Merge tag 'usb-for-v4.13' of git://git.kernel.org/pub/scm/linux/kernel/git/balbi/usb into usb-testing

Felipe writes:

usb: changes for v4.13 merge window

This time around we have a total of 57 non-merge commits. A list of
most important changes follows:

- Improvements to dwc3 tracing interface
- Initial dual-role support for dwc3
- Improvements to how we handle DMA resources in dwc3
- A new f_uac1 implementation which much more flexible
- Removal of AVR32 bits
- Improvements to f_mass_storage driver

1 files changed, 173 insertions, 126 deletions

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index aea9a5b..9e41605a 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -1,4 +1,4 @@
-/**
+/*
  * gadget.c - DesignWare USB3 DRD Controller Gadget Framework Link
  *
  * Copyright (C) 2010-2011 Texas Instruments Incorporated - http://www.ti.com
@@ -36,13 +36,12 @@
 #include "io.h"
 
 /**
- * dwc3_gadget_set_test_mode - Enables USB2 Test Modes
+ * dwc3_gadget_set_test_mode - enables usb2 test modes
  * @dwc: pointer to our context structure
  * @mode: the mode to set (J, K SE0 NAK, Force Enable)
  *
- * Caller should take care of locking. This function will
- * return 0 on success or -EINVAL if wrong Test Selector
- * is passed
+ * Caller should take care of locking. This function will return 0 on
+ * success or -EINVAL if wrong Test Selector is passed.
  */
 int dwc3_gadget_set_test_mode(struct dwc3 *dwc, int mode)
 {
@@ -69,7 +68,7 @@ int dwc3_gadget_set_test_mode(struct dwc3 *dwc, int mode)
 }
 
 /**
- * dwc3_gadget_get_link_state - Gets current state of USB Link
+ * dwc3_gadget_get_link_state - gets current state of usb link
  * @dwc: pointer to our context structure
  *
  * Caller should take care of locking. This function will
@@ -85,7 +84,7 @@ int dwc3_gadget_get_link_state(struct dwc3 *dwc)
 }
 
 /**
- * dwc3_gadget_set_link_state - Sets USB Link to a particular State
+ * dwc3_gadget_set_link_state - sets usb link to a particular state
  * @dwc: pointer to our context structure
  * @state: the state to put link into
  *
@@ -143,8 +142,8 @@ int dwc3_gadget_set_link_state(struct dwc3 *dwc, enum dwc3_link_state state)
 }
 
 /**
- * dwc3_ep_inc_trb() - Increment a TRB index.
- * @index - Pointer to the TRB index to increment.
+ * dwc3_ep_inc_trb - increment a trb index.
+ * @index: Pointer to the TRB index to increment.
  *
  * The index should never point to the link TRB. After incrementing,
  * if it is point to the link TRB, wrap around to the beginning. The
@@ -157,16 +156,34 @@ static void dwc3_ep_inc_trb(u8 *index)
 		*index = 0;
 }
 
+/**
+ * dwc3_ep_inc_enq - increment endpoint's enqueue pointer
+ * @dep: The endpoint whose enqueue pointer we're incrementing
+ */
 static void dwc3_ep_inc_enq(struct dwc3_ep *dep)
 {
 	dwc3_ep_inc_trb(&dep->trb_enqueue);
 }
 
+/**
+ * dwc3_ep_inc_deq - increment endpoint's dequeue pointer
+ * @dep: The endpoint whose enqueue pointer we're incrementing
+ */
 static void dwc3_ep_inc_deq(struct dwc3_ep *dep)
 {
 	dwc3_ep_inc_trb(&dep->trb_dequeue);
 }
 
+/**
+ * dwc3_gadget_giveback - call struct usb_request's ->complete callback
+ * @dep: The endpoint to whom the request belongs to
+ * @req: The request we're giving back
+ * @status: completion code for the request
+ *
+ * Must be called with controller's lock held and interrupts disabled. This
+ * function will unmap @req and call its ->complete() callback to notify upper
+ * layers that it has completed.
+ */
 void dwc3_gadget_giveback(struct dwc3_ep *dep, struct dwc3_request *req,
 		int status)
 {
@@ -193,6 +210,15 @@ void dwc3_gadget_giveback(struct dwc3_ep *dep, struct dwc3_request *req,
 		pm_runtime_put(dwc->dev);
 }
 
+/**
+ * dwc3_send_gadget_generic_command - issue a generic command for the controller
+ * @dwc: pointer to the controller context
+ * @cmd: the command to be issued
+ * @param: command parameter
+ *
+ * Caller should take care of locking. Issue @cmd with a given @param to @dwc
+ * and wait for its completion.
+ */
 int dwc3_send_gadget_generic_command(struct dwc3 *dwc, unsigned cmd, u32 param)
 {
 	u32		timeout = 500;
@@ -225,6 +251,15 @@ int dwc3_send_gadget_generic_command(struct dwc3 *dwc, unsigned cmd, u32 param)
 
 static int __dwc3_gadget_wakeup(struct dwc3 *dwc);
 
+/**
+ * dwc3_send_gadget_ep_cmd - issue an endpoint command
+ * @dep: the endpoint to which the command is going to be issued
+ * @cmd: the command to be issued
+ * @params: parameters to the command
+ *
+ * Caller should handle locking. This function will issue @cmd with given
+ * @params to @dep and wait for its completion.
+ */
 int dwc3_send_gadget_ep_cmd(struct dwc3_ep *dep, unsigned cmd,
 		struct dwc3_gadget_ep_cmd_params *params)
 {
@@ -422,36 +457,38 @@ static void dwc3_free_trb_pool(struct dwc3_ep *dep)
 static int dwc3_gadget_set_xfer_resource(struct dwc3 *dwc, struct dwc3_ep *dep);
 
 /**
- * dwc3_gadget_start_config - Configure EP resources
+ * dwc3_gadget_start_config - configure ep resources
  * @dwc: pointer to our controller context structure
  * @dep: endpoint that is being enabled
  *
- * The assignment of transfer resources cannot perfectly follow the
- * data book due to the fact that the controller driver does not have
- * all knowledge of the configuration in advance. It is given this
- * information piecemeal by the composite gadget framework after every
- * SET_CONFIGURATION and SET_INTERFACE. Trying to follow the databook
- * programming model in this scenario can cause errors. For two
- * reasons:
+ * Issue a %DWC3_DEPCMD_DEPSTARTCFG command to @dep. After the command's
+ * completion, it will set Transfer Resource for all available endpoints.
  *
- * 1) The databook says to do DEPSTARTCFG for every SET_CONFIGURATION
- * and SET_INTERFACE (8.1.5). This is incorrect in the scenario of
- * multiple interfaces.
+ * The assignment of transfer resources cannot perfectly follow the data book
+ * due to the fact that the controller driver does not have all knowledge of the
+ * configuration in advance. It is given this information piecemeal by the
+ * composite gadget framework after every SET_CONFIGURATION and
+ * SET_INTERFACE. Trying to follow the databook programming model in this
+ * scenario can cause errors. For two reasons:
  *
- * 2) The databook does not mention doing more DEPXFERCFG for new
+ * 1) The databook says to do %DWC3_DEPCMD_DEPSTARTCFG for every
+ * %USB_REQ_SET_CONFIGURATION and %USB_REQ_SET_INTERFACE (8.1.5). This is
+ * incorrect in the scenario of multiple interfaces.
+ *
+ * 2) The databook does not mention doing more %DWC3_DEPCMD_DEPXFERCFG for new
  * endpoint on alt setting (8.1.6).
  *
  * The following simplified method is used instead:
  *
- * All hardware endpoints can be assigned a transfer resource and this
- * setting will stay persistent until either a core reset or
- * hibernation. So whenever we do a DEPSTARTCFG(0) we can go ahead and
- * do DEPXFERCFG for every hardware endpoint as well. We are
+ * All hardware endpoints can be assigned a transfer resource and this setting
+ * will stay persistent until either a core reset or hibernation. So whenever we
+ * do a %DWC3_DEPCMD_DEPSTARTCFG(0) we can go ahead and do
+ * %DWC3_DEPCMD_DEPXFERCFG for every hardware endpoint as well. We are
  * guaranteed that there are as many transfer resources as endpoints.
  *
- * This function is called for each endpoint when it is being enabled
- * but is triggered only when called for EP0-out, which always happens
- * first, and which should only happen in one of the above conditions.
+ * This function is called for each endpoint when it is being enabled but is
+ * triggered only when called for EP0-out, which always happens first, and which
+ * should only happen in one of the above conditions.
  */
 static int dwc3_gadget_start_config(struct dwc3 *dwc, struct dwc3_ep *dep)
 {
@@ -569,11 +606,13 @@ static int dwc3_gadget_set_xfer_resource(struct dwc3 *dwc, struct dwc3_ep *dep)
 }
 
 /**
- * __dwc3_gadget_ep_enable - Initializes a HW endpoint
+ * __dwc3_gadget_ep_enable - initializes a hw endpoint
  * @dep: endpoint to be initialized
- * @desc: USB Endpoint Descriptor
+ * @modify: if true, modify existing endpoint configuration
+ * @restore: if true, restore endpoint configuration from scratch buffer
  *
- * Caller should take care of locking
+ * Caller should take care of locking. Execute all necessary commands to
+ * initialize a HW endpoint so it can be used by a gadget driver.
  */
 static int __dwc3_gadget_ep_enable(struct dwc3_ep *dep,
 		bool modify, bool restore)
@@ -685,11 +724,13 @@ static void dwc3_remove_requests(struct dwc3 *dwc, struct dwc3_ep *dep)
 }
 
 /**
- * __dwc3_gadget_ep_disable - Disables a HW endpoint
+ * __dwc3_gadget_ep_disable - disables a hw endpoint
  * @dep: the endpoint to disable
  *
- * This function also removes requests which are currently processed ny the
- * hardware and those which are not yet scheduled.
+ * This function undoes what __dwc3_gadget_ep_enable did and also removes
+ * requests which are currently being processed by the hardware and those which
+ * are not yet scheduled.
+ *
  * Caller should take care of locking.
  */
 static int __dwc3_gadget_ep_disable(struct dwc3_ep *dep)
@@ -932,7 +973,7 @@ static void dwc3_prepare_one_trb(struct dwc3_ep *dep,
 }
 
 /**
- * dwc3_ep_prev_trb() - Returns the previous TRB in the ring
+ * dwc3_ep_prev_trb - returns the previous TRB in the ring
  * @dep: The endpoint with the TRB ring
  * @index: The index of the current TRB in the ring
  *
@@ -953,7 +994,6 @@ static struct dwc3_trb *dwc3_ep_prev_trb(struct dwc3_ep *dep, u8 index)
 static u32 dwc3_calc_trbs_left(struct dwc3_ep *dep)
 {
 	struct dwc3_trb		*tmp;
-	struct dwc3		*dwc = dep->dwc;
 	u8			trbs_left;
 
 	/*
@@ -965,8 +1005,7 @@ static u32 dwc3_calc_trbs_left(struct dwc3_ep *dep)
 	 */
 	if (dep->trb_enqueue == dep->trb_dequeue) {
 		tmp = dwc3_ep_prev_trb(dep, dep->trb_enqueue);
-		if (dev_WARN_ONCE(dwc->dev, tmp->ctrl & DWC3_TRB_CTRL_HWO,
-				  "%s No TRBS left\n", dep->name))
+		if (tmp->ctrl & DWC3_TRB_CTRL_HWO)
 			return 0;
 
 		return DWC3_TRB_NUM - 1;
@@ -1101,6 +1140,17 @@ static void dwc3_prepare_trbs(struct dwc3_ep *dep)
 	}
 
 	list_for_each_entry_safe(req, n, &dep->pending_list, list) {
+		struct dwc3	*dwc = dep->dwc;
+		int		ret;
+
+		ret = usb_gadget_map_request_by_dev(dwc->sysdev, &req->request,
+						    dep->direction);
+		if (ret)
+			return;
+
+		req->sg			= req->request.sg;
+		req->num_pending_sgs	= req->request.num_mapped_sgs;
+
 		if (req->num_pending_sgs > 0)
 			dwc3_prepare_one_trb_sg(dep, req);
 		else
@@ -1207,7 +1257,7 @@ static void dwc3_gadget_start_isoc(struct dwc3 *dwc,
 static int __dwc3_gadget_ep_queue(struct dwc3_ep *dep, struct dwc3_request *req)
 {
 	struct dwc3		*dwc = dep->dwc;
-	int			ret;
+	int			ret = 0;
 
 	if (!dep->endpoint.desc) {
 		dev_err(dwc->dev, "%s: can't queue to disabled endpoint\n",
@@ -1215,12 +1265,9 @@ static int __dwc3_gadget_ep_queue(struct dwc3_ep *dep, struct dwc3_request *req)
 		return -ESHUTDOWN;
 	}
 
-	if (WARN(req->dep != dep, "request %p belongs to '%s'\n",
-				&req->request, req->dep->name)) {
-		dev_err(dwc->dev, "%s: request %p belongs to '%s'\n",
-				dep->name, &req->request, req->dep->name);
+	if (WARN(req->dep != dep, "request %pK belongs to '%s'\n",
+				&req->request, req->dep->name))
 		return -EINVAL;
-	}
 
 	pm_runtime_get(dwc->dev);
 
@@ -1231,14 +1278,6 @@ static int __dwc3_gadget_ep_queue(struct dwc3_ep *dep, struct dwc3_request *req)
 
 	trace_dwc3_ep_queue(req);
 
-	ret = usb_gadget_map_request_by_dev(dwc->sysdev, &req->request,
-					    dep->direction);
-	if (ret)
-		return ret;
-
-	req->sg			= req->request.sg;
-	req->num_pending_sgs	= req->request.num_mapped_sgs;
-
 	list_add_tail(&req->list, &dep->pending_list);
 
 	/*
@@ -1396,7 +1435,7 @@ static int dwc3_gadget_ep_dequeue(struct usb_ep *ep,
 			}
 			goto out1;
 		}
-		dev_err(dwc->dev, "request %p was not queued to %s\n",
+		dev_err(dwc->dev, "request %pK was not queued to %s\n",
 				request, ep->name);
 		ret = -EINVAL;
 		goto out0;
@@ -1741,8 +1780,8 @@ static irqreturn_t dwc3_interrupt(int irq, void *_dwc);
 static irqreturn_t dwc3_thread_interrupt(int irq, void *_dwc);
 
 /**
- * dwc3_gadget_setup_nump - Calculate and initialize NUMP field of DCFG
- * dwc: pointer to our context structure
+ * dwc3_gadget_setup_nump - calculate and initialize NUMP field of %DWC3_DCFG
+ * @dwc: pointer to our context structure
  *
  * The following looks like complex but it's actually very simple. In order to
  * calculate the number of packets we can burst at once on OUT transfers, we're
@@ -1798,49 +1837,6 @@ static int __dwc3_gadget_start(struct dwc3 *dwc)
 		dwc3_writel(dwc->regs, DWC3_DEV_IMOD(0), 0);
 	}
 
-	reg = dwc3_readl(dwc->regs, DWC3_DCFG);
-	reg &= ~(DWC3_DCFG_SPEED_MASK);
-
-	/**
-	 * WORKAROUND: DWC3 revision < 2.20a have an issue
-	 * which would cause metastability state on Run/Stop
-	 * bit if we try to force the IP to USB2-only mode.
-	 *
-	 * Because of that, we cannot configure the IP to any
-	 * speed other than the SuperSpeed
-	 *
-	 * Refers to:
-	 *
-	 * STAR#9000525659: Clock Domain Crossing on DCTL in
-	 * USB 2.0 Mode
-	 */
-	if (dwc->revision < DWC3_REVISION_220A) {
-		reg |= DWC3_DCFG_SUPERSPEED;
-	} else {
-		switch (dwc->maximum_speed) {
-		case USB_SPEED_LOW:
-			reg |= DWC3_DCFG_LOWSPEED;
-			break;
-		case USB_SPEED_FULL:
-			reg |= DWC3_DCFG_FULLSPEED;
-			break;
-		case USB_SPEED_HIGH:
-			reg |= DWC3_DCFG_HIGHSPEED;
-			break;
-		case USB_SPEED_SUPER_PLUS:
-			reg |= DWC3_DCFG_SUPERSPEED_PLUS;
-			break;
-		default:
-			dev_err(dwc->dev, "invalid dwc->maximum_speed (%d)\n",
-				dwc->maximum_speed);
-			/* fall through */
-		case USB_SPEED_SUPER:
-			reg |= DWC3_DCFG_SUPERSPEED;
-			break;
-		}
-	}
-	dwc3_writel(dwc->regs, DWC3_DCFG, reg);
-
 	/*
 	 * We are telling dwc3 that we want to use DCFG.NUMP as ACK TP's NUMP
 	 * field instead of letting dwc3 itself calculate that automatically.
@@ -1972,6 +1968,63 @@ out:
 	return 0;
 }
 
+static void dwc3_gadget_set_speed(struct usb_gadget *g,
+				  enum usb_device_speed speed)
+{
+	struct dwc3		*dwc = gadget_to_dwc(g);
+	unsigned long		flags;
+	u32			reg;
+
+	spin_lock_irqsave(&dwc->lock, flags);
+	reg = dwc3_readl(dwc->regs, DWC3_DCFG);
+	reg &= ~(DWC3_DCFG_SPEED_MASK);
+
+	/*
+	 * WORKAROUND: DWC3 revision < 2.20a have an issue
+	 * which would cause metastability state on Run/Stop
+	 * bit if we try to force the IP to USB2-only mode.
+	 *
+	 * Because of that, we cannot configure the IP to any
+	 * speed other than the SuperSpeed
+	 *
+	 * Refers to:
+	 *
+	 * STAR#9000525659: Clock Domain Crossing on DCTL in
+	 * USB 2.0 Mode
+	 */
+	if (dwc->revision < DWC3_REVISION_220A) {
+		reg |= DWC3_DCFG_SUPERSPEED;
+	} else {
+		switch (speed) {
+		case USB_SPEED_LOW:
+			reg |= DWC3_DCFG_LOWSPEED;
+			break;
+		case USB_SPEED_FULL:
+			reg |= DWC3_DCFG_FULLSPEED;
+			break;
+		case USB_SPEED_HIGH:
+			reg |= DWC3_DCFG_HIGHSPEED;
+			break;
+		case USB_SPEED_SUPER:
+			reg |= DWC3_DCFG_SUPERSPEED;
+			break;
+		case USB_SPEED_SUPER_PLUS:
+			reg |= DWC3_DCFG_SUPERSPEED_PLUS;
+			break;
+		default:
+			dev_err(dwc->dev, "invalid speed (%d)\n", speed);
+
+			if (dwc->revision & DWC3_REVISION_IS_DWC31)
+				reg |= DWC3_DCFG_SUPERSPEED_PLUS;
+			else
+				reg |= DWC3_DCFG_SUPERSPEED;
+		}
+	}
+	dwc3_writel(dwc->regs, DWC3_DCFG, reg);
+
+	spin_unlock_irqrestore(&dwc->lock, flags);
+}
+
 static const struct usb_gadget_ops dwc3_gadget_ops = {
 	.get_frame		= dwc3_gadget_get_frame,
 	.wakeup			= dwc3_gadget_wakeup,
@@ -1979,19 +2032,21 @@ static const struct usb_gadget_ops dwc3_gadget_ops = {
 	.pullup			= dwc3_gadget_pullup,
 	.udc_start		= dwc3_gadget_start,
 	.udc_stop		= dwc3_gadget_stop,
+	.udc_set_speed		= dwc3_gadget_set_speed,
 };
 
 /* -------------------------------------------------------------------------- */
 
-static int dwc3_gadget_init_endpoints(struct dwc3 *dwc, u8 num)
+static int dwc3_gadget_init_endpoints(struct dwc3 *dwc, u8 total)
 {
 	struct dwc3_ep			*dep;
 	u8				epnum;
 
 	INIT_LIST_HEAD(&dwc->gadget.ep_list);
 
-	for (epnum = 0; epnum < num; epnum++) {
+	for (epnum = 0; epnum < total; epnum++) {
 		bool			direction = epnum & 1;
+		u8			num = epnum >> 1;
 
 		dep = kzalloc(sizeof(*dep), GFP_KERNEL);
 		if (!dep)
@@ -2003,7 +2058,7 @@ static int dwc3_gadget_init_endpoints(struct dwc3 *dwc, u8 num)
 		dep->regs = dwc->regs + DWC3_DEP_BASE(epnum);
 		dwc->eps[epnum] = dep;
 
-		snprintf(dep->name, sizeof(dep->name), "ep%d%s", epnum >> 1,
+		snprintf(dep->name, sizeof(dep->name), "ep%u%s", num,
 				direction ? "in" : "out");
 
 		dep->endpoint.name = dep->name;
@@ -2015,39 +2070,39 @@ static int dwc3_gadget_init_endpoints(struct dwc3 *dwc, u8 num)
 
 		spin_lock_init(&dep->lock);
 
-		if (epnum == 0 || epnum == 1) {
+		if (num == 0) {
 			usb_ep_set_maxpacket_limit(&dep->endpoint, 512);
 			dep->endpoint.maxburst = 1;
 			dep->endpoint.ops = &dwc3_gadget_ep0_ops;
-			if (!epnum)
+			if (!direction)
 				dwc->gadget.ep0 = &dep->endpoint;
 		} else if (direction) {
 			int mdwidth;
+			int kbytes;
 			int size;
 			int ret;
-			int num;
 
 			mdwidth = DWC3_MDWIDTH(dwc->hwparams.hwparams0);
 			/* MDWIDTH is represented in bits, we need it in bytes */
 			mdwidth /= 8;
 
-			size = dwc3_readl(dwc->regs, DWC3_GTXFIFOSIZ(epnum >> 1));
+			size = dwc3_readl(dwc->regs, DWC3_GTXFIFOSIZ(num));
 			size = DWC3_GTXFIFOSIZ_TXFDEF(size);
 
 			/* FIFO Depth is in MDWDITH bytes. Multiply */
 			size *= mdwidth;
 
-			num = size / 1024;
-			if (num == 0)
-				num = 1;
+			kbytes = size / 1024;
+			if (kbytes == 0)
+				kbytes = 1;
 
 			/*
-			 * FIFO sizes account an extra MDWIDTH * (num + 1) bytes for
+			 * FIFO sizes account an extra MDWIDTH * (kbytes + 1) bytes for
 			 * internal overhead. We don't really know how these are used,
 			 * but documentation say it exists.
 			 */
-			size -= mdwidth * (num + 1);
-			size /= num;
+			size -= mdwidth * (kbytes + 1);
+			size /= kbytes;
 
 			usb_ep_set_maxpacket_limit(&dep->endpoint, size);
 
@@ -2073,7 +2128,7 @@ static int dwc3_gadget_init_endpoints(struct dwc3 *dwc, u8 num)
 				return ret;
 		}
 
-		if (epnum == 0 || epnum == 1) {
+		if (num == 0) {
 			dep->endpoint.caps.type_control = true;
 		} else {
 			dep->endpoint.caps.type_iso = true;
@@ -2871,7 +2926,7 @@ static void dwc3_gadget_hibernation_interrupt(struct dwc3 *dwc,
 {
 	unsigned int is_ss = evtinfo & BIT(4);
 
-	/**
+	/*
 	 * WORKAROUND: DWC3 revison 2.20a with hibernation support
 	 * have a known issue which can cause USB CV TD.9.23 to fail
 	 * randomly.
@@ -2943,20 +2998,12 @@ static void dwc3_process_event_entry(struct dwc3 *dwc,
 {
 	trace_dwc3_event(event->raw, dwc);
 
-	/* Endpoint IRQ, handle it and return early */
-	if (event->type.is_devspec == 0) {
-		/* depevt */
-		return dwc3_endpoint_interrupt(dwc, &event->depevt);
-	}
-
-	switch (event->type.type) {
-	case DWC3_EVENT_TYPE_DEV:
+	if (!event->type.is_devspec)
+		dwc3_endpoint_interrupt(dwc, &event->depevt);
+	else if (event->type.type == DWC3_EVENT_TYPE_DEV)
 		dwc3_gadget_interrupt(dwc, &event->devt);
-		break;
-	/* REVISIT what to do with Carkit and I2C events ? */
-	default:
+	else
 		dev_err(dwc->dev, "UNKNOWN IRQ type %d\n", event->raw);
-	}
 }
 
 static irqreturn_t dwc3_process_event_buf(struct dwc3_event_buffer *evt)
@@ -3110,7 +3157,7 @@ out:
 }
 
 /**
- * dwc3_gadget_init - Initializes gadget related registers
+ * dwc3_gadget_init - initializes gadget related registers
  * @dwc: pointer to our controller context structure
  *
  * Returns 0 on success otherwise negative errno.