1. 根目录:
2. sound
3. core
4. ctljack.c

/*
 * Helper functions for jack-detection kcontrols
 *
 * Copyright (c) 2011 Takashi Iwai <tiwai@suse.de>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the Free
 * Software Foundation; either version 2 of the License, or (at your option)
 * any later version.
 */

#include <linux/kernel.h>
#include <linux/export.h>
#include <sound/core.h>
#include <sound/control.h>

#define jack_detect_kctl_info	snd_ctl_boolean_mono_info

static int jack_detect_kctl_get(struct snd_kcontrol *kcontrol,
				struct snd_ctl_elem_value *ucontrol)
{
	ucontrol->value.integer.value[0] = kcontrol->private_value;
	return 0;
}

static struct snd_kcontrol_new jack_detect_kctl = {
	/* name is filled later */
	.iface = SNDRV_CTL_ELEM_IFACE_CARD,
	.access = SNDRV_CTL_ELEM_ACCESS_READ,
	.info = jack_detect_kctl_info,
	.get = jack_detect_kctl_get,
};

static int get_available_index(struct snd_card *card, const char *name)
{
	struct snd_ctl_elem_id sid;

	memset(&sid, 0, sizeof(sid));

	sid.index = 0;
	sid.iface = SNDRV_CTL_ELEM_IFACE_CARD;
	strlcpy(sid.name, name, sizeof(sid.name));

	while (snd_ctl_find_id(card, &sid)) {
		sid.index++;
		/* reset numid; otherwise snd_ctl_find_id() hits this again */
		sid.numid = 0;
	}

	return sid.index;
}

static void jack_kctl_name_gen(char *name, const char *src_name, int size)
{
	size_t count = strlen(src_name);
	bool need_cat = true;

	/* remove redundant " Jack" from src_name */
	if (count >= 5)
		need_cat = strncmp(&src_name[count - 5], " Jack", 5) ? true : false;

	snprintf(name, size, need_cat ? "%s Jack" : "%s", src_name);

}

struct snd_kcontrol *
snd_kctl_jack_new(const char *name, struct snd_card *card)
{
	struct snd_kcontrol *kctl;

	kctl = snd_ctl_new1(&jack_detect_kctl, NULL);
	if (!kctl)
		return NULL;

	jack_kctl_name_gen(kctl->id.name, name, sizeof(kctl->id.name));
	kctl->id.index = get_available_index(card, kctl->id.name);
	kctl->private_value = 0;
	return kctl;
}

void snd_kctl_jack_report(struct snd_card *card,
			  struct snd_kcontrol *kctl, bool status)
{
	if (kctl->private_value == status)
		return;
	kctl->private_value = status;
	snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_VALUE, &kctl->id);
}