drivers: add sound card driver support

Add driver core boilerplate for sound support in barebox. Using the
provided API in <sound.h>, consumers can play beeps for a fixed duration
of time.

Playing beeps is not blocking and new beeps can be enqueued while one
is already playing. They will be played in succession by a poller, which
will also turn off the sound card when the beep tune is over.

API is also available for blocking until all beeps are played and for
cancelling an underway beep tune.

The API could be later extended for arbitrary PCM audio, should the
need arise.

Signed-off-by: Ahmad Fatoum <ahmad@a3f.at>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

2 files changed, 49 insertions, 0 deletions

diff --git a/include/poller.h b/include/poller.h
index 886557252b..db773265b2 100644
--- a/include/poller.h
+++ b/include/poller.h
@@ -34,6 +34,10 @@ int poller_async_unregister(struct poller_async *pa);
 int poller_call_async(struct poller_async *pa, uint64_t delay_ns,
 		void (*fn)(void *), void *ctx);
 int poller_async_cancel(struct poller_async *pa);
+static inline bool poller_async_active(struct poller_async *pa)
+{
+	return pa->active;
+}
 
 #ifdef CONFIG_POLLER
 void poller_call(void);
diff --git a/include/sound.h b/include/sound.h
new file mode 100644
index 0000000000..f5124aebbd
--- /dev/null
+++ b/include/sound.h
@@ -0,0 +1,45 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* SPDX-FileCopyrightText: © 2021 Ahmad Fatoum */
+
+#ifndef __SOUND_H_
+#define __SOUND_H_
+
+#include <linux/list.h>
+#include <poller.h>
+
+#define BELL_DEFAULT_FREQUENCY	-1
+
+struct sound_card {
+	const char *name;
+	int bell_frequency;
+	int (*beep)(struct sound_card *, unsigned freq, unsigned us);
+
+	/* private */
+	struct list_head list;
+	struct list_head tune;
+	struct poller_async poller;
+};
+
+int sound_card_register(struct sound_card *card);
+int sound_card_beep_wait(struct sound_card *card, unsigned timeout_us);
+int sound_card_beep(struct sound_card *card, int freq, unsigned int us);
+int sound_card_beep_cancel(struct sound_card *card);
+
+struct sound_card *sound_card_get_default(void);
+
+static inline int beep(int freq, unsigned us)
+{
+	return sound_card_beep(sound_card_get_default(), freq, us);
+}
+
+static inline int beep_wait(unsigned timeout_us)
+{
+	return sound_card_beep_wait(sound_card_get_default(), timeout_us);
+}
+
+static inline int beep_cancel(void)
+{
+	return sound_card_beep_cancel(sound_card_get_default());
+}
+
+#endif