintain the most recent stable version of the driver +in both the stable and development kernel lines. + +ESS Maestro Chip Family +----------------------- + +There are 3 main variants of the ESS Maestro PCI sound chip. The first +is the Maestro 1. It was originally produced by Platform Tech as the +'AGOGO'. It can be recognized by Platform Tech's PCI ID 0x1285 with +0x0100 as the device ID. It was put on some sound boards and a few laptops. +ESS bought the design and cleaned it up as the Maestro 2. This starts +their marking with the ESS vendor ID 0x125D and the 'year' device IDs. +The Maestro 2 claims 0x1968 while the Maestro 2e has 0x1978. + +The various families of Maestro are mostly identical as far as this +driver is concerned. It doesn't touch the DSP parts that differ (though +it could for FM synthesis). + +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 almost as expected. Playback is +supported in all the various lovely formats. 8/16bit stereo/mono from +8khz to 48khz, and mmap()ing for playback behaves. Capture/recording +is limited due to oddities with the Maestro hardware. One can only +record in 16bit stereo. For recording the maestro uses non interleaved +stereo buffers so that mmap()ing the incoming data does not result in +a ring buffer of LRLR data. mmap()ing of the read buffers is therefore +disallowed until this can be cleaned up. + +/dev/mixer is an interface to the AC'97 codec on the Maestro. It is +worth noting that there are a variety of AC'97s that can be wired to +the Maestro. 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 driver doesn't support MIDI or FM playback at the moment. Typically +the Maestro is wired to an MPU MIDI chip, but some hardware implementations +don't. We need to assemble a white list of hardware implementations that +have MIDI wired properly before we can claim to support it safely. + +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_MAESTRO 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 maestro' +should also be added to your module configs (typically /etc/conf.modules) +if you're using modular OSS/Lite sound and want to default to using a +maestro chip. + +As this is a PCI device, the module does not need to be informed of +any IO or IRQ resources it should use, it devines these from the +system. Sometimes, on sucky PCs, the BIOS fails to allocated resources +for the maestro. This will result in a message like: + maestro: PCI subsystem reports IRQ 0, this might not be correct. +from the kernel. Should this happen the sound chip most likely will +not operate correctly. To solve this one has to dig through their BIOS +(typically entered by hitting a hot key at boot time) and figure out +what magic needs to happen so that the BIOS will reward the maestro with +an IRQ. This operation is incredibly system specific, so you're on your +own. Sometimes the magic lies in 'PNP Capable Operating System' settings. + +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. + +The other, more interesting option, is 'dsps_order'. Typically at +install time the driver will only register one available /dev/dsp device +for its use. The 'dsps_order' module parameter allows for more devices +to be allocated, as a power of two. Up to 4 devices can be registered +( dsps_order=2 ). These devices act as fully distinct units and use +separate channels in the maestro. + +Power Management +---------------- + +As of version 0.14, this driver has a minimal understanding of PCI +Power Management. If it finds a valid power management capability +on the PCI device it will attempt to use the power management +functions of the maestro. It will only do this on Maestro 2Es and +only on machines that are known to function well. You can +force the use of power management by setting the 'use_pm' module +option to 1, or can disable it entirely by setting it to 0. + +When using power management, the driver does a few things +differently. It will keep the chip in a lower power mode +when the module is inserted but /dev/dsp is not open. This +allows the mixer to function but turns off the clocks +on other parts of the chip. When /dev/dsp is opened the chip +is brought into full power mode, and brought back down +when it is closed. It also powers down the chip entirely +when the module is removed or the machine is shutdown. This +can have nonobvious consequences. CD audio may not work +after a power managing driver is removed. Also, software that +doesn't understand power management may not be able to talk +to the powered down chip until the machine goes through a hard +reboot to bring it back. + +.. more details .. +------------------ + +drivers/sound/maestro.c contains comments that hopefully explain +the maestro implementation. |