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.
