usb_ac(7D) (man pages section 7: Device and Network Interfaces)

man pages section 7: Device and Network Interfaces

usb_ac(7D)

NAME

usb_ac- USB audio control driver

SYNOPSIS

sound-control@unit-address

DESCRIPTION

The usb_ac driver is a USBA (Solaris USB Architecture) compliant client driver that supports the USB Audio Class 1.0 specification.

The audio control driver is a USB class driver and offers functionality similar to the audiocs (sun4u) and audiots (Sun Blade 100) drivers which use the Solaris audio mixer framework (mixer(7I)). Unlike the audiocs and audiots drivers, the USB audio device may have play-only or record-only capability.

Drivers corresponding to other USB audio interfaces on the device, including the usb_as(7D) audio streaming driver or the hid(7D) driver, are plumbed under the USB audio control driver and do not directly interface with user applications.

The usb_ac driver supports USB audio class compliant devices with a feature unit. For a list of recommended devices, visit: www.sun.com/io.

APPLICATION PROGRAM INTERFACE

This interface is described in the mixer(7I) and audio(7I) man pages.

Driver Versions

Applications that open /dev/audio may use the AUDIO_GETDEV ioctl() to determine which audio device is being used. The USB audio driver returns the string "USB Audio" in the name field of the audio_device structure. The version field displays the version number and the config field displays the string "external."

The USB audio device provides support for an external speaker and microphone.

Audio Mixer Mode

The configuration file /kernel/drv/usb_ac.conf is used to configure the USB audio driver and determines whether the audio mixer is enabled or disabled. See the mixer(7I) manual page for details. You can change the audio mixer mode at any time by using the mixerctl(1) or sdtaudiocontrol(1) applications.

Audio Data Formats

The USB audio device supports the audio data formats shown below. Please note that at a minimum, the device must support a sampling frequency of 44100 Hz or 48000 Hz. In the table below, mode "M" indicates that mixer mode is enabled, while "C" indicates that mixer mode is disabled or in compatibility mode.

Sample Rate	Encoding	Precision	Channels	Mode
8000 Hz	u-Law or A-Law	8	1 or 2	M and C
9600 Hz	u-Law or A-Law	8	1 or 2	M and C
11025 Hz	u-law or A-law	8	1 or 2	M and C
16000 Hz	u-law or A-law	8	1 or 2	M and C
18900 Hz	u-law or A-law	8	1 or 2	M and C
22050 Hz	u-law or A-law	8	1 or 2	M and C
32000 Hz	u-law or A-law	8	1 or 2	M and C
33075 Hz	u-law or A-law	8	1 or 2	M and C
37800 Hz	u-law or A-law	8	1 or 2	M and C
44100 Hz	u-law or A-law	8	1 or 2	M and C
48000 Hz	u-law or A-law	8	1 or 2	M and C
8000 Hz	linear	8 or 16	1 or 2	M and C
9600 Hz	linear	8 or 16	1 or 2	M and C
11025 Hz	linear	8 or 16	1 or 2	M and C
16000 Hz	linear	8 or 16	1 or 2	M and C
18900 Hz	linear	8 or 16	1 or 2	M and C
22050 Hz	linear	8 or 16	1 or 2	M and C
32000 Hz	linear	8 or 16	1 or 2	M and C
33075 Hz	linear	8 or 16	1 or 2	M and C
37800 Hz	linear	8 or 16	1 or 2	M and C
44100 Hz	linear	8 or 16	1 or 2	M and C
48000 Hz	linear	8 or 16	1 or 2	M and C

Audio Status Change Notification

As described in the audio(7I) and mixer(7I) man pages, it is possible to request asynchronous notification of changes in the state of an audio device.

ERRORS

If a device is hot-removed while it is active, all subsequent opens will return EIO. All other errors are defined in the audio(7I) man page.

FILES

/kernel/drv/usb_ac: 32 bit ELF kernel module.
/kernel/drv/sparcv9/usb_ac: 64 bit ELF kernel module.
/kernel/drv/usb_ac.conf: USB audio driver configuration file.
/dev/audio: Symlink to the system's primary audio device, not necessarily a USB audio device.
/dev/audioctl: /dev/audio control device.
/dev/sound/[0-N]: Represents the audio devices on the system and is not necessarily a USB audio device.
/dev/sound/[0-N]ctl: /dev/sound audio control device.

ATTRIBUTES

See attributes(5) for descriptions of the following attributes:

ATTRIBUTE TYPE	ATTRIBUTE VALUE
Architecture	PCI-based systems
Availability	SUNWusb, SUNWusbx
Stability level	Evolving

DIAGNOSTICS

In addition to being logged, the following messages may appear on the system console. All messages are formatted in the following manner:

Warning: <device path> (usb_ac<instance num>): Error Message...

Failure to plumb audio streams drivers.: The usb audio streaming driver or the hid driver could not be plumbed under the audio control driver and the device is not usable.
Device was disconnected while open. Data may have been lost.: The device was hot-removed or powered off while it was open and a possible data transfer was in progress. The job was aborted.
Cannot access device. Please reconnect <name>.: There was an error in accessing the device during reconnect. Please reconnect the device.
Device is not identical to the previous one on this port. Please disconnect and reconnect.: A USB audio device was hot-removed while open. A new device was hot-inserted which is not identical to the original USB audio device. Please disconnect the USB device and reconnect the device to the same port.
Busy device has been reconnected.: A device that was hot-removed from a USB port has been re-inserted again.

NOTES

The USB audio device will be power managed if the device is idle.

USB audio devices do not have line out or port control.

If a USB audio device is hot-removed while active, it prints a console warning message requesting you to put the device back in the same port and informing you that there may be data loss. Hot-removal of an active audio device is strongly discouraged.

Close all applications before hot-removing or hot-inserting a device. If an application is open when a device is hot-removed, inserting the device in a different port will create new /dev/sound links but /dev/audio will not be affected. Hotplugging an active device is not recommended.

On slower IA machines and with higher frequency sample rates, you may encounter some audio quality problems.

To make a USB audio device the primary audio device (for example: /dev/audio), close all audio applications, disconnect all USB audio devices, modunload all other audio drivers and then simply reconnect the USB audio device. This will cause /dev/audio to point to the USB audio /dev/sound entry.

Most Solaris audio applications and 3rd party audio applications available on Solaris work well with USB audio devices. For details of the application behavior with USB audio devices, visit www.sun.com/io.

SunOS 5.9 Last Revised 28 Dec 2001