commit b02dadd38071fc5f6fec5241c805077e7a5b818d
from: Omar Polo <op@omarpolo.com>
date: Sat May 13 15:09:34 2023 UTC

cache audio_nfds()

ALSA' snd_pcm_poll_descriptors_count() can fail with -EPIPE after
an underrun (e.g. after a pause), so we can't call it directly like
this.  It's also a bit sloppy to always call audio_nfds(), so instead
save the (initial) value returned and pass it to the various
functions.

Issue reported and fix tested by phoebos (ben [at] bvnf [dot] space),
thank you!

commit - 8b3efdb322551aaf432334c16a23f52789c22989
commit + b02dadd38071fc5f6fec5241c805077e7a5b818d
blob - 9127045e119cbe11c5ceedf4292c911ad6371228
blob + b6bba1c01bc22266594c48a8df59d27e7d75f905
--- amused.h
+++ amused.h
@@ -160,10 +160,10 @@ void		main_seek(struct player_seek *);
 /* audio_*.c */
 int		audio_open(void (*)(void *, int));
 int		audio_setup(unsigned int, unsigned int, unsigned int,
-		    struct pollfd *);
+		    struct pollfd *, int);
 int		audio_nfds(void);
-int		audio_pollfd(struct pollfd *, int);
-int		audio_revents(struct pollfd *);
+int		audio_pollfd(struct pollfd *, int, int);
+int		audio_revents(struct pollfd *, int);
 size_t		audio_write(const void *, size_t);
 int		audio_flush(void);
 int		audio_stop(void);
blob - 07f43795676ea21645ad6ae56597c54673a035e1
blob + 656fb1fd2fba1ba957d7f2e32a75e526b31502fb
--- audio_alsa.c
+++ audio_alsa.c
@@ -46,7 +46,7 @@ audio_open(void (*cb)(void *, int))
 
 int
 audio_setup(unsigned int bits, unsigned int rate, unsigned int channels,
-    struct pollfd *pfds)
+    struct pollfd *pfds, int nfds)
 {
 	int			 err;
 	snd_pcm_format_t	 fmt;
@@ -93,19 +93,18 @@ audio_nfds(void)
 }
 
 int
-audio_pollfd(struct pollfd *pfds, int events)
+audio_pollfd(struct pollfd *pfds, int nfds, int events)
 {
-	return snd_pcm_poll_descriptors(pcm, pfds, audio_nfds());
+	return snd_pcm_poll_descriptors(pcm, pfds, nfds);
 }
 
 int
-audio_revents(struct pollfd *pfds)
+audio_revents(struct pollfd *pfds, int nfds)
 {
 	int			 err;
 	unsigned short		 revents;
 
-	err = snd_pcm_poll_descriptors_revents(pcm, pfds, audio_nfds(),
-	    &revents);
+	err = snd_pcm_poll_descriptors_revents(pcm, pfds, nfds, &revents);
 	if (err < 0) {
 		log_warnx("snd revents failure: %s", snd_strerror(err));
 		return 0;
blob - 3a44d164a81a7d7317f6284e0b8c84aad10e3e30
blob + 0661a8964490d8814fcdbcc523c7df108198a4e1
--- audio_sndio.c
+++ audio_sndio.c
@@ -41,9 +41,9 @@ audio_open(void (*onmove_cb)(void *, int))
 
 int
 audio_setup(unsigned int bits, unsigned int rate, unsigned int channels,
-    struct pollfd *pfds)
+    struct pollfd *pfds, int nfds)
 {
-	int		 nfds, fpct;
+	int		 fpct;
 
 	fpct = (rate * 5) / 100;
 
@@ -67,7 +67,7 @@ audio_setup(unsigned int bits, unsigned int rate, unsi
 	par.pchan = channels;
 	if (!sio_setpar(hdl, &par)) {
 		if (errno == EAGAIN) {
-			nfds = sio_pollfd(hdl, pfds, POLLOUT);
+			sio_pollfd(hdl, pfds, POLLOUT);
 			if (poll(pfds, nfds, INFTIM) == -1)
 				fatal("poll");
 			goto again;
@@ -104,13 +104,13 @@ audio_nfds(void)
 }
 
 int
-audio_pollfd(struct pollfd *pfds, int events)
+audio_pollfd(struct pollfd *pfds, int nfds, int events)
 {
 	return sio_pollfd(hdl, pfds, events);
 }
 
 int
-audio_revents(struct pollfd *pfds)
+audio_revents(struct pollfd *pfds, int nfds)
 {
 	return sio_revents(hdl, pfds);
 }
blob - 0ed93412e48712f7bbcc9d065b04ecdb891ba734
blob + 8201dc2ee66cb298413f0d27ea16550637bdd069
--- player.c
+++ player.c
@@ -34,6 +34,7 @@
 #include "xmalloc.h"
 
 struct pollfd		*player_pfds;
+int			 player_nfds;
 static struct imsgbuf	*ibuf;
 
 static int nextfd = -1;
@@ -56,7 +57,7 @@ player_setup(unsigned int bits, unsigned int rate, uns
 	    bits, rate, channels);
 
 	current_rate = rate;
-	return audio_setup(bits, rate, channels, player_pfds + 1);
+	return audio_setup(bits, rate, channels, player_pfds + 1, player_nfds);
 }
 
 void
@@ -253,12 +254,12 @@ int
 play(const void *buf, size_t len, int64_t *s)
 {
 	size_t w;
-	int nfds, revents, r, wait;
+	int revents, r, wait;
 
 	*s = -1;
 	while (len != 0) {
-		nfds = audio_pollfd(player_pfds + 1, POLLOUT);
-		r = poll(player_pfds, nfds + 1, INFTIM);
+		audio_pollfd(player_pfds + 1, player_nfds, POLLOUT);
+		r = poll(player_pfds, player_nfds + 1, INFTIM);
 		if (r == -1)
 			fatal("poll");
 
@@ -268,7 +269,7 @@ play(const void *buf, size_t len, int64_t *s)
 			return 0;
 		}
 
-		revents = audio_revents(player_pfds + 1);
+		revents = audio_revents(player_pfds + 1, player_nfds);
 		if (revents & POLLHUP) {
 			if (errno == EAGAIN)
 				continue;
@@ -307,8 +308,12 @@ player(int debug, int verbose)
 	if (audio_open(player_onmove) == -1)
 		fatal("audio_open");
 
+	if ((player_nfds = audio_nfds()) <= 0)
+		fatal("audio_nfds: invalid number of file descriptors: %d",
+		    player_nfds);
+
 	/* allocate one extra for imsg */
-	player_pfds = calloc(audio_nfds() + 1, sizeof(*player_pfds));
+	player_pfds = calloc(player_nfds + 1, sizeof(*player_pfds));
 	if (player_pfds == NULL)
 		fatal("calloc");