Re: Adding kqueue to /dev/dsp

[Vladimir Kondratyev]

On 6/4/25 20:01, Goran Mekić wrote:

Hello,

I already talked to christos@ and he's OK with me adding the support for kqueue to /dev/dsp, but I never saw any docs on how to implement it in the kernel. Could somebody advise on how to add kqueue support to existing device? I mean, if you could point out the simple device code with kqueue support, I would be glad to follow the logic there and learn, for start. Thank you!

Regards,
meka

Hi Goran,

See attached patch. It enables kqueue support for psm(4)

--
WBR
Vladimir Kondratyev

From 2d4efd265bfeaea8e44c34ee796b69d99d3b12c5 Mon Sep 17 00:00:00 2001
From: Vladimir Kondratyev <w...@freebsd.org>
Date: Thu, 15 May 2025 07:53:59 +0300
Subject: [PATCH] psm(4): Add kqueue support

---
 sys/dev/atkbdc/psm.c | 45 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)

diff --git a/sys/dev/atkbdc/psm.c b/sys/dev/atkbdc/psm.c
index fbd9eb61fee..b429777a9d0 100644
--- a/sys/dev/atkbdc/psm.c
+++ b/sys/dev/atkbdc/psm.c
@@ -614,6 +614,7 @@ static d_read_t		psmread;
 static d_write_t	psmwrite;
 static d_ioctl_t	psmioctl;
 static d_poll_t		psmpoll;
+static d_kqfilter_t	psmkqfilter;
 
 static int	psmopen(struct psm_softc *);
 static int	psmclose(struct psm_softc *);
@@ -766,6 +767,7 @@ static struct cdevsw psm_cdevsw = {
 	.d_write =	psmwrite,
 	.d_ioctl =	psmioctl,
 	.d_poll =	psmpoll,
+	.d_kqfilter =	psmkqfilter,
 	.d_name =	PSM_DRIVER_NAME,
 };
 
@@ -1962,6 +1964,7 @@ psmattach(device_t dev)
 	sc->state = PSM_VALID;
 	callout_init(&sc->callout, 0);
 	callout_init(&sc->softcallout, 0);
+	knlist_init_mtx(&sc->rsel.si_note, &Giant);
 
 	/* Setup our interrupt handler */
 	rid = KBDC_RID_AUX;
@@ -2073,6 +2076,8 @@ psmdetach(device_t dev)
 	destroy_dev(sc->cdev);
 	destroy_dev(sc->bdev);
 
+	knlist_clear(&sc->rsel.si_note, 1);
+	knlist_destroy(&sc->rsel.si_note);
 	callout_drain(&sc->callout);
 	callout_drain(&sc->softcallout);
 
@@ -5229,6 +5234,7 @@ psmsoftintr(void *arg)
 		wakeup(sc);
 	}
 	selwakeuppri(&sc->rsel, PZERO);
+	KNOTE_LOCKED(&sc->rsel.si_note, 0);
 	if (sc->async != NULL) {
 		pgsigio(&sc->async, SIGIO, 0);
 	}
@@ -5266,6 +5272,45 @@ psmpoll(struct cdev *dev, int events, struct thread *td)
 	return (revents);
 }
 
+static void
+psmfilter_detach(struct knote *kn)
+{
+	struct psm_softc *sc = kn->kn_hook;
+
+	knlist_remove(&sc->rsel.si_note, kn, 0);
+}
+
+static int
+psmfilter(struct knote *kn, long hint)
+{
+	struct psm_softc *sc = kn->kn_hook;
+
+	GIANT_REQUIRED;
+
+	return (sc->queue.count != 0 ? 1 : 0);
+}
+
+static const struct filterops psmfiltops = {
+	.f_isfd = 1,
+	.f_detach = psmfilter_detach,
+	.f_event = psmfilter,
+};
+
+static int
+psmkqfilter(struct cdev *dev, struct knote *kn)
+{
+	struct psm_softc *sc = dev->si_drv1;
+
+	if (kn->kn_filter != EVFILT_READ)
+		return(EOPNOTSUPP);
+
+	kn->kn_fop = &psmfiltops;
+	kn->kn_hook = sc;
+	knlist_add(&sc->rsel.si_note, kn, 1);
+
+	return (0);
+}
+
 /* vendor/model specific routines */
 
 static int mouse_id_proc1(KBDC kbdc, int res, int scale, int *status)
-- 
2.49.0