pisound improvements:

* Added a writable sysfs object to enable scripts / user space software
to blink MIDI activity LEDs for variable duration.
* Improved hw_param constraints setting.
* Added compatibility with S16_LE sample format.
* Exposed some simple placeholder volume controls, so the card appears
in volumealsa widget.

Signed-off-by: Giedrius Trainavicius <giedrius@blokas.io>

sound/soc/bcm/pisound.c

@@ -36,6 +36,7 @@
 #include <sound/jack.h>
 #include <sound/rawmidi.h>
 #include <sound/asequencer.h>
+#include <sound/control.h>
 
 static int pisnd_spi_init(struct device *dev);
 static void pisnd_spi_uninit(void);
@@ -214,6 +215,9 @@ static char g_serial_num[11];
 static char g_id[25];
 static char g_version[5];
 
+static uint8_t g_ledFlashDuration;
+static bool    g_ledFlashDurationChanged;
+
 DEFINE_KFIFO(spi_fifo_in,  uint8_t, FIFO_SIZE);
 DEFINE_KFIFO(spi_fifo_out, uint8_t, FIFO_SIZE);
 
@@ -396,8 +400,13 @@ static void pisnd_work_handler(struct work_struct *work)
 			val = 0;
 			tx = 0;
 
-			if (kfifo_get(&spi_fifo_out, &val))
+			if (g_ledFlashDurationChanged) {
+				tx = 0xf000 | g_ledFlashDuration;
+				g_ledFlashDuration = 0;
+				g_ledFlashDurationChanged = false;
+			} else if (kfifo_get(&spi_fifo_out, &val)) {
 				tx = 0x0f00 | val;
+			}
 
 			rx = spi_transfer16(tx);
 
@@ -410,6 +419,7 @@ static void pisnd_work_handler(struct work_struct *work)
 		} while (rx != 0
 			|| !kfifo_is_empty(&spi_fifo_out)
 			|| pisnd_spi_has_more()
+			|| g_ledFlashDurationChanged
 			);
 
 		if (!kfifo_is_empty(&spi_fifo_in) && g_recvCallback)
@@ -569,7 +579,7 @@ static int pisnd_spi_init(struct device *dev)
 	}
 
 	/* Flash the LEDs. */
-	spi_transfer16(0xf000);
+	spi_transfer16(0xf008);
 
 	ret = pisnd_spi_gpio_irq_init(dev);
 	if (ret < 0) {
@@ -610,6 +620,14 @@ static void pisnd_spi_uninit(void)
 	pisnd_spi_gpio_uninit();
 }
 
+static void pisnd_spi_flash_leds(uint8_t duration)
+{
+	g_ledFlashDuration = duration;
+	g_ledFlashDurationChanged = true;
+	printd("schedule from spi_flash_leds\n");
+	pisnd_schedule_process(TASK_PROCESS);
+}
+
 static void pisnd_spi_send(uint8_t val)
 {
 	kfifo_put(&spi_fifo_out, val);
@@ -658,6 +676,83 @@ static const struct of_device_id pisound_of_match[] = {
 	{},
 };
 
+enum {
+	SWITCH = 0,
+	VOLUME = 1,
+};
+
+static int pisnd_ctl_info(struct snd_kcontrol *kcontrol,
+	struct snd_ctl_elem_info *uinfo)
+{
+	if (kcontrol->private_value == SWITCH) {
+		uinfo->type = SNDRV_CTL_ELEM_TYPE_BOOLEAN;
+		uinfo->count = 1;
+		uinfo->value.integer.min = 0;
+		uinfo->value.integer.max = 1;
+		return 0;
+	} else if (kcontrol->private_value == VOLUME) {
+		uinfo->type = SNDRV_CTL_ELEM_TYPE_INTEGER;
+		uinfo->count = 1;
+		uinfo->value.integer.min = 0;
+		uinfo->value.integer.max = 100;
+		return 0;
+	}
+	return -EINVAL;
+}
+
+static int pisnd_ctl_get(struct snd_kcontrol *kcontrol,
+	struct snd_ctl_elem_value *ucontrol)
+{
+	if (kcontrol->private_value == SWITCH) {
+		ucontrol->value.integer.value[0] = 1;
+		return 0;
+	} else if (kcontrol->private_value == VOLUME) {
+		ucontrol->value.integer.value[0] = 100;
+		return 0;
+	}
+
+	return -EINVAL;
+}
+
+static struct snd_kcontrol_new pisnd_ctl[] = {
+	{
+		.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
+		.name = "PCM Playback Switch",
+		.index = 0,
+		.private_value = SWITCH,
+		.access = SNDRV_CTL_ELEM_ACCESS_READ,
+		.info = pisnd_ctl_info,
+		.get = pisnd_ctl_get,
+	},
+	{
+		.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
+		.name = "PCM Playback Volume",
+		.index = 0,
+		.private_value = VOLUME,
+		.access = SNDRV_CTL_ELEM_ACCESS_READ,
+		.info = pisnd_ctl_info,
+		.get = pisnd_ctl_get,
+	},
+};
+
+static int pisnd_ctl_init(struct snd_card *card)
+{
+	int err, i;
+
+	for (i = 0; i < ARRAY_SIZE(pisnd_ctl); ++i) {
+		err = snd_ctl_add(card, snd_ctl_new1(&pisnd_ctl[i], NULL));
+		if (err < 0)
+			return err;
+	}
+
+	return 0;
+}
+
+static int pisnd_ctl_uninit(void)
+{
+	return 0;
+}
+
 static struct gpio_desc *osr0, *osr1, *osr2;
 static struct gpio_desc *reset;
 static struct gpio_desc *button;
@@ -667,6 +762,14 @@ static int pisnd_hw_params(
 	struct snd_pcm_hw_params *params
 	)
 {
+	struct snd_soc_pcm_runtime *rtd = substream->private_data;
+	struct snd_soc_dai *cpu_dai = rtd->cpu_dai;
+
+	/* pisound runs on fixed 32 clock counts per channel,
+	 * as generated by the master ADC.
+	 */
+	snd_soc_dai_set_bclk_ratio(cpu_dai, 32*2);
+
 	printd("rate   = %d\n", params_rate(params));
 	printd("ch     = %d\n", params_channels(params));
 	printd("bits   = %u\n",
@@ -711,16 +814,6 @@ static struct snd_pcm_hw_constraint_list constraints_rates = {
 	.mask = 0,
 };
 
-static unsigned int sample_bits[] = {
-	24, 32
-};
-
-static struct snd_pcm_hw_constraint_list constraints_sample_bits = {
-	.count = ARRAY_SIZE(sample_bits),
-	.list = sample_bits,
-	.mask = 0,
-};
-
 static int pisnd_startup(struct snd_pcm_substream *substream)
 {
 	int err = snd_pcm_hw_constraint_list(
@@ -733,11 +826,21 @@ static int pisnd_startup(struct snd_pcm_substream *substream)
 	if (err < 0)
 		return err;
 
-	err = snd_pcm_hw_constraint_list(
+	err = snd_pcm_hw_constraint_single(
 		substream->runtime,
-		0,
-		SNDRV_PCM_HW_PARAM_SAMPLE_BITS,
-		&constraints_sample_bits
+		SNDRV_PCM_HW_PARAM_CHANNELS,
+		2
+		);
+
+	if (err < 0)
+		return err;
+
+	err = snd_pcm_hw_constraint_mask64(
+		substream->runtime,
+		SNDRV_PCM_HW_PARAM_FORMAT,
+		SNDRV_PCM_FMTBIT_S16_LE |
+		SNDRV_PCM_FMTBIT_S24_LE |
+		SNDRV_PCM_FMTBIT_S32_LE
 		);
 
 	if (err < 0)
@@ -771,14 +874,23 @@ static int pisnd_card_probe(struct snd_soc_card *card)
 {
 	int err = pisnd_midi_init(card->snd_card);
 
-	if (err < 0)
+	if (err < 0) {
 		printe("pisnd_midi_init failed: %d\n", err);
+		return err;
+	}
 
-	return err;
+	err = pisnd_ctl_init(card->snd_card);
+	if (err < 0) {
+		printe("pisnd_ctl_init failed: %d\n", err);
+		return err;
+	}
+
+	return 0;
 }
 
 static int pisnd_card_remove(struct snd_soc_card *card)
 {
+	pisnd_ctl_uninit();
 	pisnd_midi_uninit();
 	return 0;
 }
@@ -870,17 +982,38 @@ static ssize_t pisnd_version_show(
 	return sprintf(buf, "%s\n", pisnd_spi_get_version());
 }
 
+static ssize_t pisnd_led_store(
+	struct kobject *kobj,
+	struct kobj_attribute *attr,
+	const char *buf,
+	size_t length
+	)
+{
+	uint32_t timeout;
+	int err;
+
+	err = kstrtou32(buf, 10, &timeout);
+
+	if (err == 0 && timeout <= 255)
+		pisnd_spi_flash_leds(timeout);
+
+	return length;
+}
+
 static struct kobj_attribute pisnd_serial_attribute =
-	__ATTR(serial, 0644, pisnd_serial_show, NULL);
+	__ATTR(serial, 0444, pisnd_serial_show, NULL);
 static struct kobj_attribute pisnd_id_attribute =
-	__ATTR(id, 0644, pisnd_id_show, NULL);
+	__ATTR(id, 0444, pisnd_id_show, NULL);
 static struct kobj_attribute pisnd_version_attribute =
-	__ATTR(version, 0644, pisnd_version_show, NULL);
+	__ATTR(version, 0444, pisnd_version_show, NULL);
+static struct kobj_attribute pisnd_led_attribute =
+	__ATTR(led, 0644, NULL, pisnd_led_store);
 
 static struct attribute *attrs[] = {
 	&pisnd_serial_attribute.attr,
 	&pisnd_id_attribute.attr,
 	&pisnd_version_attribute.attr,
+	&pisnd_led_attribute.attr,
 	NULL
 };