Android 2.2-froyo移植之audio系统（freescale i.mx23平台）

基本上参照了http://www.linuxidc.com/Linux/2011-07/39526.htm

kernel部分不需要改动，只需要在Android下面做事情。

1：下载alsa相关代码

cd android/external
git clone git://android.git.kernel.org/platform/external/alsa-lib.git
git clone git://android.git.kernel.org/platform/external/alsa-utils.gitcd ../hardware
git clone git://android.git.kernel.org/platform/hardware/alsa_sound.git

2：修改：build/target/board/generic/BoardConfig.mk 为如下

# config.mk
#
# Product-specific compile-time definitions.
#

# The generic product target doesn"t have any hardware-specific pieces.
TARGET_NO_BOOTLOADER := true
TARGET_NO_KERNEL := true
TARGET_CPU_ABI := armeabi
#HAVE_HTC_AUDIO_DRIVER := true
BOARD_USES_ALSA_AUDIO := true
BUILD_WITH_ALSA_UTILS := true
BOARD_USES_GENERIC_AUDIO := false

# Set /system/bin/sh to mksh, not ash, to test the transition.
TARGET_SHELL := mksh

3：make clean
4：make -j2
5：修改 init.rc，在此文件中加入如下代码，注意，应该在比较靠前的地方。

# windsome modify audio
    chown root audio /dev/snd/controlC0
    chown root audio /dev/snd/pcmC0D0c
    chown root audio /dev/snd/pcmC0D0p
    chown root audio /dev/snd/timer
    chmod 0666 /dev/snd/controlC0
    chmod 0666 audio /dev/snd/pcmC0D0c
    chmod 0666 audio /dev/snd/pcmC0D0p
    chmod 0666 audio /dev/snd/timer

6：增加asound.conf 文件，并放入到system/etc/下。我是从网上抄的一个，稍微改改能用了，也没有仔细分析到底该怎么写。

# #
# # Mixer devices
# #
ctl.AndroidOut {
    type hw
    card 0
}
ctl.AndroidIn {
    type hw
    card 0
}
ctl.AndroidPlayback {
    type hw
    card 0 # Can replace with drivers name from /proc/asound/cards
}
ctl.AndroidRecord {
    type hw
    card 0
}

# #
# # Playback devices
# #
pcm.AndroidPlayback {
    type hw
    card 0
    device 0
}

pcm.AndroidPlayback_Speaker {
                type hw
                card 0
                device 0
}

pcm.AndroidPlayback_Speaker_normal {
                type hw
                card 0
                device 0
}

pcm.AndroidPlayback_Speaker_ringtone {
                type hw
                card 0
                device 0
}

pcm.AndroidPlayback_Speaker_incall {
                type hw
                card 0
                device 0
}

pcm.AndroidPlayback_Earpiece {
                type hw
                card 0
                device 0
}

pcm.AndroidPlayback_Earpiece_normal {
                type hw
                card 0
                device 0
}

pcm.AndroidPlayback_Earpiece_ringtone {
                type hw
                card 0
                device 0
}

pcm.AndroidPlayback_Earpiece_incall {
                type hw
                card 0
                device 0
}

pcm.AndroidPlayback_Bluetooth {
                type hw
                card 0
                device 0
}

pcm.AndroidPlayback_Bluetooth_normal {
                type hw
                card 0
                device 0
}

pcm.AndroidPlayback_Bluetooth_ringtone {
                type hw
                card 0
                device 0
}

pcm.AndroidPlayback_Bluetooth_incall {
                type hw
                card 0
                device 0
}

pcm.AndroidPlayback_Headset {
                type hw
                card 0
                device 0
}

pcm.AndroidPlayback_Headset_normal {
                type hw
                card 0
                device 0
}

pcm.AndroidPlayback_Headset_ringtone {
    type hw
    card 0
    device 0
}

pcm.AndroidPlayback_Headset_incall {
    type hw
    card 0
    device 0
}

pcm.AndroidPlayback_Bluetooth-A2DP {
    type hw
    card 0
    device 0
}

pcm.AndroidPlayback_Bluetooth-A2DP_normal {
    type hw
    card 0
    device 0
}

pcm.AndroidPlayback_Bluetooth-A2DP_ringtone {
    type hw
    card 0
    device 0
}

pcm.AndroidPlayback_Bluetooth-A2DP_incall {
    type hw
    card 0
    device 0
}

pcm.AndroidRecord {
    type hw
    card 0
    device 0
}

pcm.AndroidRecord_Microphone {
                type hw
                card 0
                device 0
}