usb: gadget: hidg: register OUT INT endpoint for SET_REPORT

The hidg function driver currently handles its SET_REPORT calls via EP0.
This is the implicit behaviour when no OUT interrupt endpoint is
configured and generally works fine.

The problem is that due to EP0's role in the gadget framework, we cannot
hold back packets and control traffic flow to sync it to the char device,
and hence there's a high risk of loosing packets with this
implementation.

This patch adds an OUT interrupt endpoint to the interface and queues a
fix number of request to catch SET_REPORT events. According to the
specs, host drivers should always use the dedicated OUT endpoint when
present.

The char device's read implementation was rewritten to retrieve data
from the list of completed output requests.

Signed-off-by: Daniel Mack <zonque@gmail.com>
Cc: Felipe Balbi <balbi@ti.com>
Cc: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/gadget/f_hid.c

@@ -26,6 +26,12 @@ static struct class *hidg_class;
 /*-------------------------------------------------------------------------*/
 /*                            HID gadget struct                            */
 
+struct f_hidg_req_list {
+	struct usb_request	*req;
+	unsigned int		pos;
+	struct list_head 	list;
+};
+
 struct f_hidg {
 	/* configuration */
 	unsigned char			bInterfaceSubClass;
@@ -35,10 +41,10 @@ struct f_hidg {
 	unsigned short			report_length;
 
 	/* recv report */
-	char				*set_report_buff;
-	unsigned short			set_report_length;
+	struct list_head		completed_out_req;
 	spinlock_t			spinlock;
 	wait_queue_head_t		read_queue;
+	unsigned int			qlen;
 
 	/* send report */
 	struct mutex			lock;
@@ -49,7 +55,9 @@ struct f_hidg {
 	int				minor;
 	struct cdev			cdev;
 	struct usb_function		func;
+
 	struct usb_ep			*in_ep;
+	struct usb_ep			*out_ep;
 };
 
 static inline struct f_hidg *func_to_hidg(struct usb_function *f)
@@ -65,7 +73,7 @@ static struct usb_interface_descriptor hidg_interface_desc = {
 	.bDescriptorType	= USB_DT_INTERFACE,
 	/* .bInterfaceNumber	= DYNAMIC */
 	.bAlternateSetting	= 0,
-	.bNumEndpoints		= 1,
+	.bNumEndpoints		= 2,
 	.bInterfaceClass	= USB_CLASS_HID,
 	/* .bInterfaceSubClass	= DYNAMIC */
 	/* .bInterfaceProtocol	= DYNAMIC */
@@ -96,10 +104,23 @@ static struct usb_endpoint_descriptor hidg_hs_in_ep_desc = {
 				      */
 };
 
+static struct usb_endpoint_descriptor hidg_hs_out_ep_desc = {
+	.bLength		= USB_DT_ENDPOINT_SIZE,
+	.bDescriptorType	= USB_DT_ENDPOINT,
+	.bEndpointAddress	= USB_DIR_OUT,
+	.bmAttributes		= USB_ENDPOINT_XFER_INT,
+	/*.wMaxPacketSize	= DYNAMIC */
+	.bInterval		= 4, /* FIXME: Add this field in the
+				      * HID gadget configuration?
+				      * (struct hidg_func_descriptor)
+				      */
+};
+
 static struct usb_descriptor_header *hidg_hs_descriptors[] = {
 	(struct usb_descriptor_header *)&hidg_interface_desc,
 	(struct usb_descriptor_header *)&hidg_desc,
 	(struct usb_descriptor_header *)&hidg_hs_in_ep_desc,
+	(struct usb_descriptor_header *)&hidg_hs_out_ep_desc,
 	NULL,
 };
 
@@ -117,10 +138,23 @@ static struct usb_endpoint_descriptor hidg_fs_in_ep_desc = {
 				       */
 };
 
+static struct usb_endpoint_descriptor hidg_fs_out_ep_desc = {
+	.bLength		= USB_DT_ENDPOINT_SIZE,
+	.bDescriptorType	= USB_DT_ENDPOINT,
+	.bEndpointAddress	= USB_DIR_OUT,
+	.bmAttributes		= USB_ENDPOINT_XFER_INT,
+	/*.wMaxPacketSize	= DYNAMIC */
+	.bInterval		= 10, /* FIXME: Add this field in the
+				       * HID gadget configuration?
+				       * (struct hidg_func_descriptor)
+				       */
+};
+
 static struct usb_descriptor_header *hidg_fs_descriptors[] = {
 	(struct usb_descriptor_header *)&hidg_interface_desc,
 	(struct usb_descriptor_header *)&hidg_desc,
 	(struct usb_descriptor_header *)&hidg_fs_in_ep_desc,
+	(struct usb_descriptor_header *)&hidg_fs_out_ep_desc,
 	NULL,
 };
 
@@ -130,9 +164,11 @@ static struct usb_descriptor_header *hidg_fs_descriptors[] = {
 static ssize_t f_hidg_read(struct file *file, char __user *buffer,
 			size_t count, loff_t *ptr)
 {
-	struct f_hidg	*hidg     = file->private_data;
-	char		*tmp_buff = NULL;
-	unsigned long	flags;
+	struct f_hidg *hidg = file->private_data;
+	struct f_hidg_req_list *list;
+	struct usb_request *req;
+	unsigned long flags;
+	int ret;
 
 	if (!count)
 		return 0;
@@ -142,8 +178,9 @@ static ssize_t f_hidg_read(struct file *file, char __user *buffer,
 
 	spin_lock_irqsave(&hidg->spinlock, flags);
 
-#define READ_COND (hidg->set_report_buff != NULL)
+#define READ_COND (!list_empty(&hidg->completed_out_req))
 
+	/* wait for at least one buffer to complete */
 	while (!READ_COND) {
 		spin_unlock_irqrestore(&hidg->spinlock, flags);
 		if (file->f_flags & O_NONBLOCK)
@@ -155,19 +192,34 @@ static ssize_t f_hidg_read(struct file *file, char __user *buffer,
 		spin_lock_irqsave(&hidg->spinlock, flags);
 	}
 
-
-	count = min_t(unsigned, count, hidg->set_report_length);
-	tmp_buff = hidg->set_report_buff;
-	hidg->set_report_buff = NULL;
-
+	/* pick the first one */
+	list = list_first_entry(&hidg->completed_out_req,
+				struct f_hidg_req_list, list);
+	req = list->req;
+	count = min_t(unsigned int, count, req->actual - list->pos);
 	spin_unlock_irqrestore(&hidg->spinlock, flags);
 
-	if (tmp_buff != NULL) {
-		/* copy to user outside spinlock */
-		count -= copy_to_user(buffer, tmp_buff, count);
-		kfree(tmp_buff);
-	} else
-		count = -ENOMEM;
+	/* copy to user outside spinlock */
+	count -= copy_to_user(buffer, req->buf + list->pos, count);
+	list->pos += count;
+
+	/*
+	 * if this request is completely handled and transfered to
+	 * userspace, remove its entry from the list and requeue it
+	 * again. Otherwise, we will revisit it again upon the next
+	 * call, taking into account its current read position.
+	 */
+	if (list->pos == req->actual) {
+		spin_lock_irqsave(&hidg->spinlock, flags);
+		list_del(&list->list);
+		kfree(list);
+		spin_unlock_irqrestore(&hidg->spinlock, flags);
+
+		req->length = hidg->report_length;
+		ret = usb_ep_queue(hidg->out_ep, req, GFP_KERNEL);
+		if (ret < 0)
+			return ret;
+	}
 
 	return count;
 }
@@ -282,28 +334,37 @@ static int f_hidg_open(struct inode *inode, struct file *fd)
 /*-------------------------------------------------------------------------*/
 /*                                usb_function                             */
 
-static void hidg_set_report_complete(struct usb_ep *ep, struct usb_request *req)
+static struct usb_request *hidg_alloc_ep_req(struct usb_ep *ep, unsigned length)
 {
-	struct f_hidg *hidg = (struct f_hidg *)req->context;
-
-	if (req->status != 0 || req->buf == NULL || req->actual == 0) {
-		ERROR(hidg->func.config->cdev, "%s FAILED\n", __func__);
-		return;
+	struct usb_request *req;
+
+	req = usb_ep_alloc_request(ep, GFP_ATOMIC);
+	if (req) {
+		req->length = length;
+		req->buf = kmalloc(length, GFP_ATOMIC);
+		if (!req->buf) {
+			usb_ep_free_request(ep, req);
+			req = NULL;
+		}
 	}
+	return req;
+}
 
-	spin_lock(&hidg->spinlock);
-
-	hidg->set_report_buff = krealloc(hidg->set_report_buff,
-					 req->actual, GFP_ATOMIC);
+static void hidg_set_report_complete(struct usb_ep *ep, struct usb_request *req)
+{
+	struct f_hidg *hidg = (struct f_hidg *) req->context;
+	struct f_hidg_req_list *req_list;
+	unsigned long flags;
 
-	if (hidg->set_report_buff == NULL) {
-		spin_unlock(&hidg->spinlock);
+	req_list = kzalloc(sizeof(*req_list), GFP_ATOMIC);
+	if (!req_list)
 		return;
-	}
-	hidg->set_report_length = req->actual;
-	memcpy(hidg->set_report_buff, req->buf, req->actual);
 
-	spin_unlock(&hidg->spinlock);
+	req_list->req = req;
+
+	spin_lock_irqsave(&hidg->spinlock, flags);
+	list_add_tail(&req_list->list, &hidg->completed_out_req);
+	spin_unlock_irqrestore(&hidg->spinlock, flags);
 
 	wake_up(&hidg->read_queue);
 }
@@ -344,9 +405,7 @@ static int hidg_setup(struct usb_function *f,
 	case ((USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_INTERFACE) << 8
 		  | HID_REQ_SET_REPORT):
 		VDBG(cdev, "set_report | wLenght=%d\n", ctrl->wLength);
-		req->context  = hidg;
-		req->complete = hidg_set_report_complete;
-		goto respond;
+		goto stall;
 		break;
 
 	case ((USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_INTERFACE) << 8
@@ -403,16 +462,25 @@ respond:
 static void hidg_disable(struct usb_function *f)
 {
 	struct f_hidg *hidg = func_to_hidg(f);
+	struct f_hidg_req_list *list, *next;
 
 	usb_ep_disable(hidg->in_ep);
 	hidg->in_ep->driver_data = NULL;
+
+	usb_ep_disable(hidg->out_ep);
+	hidg->out_ep->driver_data = NULL;
+
+	list_for_each_entry_safe(list, next, &hidg->completed_out_req, list) {
+		list_del(&list->list);
+		kfree(list);
+	}
 }
 
 static int hidg_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
 {
 	struct usb_composite_dev		*cdev = f->config->cdev;
 	struct f_hidg				*hidg = func_to_hidg(f);
-	int status = 0;
+	int i, status = 0;
 
 	VDBG(cdev, "hidg_set_alt intf:%d alt:%d\n", intf, alt);
 
@@ -429,11 +497,55 @@ static int hidg_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
 		}
 		status = usb_ep_enable(hidg->in_ep);
 		if (status < 0) {
-			ERROR(cdev, "Enable endpoint FAILED!\n");
+			ERROR(cdev, "Enable IN endpoint FAILED!\n");
 			goto fail;
 		}
 		hidg->in_ep->driver_data = hidg;
 	}
+
+
+	if (hidg->out_ep != NULL) {
+		/* restart endpoint */
+		if (hidg->out_ep->driver_data != NULL)
+			usb_ep_disable(hidg->out_ep);
+
+		status = config_ep_by_speed(f->config->cdev->gadget, f,
+					    hidg->out_ep);
+		if (status) {
+			ERROR(cdev, "config_ep_by_speed FAILED!\n");
+			goto fail;
+		}
+		status = usb_ep_enable(hidg->out_ep);
+		if (status < 0) {
+			ERROR(cdev, "Enable IN endpoint FAILED!\n");
+			goto fail;
+		}
+		hidg->out_ep->driver_data = hidg;
+
+		/*
+		 * allocate a bunch of read buffers and queue them all at once.
+		 */
+		for (i = 0; i < hidg->qlen && status == 0; i++) {
+			struct usb_request *req =
+					hidg_alloc_ep_req(hidg->out_ep,
+							  hidg->report_length);
+			if (req) {
+				req->complete = hidg_set_report_complete;
+				req->context  = hidg;
+				status = usb_ep_queue(hidg->out_ep, req,
+						      GFP_ATOMIC);
+				if (status)
+					ERROR(cdev, "%s queue req --> %d\n",
+						hidg->out_ep->name, status);
+			} else {
+				usb_ep_disable(hidg->out_ep);
+				hidg->out_ep->driver_data = NULL;
+				status = -ENOMEM;
+				goto fail;
+			}
+		}
+	}
+
 fail:
 	return status;
 }
@@ -470,13 +582,18 @@ static int __init hidg_bind(struct usb_configuration *c, struct usb_function *f)
 	ep->driver_data = c->cdev;	/* claim */
 	hidg->in_ep = ep;
 
+	ep = usb_ep_autoconfig(c->cdev->gadget, &hidg_fs_out_ep_desc);
+	if (!ep)
+		goto fail;
+	ep->driver_data = c->cdev;	/* claim */
+	hidg->out_ep = ep;
+
 	/* preallocate request and buffer */
 	status = -ENOMEM;
 	hidg->req = usb_ep_alloc_request(hidg->in_ep, GFP_KERNEL);
 	if (!hidg->req)
 		goto fail;
 
-
 	hidg->req->buf = kmalloc(hidg->report_length, GFP_KERNEL);
 	if (!hidg->req->buf)
 		goto fail;
@@ -486,12 +603,12 @@ static int __init hidg_bind(struct usb_configuration *c, struct usb_function *f)
 	hidg_interface_desc.bInterfaceProtocol = hidg->bInterfaceProtocol;
 	hidg_hs_in_ep_desc.wMaxPacketSize = cpu_to_le16(hidg->report_length);
 	hidg_fs_in_ep_desc.wMaxPacketSize = cpu_to_le16(hidg->report_length);
+	hidg_hs_out_ep_desc.wMaxPacketSize = cpu_to_le16(hidg->report_length);
+	hidg_fs_out_ep_desc.wMaxPacketSize = cpu_to_le16(hidg->report_length);
 	hidg_desc.desc[0].bDescriptorType = HID_DT_REPORT;
 	hidg_desc.desc[0].wDescriptorLength =
 		cpu_to_le16(hidg->report_desc_length);
 
-	hidg->set_report_buff = NULL;
-
 	/* copy descriptors */
 	f->descriptors = usb_copy_descriptors(hidg_fs_descriptors);
 	if (!f->descriptors)
@@ -500,6 +617,8 @@ static int __init hidg_bind(struct usb_configuration *c, struct usb_function *f)
 	if (gadget_is_dualspeed(c->cdev->gadget)) {
 		hidg_hs_in_ep_desc.bEndpointAddress =
 			hidg_fs_in_ep_desc.bEndpointAddress;
+		hidg_hs_out_ep_desc.bEndpointAddress =
+			hidg_fs_out_ep_desc.bEndpointAddress;
 		f->hs_descriptors = usb_copy_descriptors(hidg_hs_descriptors);
 		if (!f->hs_descriptors)
 			goto fail;
@@ -509,6 +628,7 @@ static int __init hidg_bind(struct usb_configuration *c, struct usb_function *f)
 	spin_lock_init(&hidg->spinlock);
 	init_waitqueue_head(&hidg->write_queue);
 	init_waitqueue_head(&hidg->read_queue);
+	INIT_LIST_HEAD(&hidg->completed_out_req);
 
 	/* create char device */
 	cdev_init(&hidg->cdev, &f_hidg_fops);
@@ -553,7 +673,6 @@ static void hidg_unbind(struct usb_configuration *c, struct usb_function *f)
 	usb_free_descriptors(f->descriptors);
 
 	kfree(hidg->report_desc);
-	kfree(hidg->set_report_buff);
 	kfree(hidg);
 }
 
@@ -624,6 +743,9 @@ int __init hidg_bind_config(struct usb_configuration *c,
 	hidg->func.disable = hidg_disable;
 	hidg->func.setup   = hidg_setup;
 
+	/* this could me made configurable at some point */
+	hidg->qlen	   = 4;
+
 	status = usb_add_function(c, &hidg->func);
 	if (status)
 		kfree(hidg);