From 6dcd6ba9b263d4c9414f431ec3c90dc70616aeb2 Mon Sep 17 00:00:00 2001
From: "Samuel J. Greear" <sjg@thesjg.com>
Date: Tue, 15 Jun 2010 16:13:45 +0000
Subject: [PATCH] kernel - Add kqueue read support to memio devices

 memio devices: mem, kmem, null, random, urandom, zero, io
---
 sys/kern/kern_memio.c   | 45 ++++++++++++++++++++++++++++++++++++++++-
 sys/kern/kern_nrandom.c | 10 +++++++++
 sys/sys/random.h        |  2 ++
 3 files changed, 56 insertions(+), 1 deletion(-)

diff --git a/sys/kern/kern_memio.c b/sys/kern/kern_memio.c
index 47e12fc8c8..f50a7a762c 100644
--- a/sys/kern/kern_memio.c
+++ b/sys/kern/kern_memio.c
@@ -75,16 +75,18 @@ static	d_write_t	mmwrite;
 static	d_ioctl_t	mmioctl;
 static	d_mmap_t	memmmap;
 static	d_poll_t	mmpoll;
+static	d_kqfilter_t	mmkqfilter;
 
 #define CDEV_MAJOR 2
 static struct dev_ops mem_ops = {
-	{ "mem", CDEV_MAJOR, D_MEM | D_MPSAFE_READ | D_MPSAFE_WRITE },
+	{ "mem", CDEV_MAJOR, D_MEM | D_MPSAFE_READ | D_MPSAFE_WRITE | D_KQFILTER },
 	.d_open =	mmopen,
 	.d_close =	mmclose,
 	.d_read =	mmread,
 	.d_write =	mmwrite,
 	.d_ioctl =	mmioctl,
 	.d_poll =	mmpoll,
+	.d_kqfilter =	mmkqfilter,
 	.d_mmap =	memmmap,
 };
 
@@ -546,6 +548,47 @@ mmpoll(struct dev_poll_args *ap)
 	return (0);
 }
 
+static int
+mm_filter_read(struct knote *kn, long hint)
+{
+	return (1);
+}
+
+static void
+dummy_filter_detach(struct knote *kn) {}
+
+static struct filterops random_read_filtops =
+        { 1, NULL, dummy_filter_detach, random_filter_read };
+
+static struct filterops mm_read_filtops =
+        { 1, NULL, dummy_filter_detach, mm_filter_read };
+
+int
+mmkqfilter(struct dev_kqfilter_args *ap)
+{
+	struct knote *kn = ap->a_kn;
+	cdev_t dev = ap->a_head.a_dev;
+
+	ap->a_result = 0;
+	switch (kn->kn_filter) {
+	case EVFILT_READ:
+		switch (minor(dev)) {
+		case 3:
+			kn->kn_fop = &random_read_filtops;
+			break;
+		default:
+			kn->kn_fop = &mm_read_filtops;
+			break;
+		}
+		break;
+	default:
+		ap->a_result = 1;
+		return (0);
+	}
+
+	return (0);
+}
+
 int
 iszerodev(cdev_t dev)
 {
diff --git a/sys/kern/kern_nrandom.c b/sys/kern/kern_nrandom.c
index 60205a4359..5ad67d6035 100644
--- a/sys/kern/kern_nrandom.c
+++ b/sys/kern/kern_nrandom.c
@@ -128,6 +128,7 @@
 #include <sys/kernel.h>
 #include <sys/systm.h>
 #include <sys/poll.h>
+#include <sys/event.h>
 #include <sys/random.h>
 #include <sys/systimer.h>
 #include <sys/time.h>
@@ -521,6 +522,15 @@ random_poll(cdev_t dev, int events)
 	return (revents);
 }
 
+/*
+ * Kqueue filter (always succeeds)
+ */
+int
+random_filter_read(struct knote *kn, long hint)
+{
+	return (1);
+}
+
 /*
  * Heavy weight random number generator.  May return less then the
  * requested number of bytes.
diff --git a/sys/sys/random.h b/sys/sys/random.h
index c53817dc4e..f19d562dc6 100644
--- a/sys/sys/random.h
+++ b/sys/sys/random.h
@@ -95,7 +95,9 @@ u_int read_random_unlimited(void *buf, u_int size);
 u_int write_random(const char *buf, u_int nbytes);
 #endif
 struct thread;
+struct knote;
 int random_poll(cdev_t dev, int events);
+int random_filter_read(struct knote *kn, long hint);
 
 #endif /* _KERNEL */
 
-- 
2.41.0