Template Version: @(#)sac_nextcase 1.68 02/23/09 SMI
This information is Copyright 2009 Sun Microsystems
1. Introduction
1.1. Project/Component Working Name:
/etc/audio_numbers
1.2. Name of Document Author/Supplier:
Author: Garrett D'Amore
1.3 Date of This Document:
23 November, 2009
4. Technical Description
Summary:
This case introduces a new project-private statefile for the Boomer
(PSARC 2008/318) audio subsystem. The file will be shared between the
kernel and userland. This will replace the system/device/audio:default
SMF service, so that no other startup service will be necessary.
These changes are necessary to properly address CR 6902551 (audio service
timeout not sufficient for service to start).
Binding:
This case seeks Minor binding.
Problem:
Due to the way the Open Sound System API was originally specified (designed
for Linux), we have to know the "number" of an audio device (e.g. /dev/dsp1
would be "1") in the kernel, because these numbers are reported back from
the kernel to userland via ioctls.
The problem is that the enumeration of these numbers is done entirely in user
space by devfsadm.
Currently, we regenerate this information and send it down at each boot by
performing a devfsadm operation during boot using an SMF service. However,
it turns out that devfsadm on some systems is quite expensive, and this can
lead to timeouts in the audio SMF service
Solution:
We propose to move from regenerating this state (and autoconfiguring each
device driver) at boot, and instead use a persistent state file to track
this information.
The state file will be called "/etc/audio_numbers", and will be written by
devfsadm when it creates an audio link. The contents will be lines that
have the form
number<ws>driver<ws>instance<newline>
<ws> is a sequence of one or more tabs or space characters.
<newline> is an ASCII newline character.
"number" will be the enumerated audio device number in decimal, i.e. the
suffix of the /dev/dspXX or /dev/audioXX link. (Also /dev/sound/XX, etc.)
The "driver" is the name of the audio driver, e.g. "audiohd".
The "instance" is the audio instance number. This will normally be the same
as the device instance (i.e. as from ddi_get_instance()), but for some devices
it could be a different value. (E.g. for a multiport device there could be
multiple logical audio device instances per dev_info_t. The actual value
is the 2nd argument to audio_dev_alloc(9F) specified in Boomer, unless that
value is zero, in which case the ddi_get_instance() value is assumed.)
Lines beginning with a hash mark (#) are treated as comments.
Here is an example file:
# Sample file - this is a comment
0 audiohd 0
1 usb_ac 0
2 audiosolo 0
3 audiosolo 1
4 usb_ac 1
The /etc/audio_number file and its contents shall be deemed Project Private.
The devfsadm audio link module will cease its traversal of the /dev tree,
and instead rely on the statefile to determine suitable targets for symbolic
links.
Finally, we will be able remove the SMF facility sys/devices/audio, which
is currently used to regenerate the state information on each boot.
This project will need to import the kobj interfaces for reading a file from
kernel space. While there is no case work behind these interfaces, we believe
they are Consolidation Private based on existing contracts for their use
from the Sun Cluster products.
Imported Interfaces
kobj_open_file() Consolidation Private
kobj_close_file() " "
kobj_getc() " "
Exported Interfaces
svc:/system/device/audio:default EOF
/etc/audio_numbers Project Private
6. Resources and Schedule
6.4. Steering Committee requested information
6.4.1. Consolidation C-team Name:
ON
6.5. ARC review type: FastTrack
6.6. ARC Exposure: open
