2 files changed, 129 insertions, 39 deletions

diff --git a/drivers/usb/gadget/function/f_midi.c b/drivers/usb/gadget/function/f_midi.c
index 79dc611..fb1fe96d 100644
--- a/drivers/usb/gadget/function/f_midi.c
+++ b/drivers/usb/gadget/function/f_midi.c
@@ -23,6 +23,7 @@
 #include <linux/module.h>
 #include <linux/slab.h>
 #include <linux/device.h>
+#include <linux/kfifo.h>
 
 #include <sound/core.h>
 #include <sound/initval.h>
@@ -88,6 +89,9 @@ struct f_midi {
 	int index;
 	char *id;
 	unsigned int buflen, qlen;
+	/* This fifo is used as a buffer ring for pre-allocated IN usb_requests */
+	DECLARE_KFIFO_PTR(in_req_fifo, struct usb_request *);
+	unsigned int in_last_port;
 };
 
 static inline struct f_midi *func_to_midi(struct usb_function *f)
@@ -95,7 +99,7 @@ static inline struct f_midi *func_to_midi(struct usb_function *f)
 	return container_of(f, struct f_midi, func);
 }
 
-static void f_midi_transmit(struct f_midi *midi, struct usb_request *req);
+static void f_midi_transmit(struct f_midi *midi);
 
 DECLARE_UAC_AC_HEADER_DESCRIPTOR(1);
 DECLARE_USB_MIDI_OUT_JACK_DESCRIPTOR(1);
@@ -253,7 +257,8 @@ f_midi_complete(struct usb_ep *ep, struct usb_request *req)
 		} else if (ep == midi->in_ep) {
 			/* Our transmit completed. See if there's more to go.
 			 * f_midi_transmit eats req, don't queue it again. */
-			f_midi_transmit(midi, req);
+			req->length = 0;
+			f_midi_transmit(midi);
 			return;
 		}
 		break;
@@ -264,10 +269,12 @@ f_midi_complete(struct usb_ep *ep, struct usb_request *req)
 	case -ESHUTDOWN:	/* disconnect from host */
 		VDBG(cdev, "%s gone (%d), %d/%d\n", ep->name, status,
 				req->actual, req->length);
-		if (ep == midi->out_ep)
+		if (ep == midi->out_ep) {
 			f_midi_handle_out_data(ep, req);
-
-		free_ep_req(ep, req);
+			/* We don't need to free IN requests because it's handled
+			 * by the midi->in_req_fifo. */
+			free_ep_req(ep, req);
+		}
 		return;
 
 	case -EOVERFLOW:	/* buffer overrun on read means that
@@ -334,6 +341,20 @@ static int f_midi_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
 	if (err)
 		return err;
 
+	/* pre-allocate write usb requests to use on f_midi_transmit. */
+	while (kfifo_avail(&midi->in_req_fifo)) {
+		struct usb_request *req =
+			midi_alloc_ep_req(midi->in_ep, midi->buflen);
+
+		if (req == NULL)
+			return -ENOMEM;
+
+		req->length = 0;
+		req->complete = f_midi_complete;
+
+		kfifo_put(&midi->in_req_fifo, req);
+	}
+
 	/* allocate a bunch of read buffers and queue them all at once. */
 	for (i = 0; i < midi->qlen && err == 0; i++) {
 		struct usb_request *req =
@@ -358,6 +379,7 @@ static void f_midi_disable(struct usb_function *f)
 {
 	struct f_midi *midi = func_to_midi(f);
 	struct usb_composite_dev *cdev = f->config->cdev;
+	struct usb_request *req = NULL;
 
 	DBG(cdev, "disable\n");
 
@@ -367,6 +389,10 @@ static void f_midi_disable(struct usb_function *f)
 	 */
 	usb_ep_disable(midi->in_ep);
 	usb_ep_disable(midi->out_ep);
+
+	/* release IN requests */
+	while (kfifo_get(&midi->in_req_fifo, &req))
+		free_ep_req(midi->in_ep, req);
 }
 
 static int f_midi_snd_free(struct snd_device *device)
@@ -488,57 +514,113 @@ static void f_midi_transmit_byte(struct usb_request *req,
 	}
 }
 
-static void f_midi_transmit(struct f_midi *midi, struct usb_request *req)
+static void f_midi_drop_out_substreams(struct f_midi *midi)
 {
-	struct usb_ep *ep = midi->in_ep;
-	int i;
-
-	if (!ep)
-		return;
-
-	if (!req)
-		req = midi_alloc_ep_req(ep, midi->buflen);
-
-	if (!req) {
-		ERROR(midi, "%s: alloc_ep_request failed\n", __func__);
-		return;
-	}
-	req->length = 0;
-	req->complete = f_midi_complete;
+	unsigned int i;
 
 	for (i = 0; i < MAX_PORTS; i++) {
 		struct gmidi_in_port *port = midi->in_port[i];
 		struct snd_rawmidi_substream *substream = midi->in_substream[i];
 
-		if (!port || !port->active || !substream)
+		if (!port)
+			break;
+
+		if (!port->active || !substream)
 			continue;
 
-		while (req->length + 3 < midi->buflen) {
-			uint8_t b;
-			if (snd_rawmidi_transmit(substream, &b, 1) != 1) {
-				port->active = 0;
+		snd_rawmidi_drop_output(substream);
+	}
+}
+
+static void f_midi_transmit(struct f_midi *midi)
+{
+	struct usb_ep *ep = midi->in_ep;
+	bool active;
+
+	/* We only care about USB requests if IN endpoint is enabled */
+	if (!ep || !ep->enabled)
+		goto drop_out;
+
+	do {
+		struct usb_request *req = NULL;
+		unsigned int len, i;
+
+		active = false;
+
+		/* We peek the request in order to reuse it if it fails
+		 * to enqueue on its endpoint */
+		len = kfifo_peek(&midi->in_req_fifo, &req);
+		if (len != 1) {
+			ERROR(midi, "%s: Couldn't get usb request\n", __func__);
+			goto drop_out;
+		}
+
+		/* If buffer overrun, then we ignore this transmission.
+		 * IMPORTANT: This will cause the user-space rawmidi device to block until a) usb
+		 * requests have been completed or b) snd_rawmidi_write() times out. */
+		if (req->length > 0)
+			return;
+
+		for (i = midi->in_last_port; i < MAX_PORTS; i++) {
+			struct gmidi_in_port *port = midi->in_port[i];
+			struct snd_rawmidi_substream *substream = midi->in_substream[i];
+
+			if (!port) {
+				/* Reset counter when we reach the last available port */
+				midi->in_last_port = 0;
+				break;
+			}
+
+			if (!port->active || !substream)
+				continue;
+
+			while (req->length + 3 < midi->buflen) {
+				uint8_t b;
+
+				if (snd_rawmidi_transmit(substream, &b, 1) != 1) {
+					port->active = 0;
+					break;
+				}
+				f_midi_transmit_byte(req, port, b);
+			}
+
+			active = !!port->active;
+			/* Check if last port is still active, which means that
+			 * there is still data on that substream but this current
+			 * request run out of space. */
+			if (active) {
+				midi->in_last_port = i;
+				/* There is no need to re-iterate though midi ports. */
 				break;
 			}
-			f_midi_transmit_byte(req, port, b);
 		}
-	}
 
-	if (req->length > 0 && ep->enabled) {
-		int err;
+		if (req->length > 0) {
+			int err;
 
-		err = usb_ep_queue(ep, req, GFP_ATOMIC);
-		if (err < 0)
-			ERROR(midi, "%s queue req: %d\n",
-			      midi->in_ep->name, err);
-	} else {
-		free_ep_req(ep, req);
-	}
+			err = usb_ep_queue(ep, req, GFP_ATOMIC);
+			if (err < 0) {
+				ERROR(midi, "%s failed to queue req: %d\n",
+				      midi->in_ep->name, err);
+				req->length = 0; /* Re-use request next time. */
+			} else {
+				/* Upon success, put request at the back of the queue. */
+				kfifo_skip(&midi->in_req_fifo);
+				kfifo_put(&midi->in_req_fifo, req);
+			}
+		}
+	} while (active);
+
+	return;
+
+drop_out:
+	f_midi_drop_out_substreams(midi);
 }
 
 static void f_midi_in_tasklet(unsigned long data)
 {
 	struct f_midi *midi = (struct f_midi *) data;
-	f_midi_transmit(midi, NULL);
+	f_midi_transmit(midi);
 }
 
 static int f_midi_in_open(struct snd_rawmidi_substream *substream)
@@ -664,6 +746,7 @@ static int f_midi_register_card(struct f_midi *midi)
 		goto fail;
 	}
 	midi->rmidi = rmidi;
+	midi->in_last_port = 0;
 	strcpy(rmidi->name, card->shortname);
 	rmidi->info_flags = SNDRV_RAWMIDI_INFO_OUTPUT |
 			    SNDRV_RAWMIDI_INFO_INPUT |
@@ -1053,6 +1136,7 @@ static void f_midi_free(struct usb_function *f)
 	mutex_lock(&opts->lock);
 	for (i = opts->in_ports - 1; i >= 0; --i)
 		kfree(midi->in_port[i]);
+	kfifo_free(&midi->in_req_fifo);
 	kfree(midi);
 	--opts->refcnt;
 	mutex_unlock(&opts->lock);
@@ -1126,6 +1210,12 @@ static struct usb_function *f_midi_alloc(struct usb_function_instance *fi)
 	midi->index = opts->index;
 	midi->buflen = opts->buflen;
 	midi->qlen = opts->qlen;
+	midi->in_last_port = 0;
+
+	status = kfifo_alloc(&midi->in_req_fifo, midi->qlen, GFP_KERNEL);
+	if (status)
+		goto setup_fail;
+
 	++opts->refcnt;
 	mutex_unlock(&opts->lock);
 
diff --git a/drivers/usb/gadget/legacy/gmidi.c b/drivers/usb/gadget/legacy/gmidi.c
index e27aad5..fc2ac15 100644
--- a/drivers/usb/gadget/legacy/gmidi.c
+++ b/drivers/usb/gadget/legacy/gmidi.c
@@ -53,7 +53,7 @@ MODULE_PARM_DESC(buflen, "MIDI buffer length");
 
 static unsigned int qlen = 32;
 module_param(qlen, uint, S_IRUGO);
-MODULE_PARM_DESC(qlen, "USB read request queue length");
+MODULE_PARM_DESC(qlen, "USB read and write request queue length");
 
 static unsigned int in_ports = 1;
 module_param(in_ports, uint, S_IRUGO);