Hello,
I am puzzled by an observation that runs against my common sense. The pmic-alsa-mixer.c provides 6 (six) snd_kcontrol_new_t controls with their callback functions, name and other members, then registers themusing snd_ctl_add(...). However, amixer shows only 5 (five), and all with different names. What is the process of generating these names if not from the kernel structures?
By looking through the mixer related code in alsa-utils and alsa-libs, I see that somehow the library loads the mixer controls and possibly retrieves all the information provided by them, including their names. Either some piece of code shortens the names defined in the driver, or it maps them to some generic controls. Any suggestions?
The system I am working on uses a Freescale imx27 in conjunction with an MC13783 power management IC, also responsible for audio (it provides a voice codec and a stereo dac). The kernel used is a 2.6.19.2 as part of ltib from Freescale. amixer tells me:
mx27# amixer Simple mixer control 'Master',0 Capabilities: pvolume pvolume-joined cvolume Playback channels: Mono Capture channels: Mono Limits: Playback 0 - 100 Capture 0 - 100 Mono: Playback 0 [0%] Capture 0 [0%] Simple mixer control 'Master Balance',0 Capabilities: pvolume pvolume-joined Playback channels: Mono Limits: Playback 0 - 100 Mono: Playback 50 [50%] Simple mixer control 'Master Input',0 Capabilities: cvolume Capture channels: Mono Limits: Capture 0 - 7 Mono: Capture 1 [14%] Simple mixer control 'Master Monoconfig',0 Capabilities: pvolume pvolume-joined Playback channels: Mono Limits: Playback 0 - 3 Mono: Playback 0 [0%] Simple mixer control 'Master Output',0 Capabilities: pvolume pvolume-joined Playback channels: Mono Limits: Playback 0 - 15 Mono: Playback 12 [80%]
snd_kcontrol_new_t pmic_control_pb_vol __devinitdata = { .iface = SNDRV_CTL_ELEM_IFACE_MIXER, .name = "Master Playback Volume", .index = 0x00, .info = pmic_pb_volume_info, .get = pmic_pb_volume_get, .put = pmic_pb_volume_put, .private_value = 0xffab1, };
snd_kcontrol_new_t pmic_control_pb_bal __devinitdata = { .iface = SNDRV_CTL_ELEM_IFACE_MIXER, .name = "Master Balance Playback Volume", .index = 0x00, .info = pmic_pb_balance_info, .get = pmic_pb_balance_get, .put = pmic_pb_balance_put, .private_value = 0xffab2, }; snd_kcontrol_new_t pmic_control_pb_mono __devinitdata = { .iface = SNDRV_CTL_ELEM_IFACE_MIXER, .name = "Master Monoconfig Playback Volume", .index = 0x00, .info = pmic_pb_monoconfig_info, .get = pmic_pb_monoconfig_get, .put = pmic_pb_monoconfig_put, .private_value = 0xffab2, }; snd_kcontrol_new_t pmic_control_op_sw __devinitdata = { .iface = SNDRV_CTL_ELEM_IFACE_MIXER, .name = "Master Output Playback Volume", .index = 0x00, .info = pmic_mixer_output_info, .get = pmic_mixer_output_get, .put = pmic_mixer_output_put, .private_value = 0xffab4, };
snd_kcontrol_new_t pmic_control_cap_vol __devinitdata = { .iface = SNDRV_CTL_ELEM_IFACE_MIXER, .name = "Master Capture Volume", .index = 0x00, .info = pmic_cap_volume_info, .get = pmic_cap_volume_get, .put = pmic_cap_volume_put, .private_value = 0xffab5, }; snd_kcontrol_new_t pmic_control_ip_sw __devinitdata = { .iface = SNDRV_CTL_ELEM_IFACE_MIXER, .name = "Master Input Capture Volume", .index = 0x00, .info = pmic_cap_input_info, .get = pmic_cap_input_get, .put = pmic_cap_input_put, .private_value = 0xffab5, };
int mxc_alsa_create_ctl(snd_card_t * card, void *p_value) { int err = 0;
if ((err = snd_ctl_add(card, snd_ctl_new1(&pmic_control_op_sw, p_value))) < 0) return err;
if ((err = snd_ctl_add(card, snd_ctl_new1(&pmic_control_pb_vol, p_value))) < 0) return err; if ((err = snd_ctl_add(card, snd_ctl_new1(&pmic_control_pb_mono, p_value))) < 0) return err; if ((err = snd_ctl_add(card, snd_ctl_new1(&pmic_control_pb_bal, p_value))) < 0) return err; if ((err = snd_ctl_add(card, snd_ctl_new1(&pmic_control_cap_vol, p_value))) < 0) return err; if ((err = snd_ctl_add(card, snd_ctl_new1(&pmic_control_ip_sw, p_value))) < 0) return err;
return 0; }
Cheers, peter