control调用流程

最新推荐文章于 2022-03-19 23:53:14 发布

zll5258

最新推荐文章于 2022-03-19 23:53:14 发布

阅读量1k

点赞数

分类专栏： audio 文章标签： audio

本文链接：https://blog.youkuaiyun.com/zll5258/article/details/53099440

版权

audio 专栏收录该内容

3 篇文章

订阅专栏

这篇博客详细阐述了音频控制的流程，从内核部分的control控制codec寄存器操作，包括模块加载、注册卡片、创建控制设备，到HAL层的音频通路配置文件初始化，以及设备调用底层的音频路由和设备启用。主要涉及snd_ctl_elem系列函数和audio_route_init过程。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

1.kernel 部分control控制codec寄存器流程

module_platform_driver(msm8x16_asoc_machine_driver)-------------------------kernel/sound/soc/msm/msm8x16.c

->msm8x16_asoc_machine_probe

->snd_soc_register_card(card)

->snd_soc_instantiate_card(card)

->snd_card_create()

->snd_ctl_create(card)

->snd_ctl_dev_register()

->snd_register_device(SNDRV_DEVICE_TYPE_CONTROL, card, -1,&snd_ctl_f_ops, card, name)--------------------------kernel/sound/core/control.c

->snd_ctl_ioctl()

->snd_ctl_elem_info_user(ctl, argp)

->snd_ctl_elem_read_user(card, argp)

->snd_ctl_elem_write_user(ctl, argp)

->snd_ctl_elem_write(card, file, control)

->snd_ctl_find_id(card, &control->id)

->kctl->put(kctl, control)

snd_kcontrol_newmsm_snd_controls[]---------------------------------------kernel/sound/soc/msm/msm8x16.c

->snd_soc_add_codec_controls(codec,msm_snd_controls,ARRAY_SIZE(msm_snd_controls))

->snd_soc_add_controls()

->snd_ctl_add()

->list_add_tail(&kcontrol->list, &card->controls)

2.hal层调用音频通路配置文件mixer_paths_mtp.xml初始化流程

qcom/audio/hal/msm8916/platform.c:40:#defineMIXER_XML_PATH_MTP "/system/etc/mixer_paths_mtp.xml"

static void query_platform(const char *snd_card_name,

528 char*mixer_xml_path)

529 {

530 if (!strncmp(snd_card_name, "msm8x16-snd-card-mtp",

531 sizeof("msm8x16-snd-card-mtp"))) {

532 strlcpy(mixer_xml_path, MIXER_XML_PATH_MTP,

533 sizeof(MIXER_XML_PATH_MTP));

………

999 }

adev->audio_route= audio_route_init(snd_card_num,mixer_xml_path);

system/media/audio_route/include/audio_route/audio_route.h:25:structaudio_route *audio_route_init(unsigned int card, const char *xml_path);

system/media/audio_route/audio_route.c:721:structaudio_route *audio_route_init(unsignedint card, const char *xml_path)

3.hal层设备调用底层流程

start_output_stream(structstream_out *out)

->select_devices(adev,out->usecase)

->enable_snd_device(adev,out_snd_device)

->audio_route_apply_and_update_path(adev->audio_route,device_name)

->audio_route_update_path(ar,name, false /*reverse*/)

->mixer_ctl_set_value(ms->ctl, 0, ms->new_value[0])

->mixer_ctl_set_array(ms->ctl, ms->new_value, ms->num_values)

->ioctl(ctl->mixer->fd, SNDRV_CTL_IOCTL_ELEM_WRITE, &ev)