[PATCH 3/3] selftests: ALSA: pcmtest: Test pausing a capture stream

[HyeongJun An]

The driver supports pause, but no test uses it.

Add a capture test that pauses the stream halfway for half a second.
The core does not read the hardware pointer while the stream is
paused, so a driver that keeps running shows up only at the release,
as a jump of the pointer. Check that the jump is under a tenth of a
second, and that the data carries on from where it stopped.

Assisted-by: Claude:claude-opus-5-5
Signed-off-by: HyeongJun An <sammiee5311@xxxxxxxxx>
---
 .../selftests/alsa/test-pcmtest-driver.c      | 49 +++++++++++++++++++
 1 file changed, 49 insertions(+)

diff --git a/tools/testing/selftests/alsa/test-pcmtest-driver.c b/tools/testing/selftests/alsa/test-pcmtest-driver.c
index 380364ee7924..b796a5613c6f 100644
--- a/tools/testing/selftests/alsa/test-pcmtest-driver.c
+++ b/tools/testing/selftests/alsa/test-pcmtest-driver.c
@@ -7,6 +7,7 @@
  */
 #include <errno.h>
 #include <string.h>
+#include <unistd.h>
 #include <alsa/asoundlib.h>
 #include "kselftest_harness.h"
 
@@ -362,6 +363,54 @@ TEST_F(pcmtest, reset_ioctl) {
 	snd_pcm_close(handle);
 }
 
+/*
+ * Here we pause a capture stream halfway. The core does not read the hardware pointer while
+ * the stream is paused, so a driver that keeps running only shows up after the release, as a
+ * jump of the pointer. The data must also continue where it stopped, so the whole buffer still
+ * matches the patterns.
+ */
+TEST_F(pcmtest, capture_pause) {
+	snd_pcm_t *handle;
+	snd_pcm_sframes_t read_res, paused_avail, avail, frames, half;
+	unsigned char *samples;
+	struct pcmtest_test_params *params = &self->params;
+
+	samples = calloc(params->sec_buf_len * params->time, 1);
+	ASSERT_NE(samples, NULL);
+
+	snd_pcm_sw_params_alloca(&self->swparams);
+	snd_pcm_hw_params_alloca(&self->hwparams);
+	ASSERT_EQ(setup_handle(&handle, self->swparams, self->hwparams, params,
+			       self->card, SND_PCM_STREAM_CAPTURE), 0);
+
+	frames = params->rate * params->time;
+	half = frames / 2;
+	read_res = snd_pcm_readi(handle, samples, half);
+	ASSERT_EQ(read_res, half);
+
+	ASSERT_EQ(snd_pcm_pause(handle, 1), 0);
+	ASSERT_EQ(snd_pcm_state(handle), SND_PCM_STATE_PAUSED);
+	paused_avail = snd_pcm_avail(handle);
+	ASSERT_GE(paused_avail, 0);
+	usleep(500000);
+
+	/*
+	 * At 8000 Hz the pause is 4000 frames long. Allow a tenth of a second (800 frames) for
+	 * the release.
+	 */
+	ASSERT_EQ(snd_pcm_pause(handle, 0), 0);
+	avail = snd_pcm_avail(handle);
+	ASSERT_GE(avail, 0);
+	ASSERT_LT(avail - paused_avail, (snd_pcm_sframes_t)params->rate / 10);
+	read_res = snd_pcm_readi(handle, samples + snd_pcm_frames_to_bytes(handle, half),
+				 frames - half);
+	ASSERT_EQ(read_res, frames - half);
+	snd_pcm_close(handle);
+
+	ASSERT_EQ(find_capture_mismatch(samples, params), -1);
+	free(samples);
+}
+
 /*
  * Here we check that an error from each PCM callback reaches user space. The driver returns
  * the error while the matching 'inject_*_err' parameter is set, and works again once it is
-- 
2.43.0