Changes to show the different transfer methods

test/pcm.c

@@ -22,7 +22,6 @@ double freq = 440;				 /* sinus wave frequency in Hz */
 
 snd_pcm_sframes_t buffer_size;
 snd_pcm_sframes_t period_size;
-signed short *samples;
 snd_output_t *output = NULL;
 
 static void generate_sine(signed short *samples, int count, double *_phase)
@@ -145,6 +144,155 @@ static int set_swparams(snd_pcm_t *handle, snd_pcm_sw_params_t *swparams)
 	return 0;
 }
 
+/*
+ *   Underrun and suspend recovery
+ */
+ 
+static int xrun_recovery(snd_pcm_t *handle, int err)
+{
+	if (err = -EPIPE) {	/* underrun */
+		err = snd_pcm_prepare(handle);
+		if (err < 0)
+			printf("Can't recovery from underrun, prepare failed: %s\n", snd_strerror(err));
+		return 0;
+	} else if (err = -ESTRPIPE) {
+		while ((err = snd_pcm_resume(handle)) == -EAGAIN)
+			sleep(1);	/* wait until suspend flag is released */
+		if (err < 0) {
+			err = snd_pcm_prepare(handle);
+			if (err < 0)
+				printf("Can't recovery from suspend, prepare failed: %s\n", snd_strerror(err));
+		}
+		return 0;
+	}
+	return err;
+}
+
+/*
+ *   Transfer method - write only
+ */
+
+static int write_loop(snd_pcm_t *handle, signed short *samples)
+{
+	int ufds_count;
+	struct pollfd *ufds;
+	double phase = 0;
+	signed short *ptr;
+	int err, count, cptr;
+
+	while (1) {
+		generate_sine(ptr = samples, cptr = period_size, &phase);
+		while (cptr > 0) {
+			err = snd_pcm_writei(handle, ptr, cptr);
+			if (err == -EAGAIN)
+				continue;
+			if (err < 0) {
+				if (xrun_recovery(handle, err) < 0) {
+					printf("Write error: %s\n", snd_strerror(err));
+					exit(EXIT_FAILURE);
+				}
+				break;	/* skip one period */
+			}
+			ptr += err * channels;
+			cptr -= err;
+		}
+	}
+}
+ 
+/*
+ *   Transfer method - write and wait for room in buffer using poll
+ */
+
+static int wait_for_poll(struct pollfd *ufds, int count)
+{
+	int i;
+	unsigned int events;
+
+	while (1) {
+		poll(ufds, count, -1);
+		for (i = 0; i < count; i++) {
+			events = ufds[i].revents;
+			if (events & POLLERR) {
+				printf("Poll - POLLERR detected\n");
+				return -EIO;
+			}
+			if (events & POLLOUT)
+				return 0;
+		}
+	}
+}
+
+static int write_and_poll_loop(snd_pcm_t *handle, signed short *samples)
+{
+	int ufds_count;
+	struct pollfd *ufds;
+	double phase = 0;
+	signed short *ptr;
+	int err, count, cptr;
+
+	count = snd_pcm_poll_descriptors_count (handle);
+	if (count <= 0) {
+		printf("Invalid poll descriptors count\n");
+		return count;
+	}
+
+	ufds = malloc(sizeof(struct pollfd) * count);
+	if (ufds == NULL) {
+		printf("No enough memory\n");
+		return err;;
+	}
+	if ((err = snd_pcm_poll_descriptors(handle, ufds, count)) < 0) {
+		printf("Unable to obtain poll descriptors for playback: %s\n", snd_strerror(err));
+		return err;
+	}
+
+	while (1) {
+		err = wait_for_poll(ufds, count);
+		if (err < 0) {
+			printf("Wait for poll failed\n");
+			return err;
+		}
+
+		generate_sine(ptr = samples, cptr = period_size, &phase);
+		while (cptr > 0) {
+			err = snd_pcm_writei(handle, ptr, cptr);
+			if (err < 0) {
+				if (xrun_recovery(handle, err) < 0) {
+					printf("Write error: %s\n", snd_strerror(err));
+					exit(EXIT_FAILURE);
+				}
+				break;	/* skip one period */
+			}
+			ptr += err * channels;
+			cptr -= err;
+			if (cptr == 0)
+				break;
+			/* it is possible, that initial buffer cannot store */
+			/* all data from last period, so wait awhile */
+			err = wait_for_poll(ufds, count);
+			if (err < 0) {
+				printf("Wait for poll failed\n");
+				return err;
+			}
+		}
+	}
+}
+
+/*
+ *
+ */
+
+struct transfer_method {
+	const char *name;
+	int (*transfer_loop)(snd_pcm_t *handle, signed short *samples);
+};
+
+static struct transfer_method transfer_methods[] = {
+	{ "write", write_loop },
+	{ "write_and_poll", write_and_poll_loop },
+	{ NULL, NULL }
+};
+
 static void help(void)
 {
 	int k;
@@ -157,6 +305,8 @@ Usage: latency [OPTION]... [FILE]...
 -f,--frequency  sine wave frequency in Hz
 -b,--buffer     ring buffer size in samples
 -p,--period     period size in us
+-m,--method     tranfer method
+
 ");
         printf("Recognized sample formats are:");
         for (k = 0; k < SND_PCM_FORMAT_LAST; ++(unsigned long) k) {
@@ -165,6 +315,10 @@ Usage: latency [OPTION]... [FILE]...
                         printf(" %s", s);
         }
         printf("\n");
+        printf("Recognized tranfer methods are:");
+        for (k = 0; transfer_methods[k].name; k++)
+        	printf(" %s", transfer_methods[k].name);
+	printf("\n");
 }
 
 int main(int argc, char *argv[])
@@ -178,18 +332,17 @@ int main(int argc, char *argv[])
 		{"frequency", 1, NULL, 'f'},
 		{"buffer", 1, NULL, 'b'},
 		{"period", 1, NULL, 'p'},
+		{"method", 1, NULL, 'm'},
 		{NULL, 0, NULL, 0},
 	};
 	snd_pcm_t *handle;
 	char *buffer;
-	int err, morehelp, i, count;
+	int err, morehelp;
 	snd_pcm_hw_params_t *hwparams;
 	snd_pcm_sw_params_t *swparams;
-	struct pollfd *ufds;
-	unsigned int events;
 	double phase;
-	signed short *ptr;
+	int method = 0;
-	int cptr;
+	signed short *samples;
 
 	snd_pcm_hw_params_alloca(&hwparams);
 	snd_pcm_sw_params_alloca(&swparams);
@@ -197,7 +350,7 @@ int main(int argc, char *argv[])
 	morehelp = 0;
 	while (1) {
 		int c;
-		if ((c = getopt_long(argc, argv, "hD:r:c:f:b:p:", long_option, NULL)) < 0)
+		if ((c = getopt_long(argc, argv, "hD:r:c:f:b:p:m:", long_option, NULL)) < 0)
 			break;
 		switch (c) {
 		case 'h':
@@ -231,6 +384,13 @@ int main(int argc, char *argv[])
 			period_time = period_time < 1000 ? 1000 : period_time;
 			period_time = period_time > 1000000 ? 1000000 : period_time;
 			break;
+		case 'm':
+			for (method = 0; transfer_methods[method].name; method++)
+				if (!strcasecmp(transfer_methods[method].name, optarg))
+					break;
+			if (transfer_methods[method].name == NULL)
+				method = 0;
+			break;
 		}
 	}
 
@@ -248,6 +408,7 @@ int main(int argc, char *argv[])
 	printf("Playback device is %s\n", device);
 	printf("Stream parameters are %iHz, %s, %i channels\n", rate, snd_pcm_format_name(format), channels);
 	printf("Sine wave rate is %.4fHz\n", freq);
+	printf("Using transfer method: %s\n", transfer_methods[method].name);
 
 	if ((err = snd_pcm_open(&handle, device, SND_PCM_STREAM_PLAYBACK, SND_PCM_NONBLOCK)) < 0) {
 		printf("Playback open error: %s\n", snd_strerror(err));
@@ -263,59 +424,15 @@ int main(int argc, char *argv[])
 		exit(EXIT_FAILURE);
 	}
 
-	count = snd_pcm_poll_descriptors_count (handle);
-	if (count <= 0) {
-		printf("Invalid poll descriptors count\n");
-		exit(EXIT_FAILURE);
-	}
-	ufds = malloc(sizeof(struct pollfd) * count);
-	if (ufds == NULL) {
-		printf("No enough memory\n");
-		exit(EXIT_FAILURE);
-	}
-	if ((err = snd_pcm_poll_descriptors(handle, ufds, count)) < 0) {
-		printf("Unable to obtain poll descriptors for playback: %s\n", snd_strerror(err));
-		exit(EXIT_FAILURE);
-	}
-	
 	samples = malloc((period_size * channels * snd_pcm_format_width(format)) / 8);
 	if (samples == NULL) {
 		printf("No enough memory\n");
 		exit(EXIT_FAILURE);
 	}
 
-	phase = 0;
+	err = transfer_methods[method].transfer_loop(handle, samples);
-
+	if (err < 0)
-	while (1) {
+		printf("Transfer failed: %s\n", snd_strerror(err));
-		poll(ufds, count, -1);
-		for (i = 0; i < count; i++) {
-			events = ufds[i].revents;
-			if (events & POLLOUT)
-				goto __write;
-		}
-		continue;
-
-	      __write:
-		generate_sine(ptr = samples, cptr = period_size, &phase);
-		while (cptr > 0) {
-			err = snd_pcm_writei(handle, ptr, cptr);
-			if (err < 0) {
-				printf("Write error: %s\n", snd_strerror(err));
-				exit(EXIT_FAILURE);
-			}
-			ptr += err * channels;
-			cptr -= err;
-			while (1) {
-				poll(ufds, count, -1);
-				for (i = 0; i < count; i++) {
-					events = ufds[i].revents;
-					if (events & POLLOUT)
-						goto __write1;
-				}
-			}
-		      __write1:
-		}
-	}
 
 	snd_pcm_close(handle);
 	return 0;