ALSA: line6: Add hwdep interface to access the POD control messages

We must do it this way, because e.g. POD X3 won't play any sound unless
the host listens on the bulk EP, so we cannot export it only via libusb.

The driver currently doesn't use the bulk EP messages in other way,
in future it could e.g. sense/modify volume(s).

Signed-off-by: Andrej Krutak <dev@andree.sk>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

1 files changed, 148 insertions, 4 deletions

diff --git a/sound/usb/line6/driver.c b/sound/usb/line6/driver.c
index 8a71d45ce945..f9224ec141c8 100644
--- a/sound/usb/line6/driver.c
+++ b/sound/usb/line6/driver.c
@@ -17,6 +17,7 @@
 
 #include <sound/core.h>
 #include <sound/initval.h>
+#include <sound/hwdep.h>
 
 #include "capture.h"
 #include "driver.h"
@@ -303,7 +304,7 @@ static void line6_data_received(struct urb *urb)
 		for (;;) {
 			done =
 				line6_midibuf_read(mb, line6->buffer_message,
-						LINE6_MESSAGE_MAXLEN);
+						LINE6_MIDI_MESSAGE_MAXLEN);
 
 			if (done == 0)
 				break;
@@ -315,8 +316,11 @@ static void line6_data_received(struct urb *urb)
 				line6->process_message(line6);
 		}
 	} else {
+		line6->buffer_message = urb->transfer_buffer;
+		line6->message_length = urb->actual_length;
 		if (line6->process_message)
 			line6->process_message(line6);
+		line6->buffer_message = NULL;
 	}
 
 	line6_start_listen(line6);
@@ -473,14 +477,17 @@ static void line6_destruct(struct snd_card *card)
 	struct usb_line6 *line6 = card->private_data;
 	struct usb_device *usbdev = line6->usbdev;
 
-	/* free buffer memory first: */
-	if (line6->properties->capabilities & LINE6_CAP_CONTROL_MIDI)
+	/* Free buffer memory first. We cannot depend on the existence of private
+	 * data from the (podhd) module, it may be gone already during this call
+	 */
+	if (line6->buffer_message)
 		kfree(line6->buffer_message);
 
 	kfree(line6->buffer_listen);
 
 	/* then free URBs: */
 	usb_free_urb(line6->urb_listen);
+	line6->urb_listen = NULL;
 
 	/* decrement reference counters: */
 	usb_put_dev(usbdev);
@@ -522,6 +529,138 @@ static void line6_get_interval(struct usb_line6 *line6)
 	}
 }
 
+
+/* Enable buffering of incoming messages, flush the buffer */
+static int line6_hwdep_open(struct snd_hwdep *hw, struct file *file)
+{
+	struct usb_line6 *line6 = hw->private_data;
+
+	/* NOTE: hwdep layer provides atomicity here */
+
+	line6->messages.active = 1;
+
+	return 0;
+}
+
+/* Stop buffering */
+static int line6_hwdep_release(struct snd_hwdep *hw, struct file *file)
+{
+	struct usb_line6 *line6 = hw->private_data;
+
+	line6->messages.active = 0;
+
+	return 0;
+}
+
+/* Read from circular buffer, return to user */
+static long
+line6_hwdep_read(struct snd_hwdep *hwdep, char __user *buf, long count,
+					loff_t *offset)
+{
+	struct usb_line6 *line6 = hwdep->private_data;
+	long rv = 0;
+	unsigned int out_count;
+
+	if (mutex_lock_interruptible(&line6->messages.read_lock))
+		return -ERESTARTSYS;
+
+	while (kfifo_len(&line6->messages.fifo) == 0) {
+		mutex_unlock(&line6->messages.read_lock);
+
+		rv = wait_event_interruptible(
+			line6->messages.wait_queue,
+			kfifo_len(&line6->messages.fifo) != 0);
+		if (rv < 0)
+			return rv;
+
+		if (mutex_lock_interruptible(&line6->messages.read_lock))
+			return -ERESTARTSYS;
+	}
+
+	if (kfifo_peek_len(&line6->messages.fifo) > count) {
+		/* Buffer too small; allow re-read of the current item... */
+		rv = -EINVAL;
+	} else {
+		rv = kfifo_to_user(&line6->messages.fifo, buf, count, &out_count);
+		if (rv == 0)
+			rv = out_count;
+	}
+
+	mutex_unlock(&line6->messages.read_lock);
+	return rv;
+}
+
+/* Write directly (no buffering) to device by user*/
+static long
+line6_hwdep_write(struct snd_hwdep *hwdep, const char __user *data, long count,
+					loff_t *offset)
+{
+	struct usb_line6 *line6 = hwdep->private_data;
+	int rv;
+	char *data_copy;
+
+	if (count > line6->max_packet_size * LINE6_RAW_MESSAGES_MAXCOUNT) {
+		/* This is an arbitrary limit - still better than nothing... */
+		return -EINVAL;
+	}
+
+	data_copy = memdup_user(data, count);
+	if (IS_ERR(ERR_PTR))
+		return -ENOMEM;
+
+	rv = line6_send_raw_message(line6, data_copy, count);
+
+	kfree(data_copy);
+	return rv;
+}
+
+static const struct snd_hwdep_ops hwdep_ops = {
+	.open    = line6_hwdep_open,
+	.release = line6_hwdep_release,
+	.read    = line6_hwdep_read,
+	.write   = line6_hwdep_write,
+};
+
+/* Insert into circular buffer */
+static void line6_hwdep_push_message(struct usb_line6 *line6)
+{
+	if (!line6->messages.active)
+		return;
+
+	if (kfifo_avail(&line6->messages.fifo) >= line6->message_length) {
+		/* No race condition here, there's only one writer */
+		kfifo_in(&line6->messages.fifo,
+			line6->buffer_message, line6->message_length);
+	} /* else TODO: signal overflow */
+
+	wake_up_interruptible(&line6->messages.wait_queue);
+}
+
+static int line6_hwdep_init(struct usb_line6 *line6)
+{
+	int err;
+	struct snd_hwdep *hwdep;
+
+	/* TODO: usb_driver_claim_interface(); */
+	line6->process_message = line6_hwdep_push_message;
+	line6->messages.active = 0;
+	init_waitqueue_head(&line6->messages.wait_queue);
+	mutex_init(&line6->messages.read_lock);
+	INIT_KFIFO(line6->messages.fifo);
+
+	err = snd_hwdep_new(line6->card, "config", 0, &hwdep);
+	if (err < 0)
+		goto end;
+	strcpy(hwdep->name, "config");
+	hwdep->iface = SNDRV_HWDEP_IFACE_LINE6;
+	hwdep->ops = hwdep_ops;
+	hwdep->private_data = line6;
+	hwdep->exclusive = true;
+
+end:
+	return err;
+}
+
 static int line6_init_cap_control(struct usb_line6 *line6)
 {
 	int ret;
@@ -536,9 +675,13 @@ static int line6_init_cap_control(struct usb_line6 *line6)
 		return -ENOMEM;
 
 	if (line6->properties->capabilities & LINE6_CAP_CONTROL_MIDI) {
-		line6->buffer_message = kmalloc(LINE6_MESSAGE_MAXLEN, GFP_KERNEL);
+		line6->buffer_message = kmalloc(LINE6_MIDI_MESSAGE_MAXLEN, GFP_KERNEL);
 		if (!line6->buffer_message)
 			return -ENOMEM;
+	} else {
+		ret = line6_hwdep_init(line6);
+		if (ret < 0)
+			return ret;
 	}
 
 	ret = line6_start_listen(line6);
@@ -716,3 +859,4 @@ EXPORT_SYMBOL_GPL(line6_resume);
 MODULE_AUTHOR(DRIVER_AUTHOR);
 MODULE_DESCRIPTION(DRIVER_DESC);
 MODULE_LICENSE("GPL");
+