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home | helpPCM(4) FreeBSD Kernel Interfaces Manual PCM(4) NAME pcm, snd -- FreeBSD PCM audio device driver SYNOPSIS For a card with bridge driver support, and a PnP card: device pcm For a card without bridge driver support, and a non-PnP card: device pcm0 at isa? port? irq 5 drq 1 flags 0x15 DESCRIPTION The pcm driver provides support for PCM audio play and capture. This driver also supports various PCI and WSS/MSS compatible ISA sound cards, and AC97 mixer. True full duplex operation is available on most cards. If your sound card is supported by a bridge driver, pcm driver works in conjunction with the bridge driver. Apart from the usual parameters, the flags field is used to specify the secondary DMA channel (generally used for capture in full duplex cards). Flags are set to 0 for cards not using a secondary DMA channel, or to 0x10 + C to specify channel C. The driver works best with WSS/MSS cards, which have a very clean archi- tecture and an orthogonal set of features. They also happen to be among the cheapest audio cards on the market. The driver does its best to recognize the installed hardware and drive it correctly, so that you don't have to give too many details in the kernel config files. For PCI and ISA PnP cards this is actually easy since they identify themselves. For legacy ISA cards, the driver looks for MSS cards at addresses 0x530 and 0x604 (obviously, unless overridden in the kernel config file by specifying an address). IOCTL The driver supports most of the Voxware ioctls(), and most applications work unmodified (including popular mpeg players and linux binaries). A few differences exist (the most important one is the ability to use mem- ory-mapped access to the audio buffers). As a consequence, some applica- tions may need to be recompiled with a slightly modified audio module. See /usr/include/sys/soundcard.h for a complete list of the supported ioctls. SUPPORTED CARDS Below we include a list of supported codecs/cards. If your sound card is not listed here, it may be supported by a bridge driver. CS4237, CS4236, CS4232, CS4231 (ISA) All these cards work perfectly in full duplex using the MSS mode. This chipset is used, among others, on the A/Open AW35 and AW32, on some Intel motherboards, and (the CS4231) on some non-PnP cards. The CS4232 is reported as buggy in the Voxware documentation but I am not sure if this is true. On one of my Intel motherboards, capture does not work simply because the capture DMA channel is not wired to the ISA DMA controller. Yamaha OPL-SAx (ISA) Works perfectly in all modes. This chip is used in several PnP cards, but also (in non-PnP mode) on motherboards and laptops (e.g. the Toshiba Libretto). OPTi931 (ISA) The chip is buggy, but the driver has many workarounds to make it work in full duplex because for some time these were the only full duplex cards I could find. u-law formats uses U8 format internally because of a bug in the chip. Trident 4DWave DX/NX (PCI) ENSONIQ AudioPCI ES1370/1371 (PCI) Creative Labs SoundBlaster PCI is supported as well. ESS Solo-1/1E (PCI) NeoMagic 256AV/ZX (PCI) FILES The following commonly used symbolic links to real device nodes should be present: /dev/audio Sparc-compatible audio device /dev/dsp Digitized voice device /dev/dspW Like /dev/dsp, but 16 bits per sample /dev/midi Raw midi access device /dev/mixer Control port mixer device /dev/music Level 2 sequencer interface /dev/sequencer Sequencer device /dev/pss Programmable device interface Each symbolic link refers to a device node of the same name, but with a unit number appended. The unit number for each device matches the unit number of the device probed at boot time. Device probe messages can be examined with the dmesg(8) utility. All the appropriate device nodes and symbolic links for the `pcm0' device would created with the following commands: cd /dev; sh MAKEDEV snd0 Similarly, the device nodes and symbolic links for the `pcm1' device would be created as follows: cd /dev; sh MAKEDEV snd1 Since the /dev/MAKEDEV utility creates symbolic links that will be used by many utilities by default, the device nodes and symbolic links for the preferred audio device in systems with multiple audio devices should be created last. DIAGNOSTICS AND TROUBLESHOOTING ac97: dac not ready AC97 codec is not likely to be accompanied with the sound card. unsupported subdevice XX A device node is not created properly. BUGS Some features of your cards (e.g. global volume control) might not be supported on all devices. HISTORY The pcm device driver first appeared in FreeBSD 2.2.6, rewritten in FreeBSD 4.0. SEE ALSO csa(4), gusc(4), sbc(4) AUTHORS Luigi Rizzo <luigi@iet.unipi.it> initially wrote the pcm device driver and this manual page. Cameron Grant <gandalf@vilnya.demon.co.uk> totally revised the device driver. Seigo Tanimura <tanimura@r.dl.itc.u-tokyo.ac.jp> revised this manual page. FreeBSD 7.2 June 3, 1998 FreeBSD 7.2
NAME | SYNOPSIS | DESCRIPTION | IOCTL | SUPPORTED CARDS | FILES | DIAGNOSTICS AND TROUBLESHOOTING | BUGS | HISTORY | SEE ALSO | AUTHORS
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