sound: Implement dummy driver

Sponsored by:	The FreeBSD Foundation
MFC after:	2 days
Reviewed by:	dev_submerge.ch
Differential Revision:	https://reviews.freebsd.org/D45967

(cherry picked from commit c15c9315b2cb7601cc337f7d5a8e124f4b2d5861)

share/man/man4/Makefile

@@ -513,6 +513,7 @@ MAN=	aac.4 \
 	snd_cmi.4 \
 	snd_cs4281.4 \
 	snd_csa.4 \
+	snd_dummy.4 \
 	snd_emu10k1.4 \
 	snd_emu10kx.4 \
 	snd_envy24.4 \

share/man/man4/snd_dummy.4

@@ -0,0 +1,69 @@
+.\"-
+.\" SPDX-License-Identifier: BSD-2-Clause
+.\"
+.\" Copyright (c) 2024 The FreeBSD Foundation
+.\"
+.\" Portions of this software were developed by Christos Margiolis
+.\" <christos@FreeBSD.org> under sponsorship from the FreeBSD Foundation.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\"    notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\"    notice, this list of conditions and the following disclaimer in the
+.\"    documentation and/or other materials provided with the distribution.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+.\" SUCH DAMAGE.
+.\"
+.Dd July 15, 2024
+.Dt SND_DUMMY 4
+.Os
+.Sh NAME
+.Nm snd_dummy
+.Nd Dummy audio driver
+.Sh SYNOPSIS
+To load the driver at boot time, place the following line in
+.Xr loader.conf 5 :
+.Bd -literal -offset indent
+snd_dummy_load="YES"
+.Ed
+.Sh DESCRIPTION
+The
+.Nm
+driver implements a virtual testing device, meaning it does not correspond to a
+physical sound card.
+It is intended for testing, so that test programs do not need to rely on
+hardware being present in the machine in order to run.
+.Pp
+The driver attaches as a regular PCM device, with two channels (one playback
+and one recording), as well as a mixer.
+.Pp
+Playback works by discarding all input, and recording by returning silence
+(zeros).
+.Sh SEE ALSO
+.Xr sound 4 ,
+.Xr loader.conf 5 ,
+.Xr loader 8
+.Sh AUTHORS
+The
+.Nm
+driver was implemented by
+.An Christos Margiolis Aq Mt christos@FreeBSD.org
+under sponsorship from the
+.Fx
+Foundation.
+.Sh CAVEATS
+Because the driver automatically attaches once the module is loaded, it can
+only be attached once.

sys/dev/sound/dummy.c

@@ -0,0 +1,353 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2024 The FreeBSD Foundation
+ *
+ * This software was developed by Christos Margiolis <christos@FreeBSD.org>
+ * under sponsorship from the FreeBSD Foundation.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+
+#include <sys/param.h>
+#include <sys/systm.h>
+#include <sys/kernel.h>
+#include <sys/bus.h>
+
+#ifdef HAVE_KERNEL_OPTION_HEADERS
+#include "opt_snd.h"
+#endif
+
+#include <dev/sound/pcm/sound.h>
+#include <mixer_if.h>
+
+#define DUMMY_NPCHAN	1
+#define DUMMY_NRCHAN	1
+#define DUMMY_NCHAN	(DUMMY_NPCHAN + DUMMY_NRCHAN)
+
+struct dummy_chan {
+	struct dummy_softc *sc;
+	struct pcm_channel *chan;
+	struct snd_dbuf *buf;
+	struct pcmchan_caps *caps;
+	uint32_t ptr;
+	int dir;
+	int run;
+};
+
+struct dummy_softc {
+	struct snddev_info info;
+	device_t dev;
+	uint32_t cap_fmts[4];
+	struct pcmchan_caps caps;
+	int chnum;
+	struct dummy_chan chans[DUMMY_NCHAN];
+	struct callout callout;
+	struct mtx *lock;
+};
+
+static void
+dummy_chan_io(void *arg)
+{
+	struct dummy_softc *sc = arg;
+	struct dummy_chan *ch;
+	int i = 0;
+
+	snd_mtxlock(sc->lock);
+
+	for (i = 0; i < sc->chnum; i++) {
+		ch = &sc->chans[i];
+		if (!ch->run)
+			continue;
+		if (ch->dir == PCMDIR_PLAY)
+			ch->ptr += sndbuf_getblksz(ch->buf);
+		else
+			sndbuf_fillsilence(ch->buf);
+		snd_mtxunlock(sc->lock);
+		chn_intr(ch->chan);
+		snd_mtxlock(sc->lock);
+	}
+	callout_schedule(&sc->callout, 1);
+
+	snd_mtxunlock(sc->lock);
+}
+
+static int
+dummy_chan_free(kobj_t obj, void *data)
+{
+	struct dummy_chan *ch =data;
+	uint8_t *buf;
+
+	buf = sndbuf_getbuf(ch->buf);
+	if (buf != NULL)
+		free(buf, M_DEVBUF);
+
+	return (0);
+}
+
+static void *
+dummy_chan_init(kobj_t obj, void *devinfo, struct snd_dbuf *b,
+    struct pcm_channel *c, int dir)
+{
+	struct dummy_softc *sc;
+	struct dummy_chan *ch;
+	uint8_t *buf;
+	size_t bufsz;
+
+	sc = devinfo;
+
+	snd_mtxlock(sc->lock);
+
+	ch = &sc->chans[sc->chnum++];
+	ch->sc = sc;
+	ch->dir = dir;
+	ch->chan = c;
+	ch->buf = b;
+	ch->caps = &sc->caps;
+
+	snd_mtxunlock(sc->lock);
+
+	bufsz = pcm_getbuffersize(sc->dev, 2048, 2048, 65536);
+	buf = malloc(bufsz, M_DEVBUF, M_WAITOK | M_ZERO);
+	if (sndbuf_setup(ch->buf, buf, bufsz) != 0) {
+		dummy_chan_free(obj, ch);
+		return (NULL);
+	}
+
+	return (ch);
+}
+
+static int
+dummy_chan_setformat(kobj_t obj, void *data, uint32_t format)
+{
+	struct dummy_chan *ch = data;
+	int i;
+
+	for (i = 0; ch->caps->fmtlist[i]; i++)
+		if (format == ch->caps->fmtlist[i])
+			return (0);
+
+	return (EINVAL);
+}
+
+static uint32_t
+dummy_chan_setspeed(kobj_t obj, void *data, uint32_t speed)
+{
+	struct dummy_chan *ch = data;
+
+	RANGE(speed, ch->caps->minspeed, ch->caps->maxspeed);
+
+	return (speed);
+}
+
+static uint32_t
+dummy_chan_setblocksize(kobj_t obj, void *data, uint32_t blocksize)
+{
+	struct dummy_chan *ch = data;
+
+	return (sndbuf_getblksz(ch->buf));
+}
+
+static int
+dummy_chan_trigger(kobj_t obj, void *data, int go)
+{
+	struct dummy_chan *ch = data;
+	struct dummy_softc *sc = ch->sc;
+
+	snd_mtxlock(sc->lock);
+
+	switch (go) {
+	case PCMTRIG_START:
+		if (!callout_active(&sc->callout))
+			callout_reset(&sc->callout, 1, dummy_chan_io, sc);
+		ch->ptr = 0;
+		ch->run = 1;
+		break;
+	case PCMTRIG_STOP:
+	case PCMTRIG_ABORT:
+		ch->run = 0;
+		if (callout_active(&sc->callout))
+			callout_stop(&sc->callout);
+	default:
+		break;
+	}
+
+	snd_mtxunlock(sc->lock);
+
+	return (0);
+}
+
+static uint32_t
+dummy_chan_getptr(kobj_t obj, void *data)
+{
+	struct dummy_chan *ch = data;
+
+	return (ch->run ? ch->ptr : 0);
+}
+
+static struct pcmchan_caps *
+dummy_chan_getcaps(kobj_t obj, void *data)
+{
+	struct dummy_chan *ch = data;
+
+	return (ch->caps);
+}
+
+static kobj_method_t dummy_chan_methods[] = {
+	KOBJMETHOD(channel_init,	dummy_chan_init),
+	KOBJMETHOD(channel_free,	dummy_chan_free),
+	KOBJMETHOD(channel_setformat,	dummy_chan_setformat),
+	KOBJMETHOD(channel_setspeed,	dummy_chan_setspeed),
+	KOBJMETHOD(channel_setblocksize,dummy_chan_setblocksize),
+	KOBJMETHOD(channel_trigger,	dummy_chan_trigger),
+	KOBJMETHOD(channel_getptr,	dummy_chan_getptr),
+	KOBJMETHOD(channel_getcaps,	dummy_chan_getcaps),
+	KOBJMETHOD_END
+};
+
+CHANNEL_DECLARE(dummy_chan);
+
+static int
+dummy_mixer_init(struct snd_mixer *m)
+{
+	struct dummy_softc *sc;
+
+	sc = mix_getdevinfo(m);
+	if (sc == NULL)
+		return (-1);
+
+	pcm_setflags(sc->dev, pcm_getflags(sc->dev) | SD_F_SOFTPCMVOL);
+	mix_setdevs(m, SOUND_MASK_PCM | SOUND_MASK_VOLUME | SOUND_MASK_RECLEV);
+	mix_setrecdevs(m, SOUND_MASK_RECLEV);
+
+	return (0);
+}
+
+static int
+dummy_mixer_set(struct snd_mixer *m, unsigned dev, unsigned left, unsigned right)
+{
+	return (0);
+}
+
+static uint32_t
+dummy_mixer_setrecsrc(struct snd_mixer *m, uint32_t src)
+{
+	return (src == SOUND_MASK_RECLEV ? src : 0);
+}
+
+static kobj_method_t dummy_mixer_methods[] = {
+	KOBJMETHOD(mixer_init,		dummy_mixer_init),
+	KOBJMETHOD(mixer_set,		dummy_mixer_set),
+	KOBJMETHOD(mixer_setrecsrc,	dummy_mixer_setrecsrc),
+	KOBJMETHOD_END
+};
+
+MIXER_DECLARE(dummy_mixer);
+
+static void
+dummy_identify(driver_t *driver, device_t parent)
+{
+	if (device_find_child(parent, driver->name, -1) != NULL)
+		return;
+	if (BUS_ADD_CHILD(parent, 0, driver->name, -1) == NULL)
+		device_printf(parent, "add child failed\n");
+}
+
+static int
+dummy_probe(device_t dev)
+{
+	device_set_desc(dev, "Dummy Audio Device");
+
+	return (0);
+}
+
+static int
+dummy_attach(device_t dev)
+{
+	struct dummy_softc *sc;
+	char status[SND_STATUSLEN];
+	int i = 0;
+
+	sc = device_get_softc(dev);
+	sc->dev = dev;
+	sc->lock = snd_mtxcreate(device_get_nameunit(dev), "snd_dummy softc");
+
+	sc->cap_fmts[0] = SND_FORMAT(AFMT_S32_LE, 2, 0);
+	sc->cap_fmts[1] = SND_FORMAT(AFMT_S24_LE, 2, 0);
+	sc->cap_fmts[2] = SND_FORMAT(AFMT_S16_LE, 2, 0);
+	sc->cap_fmts[3] = 0;
+	sc->caps = (struct pcmchan_caps){
+		8000,		/* minspeed */
+		96000,		/* maxspeed */
+		sc->cap_fmts,	/* fmtlist */
+		0,		/* caps */
+	};
+
+	pcm_setflags(dev, pcm_getflags(dev) | SD_F_MPSAFE);
+	if (pcm_register(dev, sc, DUMMY_NPCHAN, DUMMY_NRCHAN))
+		return (ENXIO);
+	for (i = 0; i < DUMMY_NPCHAN; i++)
+		pcm_addchan(dev, PCMDIR_PLAY, &dummy_chan_class, sc);
+	for (i = 0; i < DUMMY_NRCHAN; i++)
+		pcm_addchan(dev, PCMDIR_REC, &dummy_chan_class, sc);
+
+	snprintf(status, SND_STATUSLEN, "on %s",
+	    device_get_nameunit(device_get_parent(dev)));
+	pcm_setstatus(dev, status);
+	mixer_init(dev, &dummy_mixer_class, sc);
+	callout_init(&sc->callout, 1);
+
+	return (0);
+}
+
+static int
+dummy_detach(device_t dev)
+{
+	struct dummy_softc *sc = device_get_softc(dev);
+	int err;
+
+	err = pcm_unregister(dev);
+	snd_mtxfree(sc->lock);
+
+	return (err);
+}
+
+static device_method_t dummy_methods[] = {
+	/* Device interface */
+	DEVMETHOD(device_identify,	dummy_identify),
+	DEVMETHOD(device_probe,		dummy_probe),
+	DEVMETHOD(device_attach,	dummy_attach),
+	DEVMETHOD(device_detach,	dummy_detach),
+	DEVMETHOD_END
+};
+
+static driver_t dummy_driver = {
+	"pcm",
+	dummy_methods,
+	sizeof(struct dummy_softc),
+};
+
+DRIVER_MODULE(snd_dummy, nexus, dummy_driver, 0, 0);
+MODULE_DEPEND(snd_dummy, sound, SOUND_MINVER, SOUND_PREFVER, SOUND_MAXVER);
+MODULE_VERSION(snd_dummy, 1);

sys/modules/sound/driver/Makefile

@@ -9,6 +9,7 @@ SUBDIR=		als4000 atiixp cs4281 ${_csa} emu10k1 emu10kx
 SUBDIR+=	envy24 envy24ht es137x fm801 hda hdspe ich
 SUBDIR+=	${_maestro3} neomagic solo spicds t4dwave via8233
 SUBDIR+=	via82c686 vibes driver uaudio
+SUBDIR+=	dummy
 
 .if ${MK_SOURCELESS_UCODE} != "no"
 _csa=		csa

sys/modules/sound/driver/dummy/Makefile

@@ -0,0 +1,7 @@
+.PATH: ${SRCTOP}/sys/dev/sound
+
+KMOD=	snd_dummy
+SRCS=	bus_if.h device_if.h
+SRCS+=	dummy.c
+
+.include <bsd.kmod.mk>