/*
 * Wireless Host Controller (WHC) qset management.
 *
 * Copyright (C) 2007 Cambridge Silicon Radio Ltd.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License version
 * 2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
#include <linux/kernel.h>
#include <linux/dma-mapping.h>
#include <linux/slab.h>
#include <linux/uwb/umc.h>
#include <linux/usb.h>

#include "../../wusbcore/wusbhc.h"

#include "whcd.h"

struct whc_qset *qset_alloc(struct whc *whc, gfp_t mem_flags)
{
	struct whc_qset *qset;
	dma_addr_t dma;

	qset = dma_pool_zalloc(whc->qset_pool, mem_flags, &dma);
	if (qset == NULL)
		return NULL;

	qset->qset_dma = dma;
	qset->whc = whc;

	INIT_LIST_HEAD(&qset->list_node);
	INIT_LIST_HEAD(&qset->stds);

	return qset;
}

/**
 * qset_fill_qh - fill the static endpoint state in a qset's QHead
 * @qset: the qset whose QH needs initializing with static endpoint
 *        state
 * @urb:  an urb for a transfer to this endpoint
 */
static void qset_fill_qh(struct whc *whc, struct whc_qset *qset, struct urb *urb)
{
	struct usb_device *usb_dev = urb->dev;
	struct wusb_dev *wusb_dev = usb_dev->wusb_dev;
	struct usb_wireless_ep_comp_descriptor *epcd;
	bool is_out;
	uint8_t phy_rate;

	is_out = usb_pipeout(urb->pipe);

	qset->max_packet = le16_to_cpu(urb->ep->desc.wMaxPacketSize);

	epcd = (struct usb_wireless_ep_comp_descriptor *)qset->ep->extra;
	if (epcd) {
		qset->max_seq = epcd->bMaxSequence;
		qset->max_burst = epcd->bMaxBurst;
	} else {
		qset->max_seq = 2;
		qset->max_burst = 1;
	}

	/*
	 * Initial PHY rate is 53.3 Mbit/s for control endpoints or
	 * the maximum supported by the device for other endpoints
	 * (unless limited by the user).
	 */
	if (usb_pipecontrol(urb->pipe))
		phy_rate = UWB_PHY_RATE_53;
	else {
		uint16_t phy_rates;

		phy_rates = le16_to_cpu(wusb_dev->wusb_cap_descr->wPHYRates);
		phy_rate = fls(phy_rates) - 1;
		if (phy_rate > whc->wusbhc.phy_rate)
			phy_rate = whc->wusbhc.phy_rate;
	}

	qset->qh.info1 = cpu_to_le32(
		QH_INFO1_EP(usb_pipeendpoint(urb->pipe))
		| (is_out ? QH_INFO1_DIR_OUT : QH_INFO1_DIR_IN)
		| usb_pipe_to_qh_type(urb->pipe)
		| QH_INFO1_DEV_INFO_IDX(wusb_port_no_to_idx(usb_dev->portnum))
		| QH_INFO1_MAX_PKT_LEN(qset->max_packet)
		);
	qset->qh.info2 = cpu_to_le32(
		QH_INFO2_BURST(qset->max_burst)
		| QH_INFO2_DBP(0)
		| QH_INFO2_MAX_COUNT(3)
		| QH_INFO2_MAX_RETRY(3)
		| QH_INFO2_MAX_SEQ(qset->max_seq - 1)
		);
	/* FIXME: where can we obtain these Tx parameters from?  Why
	 * doesn't the chip know what Tx power to use? It knows the Rx
	 * strength and can presumably guess the Tx power required
	 * from that? */
	qset->qh.info3 = cpu_to_le32(
		QH_INFO3_TX_RATE(phy_rate)
		| QH_INFO3_TX_PWR(0) /* 0 == max power */
		);

	qset->qh.cur_window = cpu_to_le32((1 << qset->max_burst) - 1);
}

/**
 * qset_clear - clear fields in a qset so it may be reinserted into a
 * schedule.
 *
 * The sequence number and current window are not cleared (see
 * qset_reset()).
 */
void qset_clear(struct whc *whc, struct whc_qset *qset)
{
	qset->td_start = qset->td_end = qset->ntds = 0;

	qset->qh.link = cpu_to_le64(QH_LINK_NTDS(8) | QH_LINK_T);
	qset->qh.status = qset->qh.status & QH_STATUS_SEQ_MASK;
	qset->qh.err_count = 0;
	qset->qh.scratch[0] = 0;
	qset->qh.scratch[1] = 0;
	qset->qh.scratch[2] = 0;

	memset(&qset->qh.overlay, 0, sizeof(qset->qh.overlay));

	init_completion(&qset->remove_complete);
}

/**
 * qset_reset - reset endpoint state in a qset.
 *
 * Clears the sequence number and current window.  This qset must not
 * be in the ASL or PZL.
 */
void qset_reset(struct whc *whc, struct whc_qset *qset)
{
	qset->reset = 0;

	qset->qh.status &= ~QH_STATUS_SEQ_MASK;
	qset->qh.cur_window = cpu_to_le32((1 << qset->max_burst) - 1);
}

/**
 * get_qset - get the qset for an async endpoint
 *
 * A new qset is created if one does not already exist.
 */
struct whc_qset *get_qset(struct whc *whc, struct urb *urb,
				 gfp_t mem_flags)
{
	struct whc_qset *qset;

	qset = urb->ep->hcpriv;
	if (qset == NULL) {
		qset = qset_alloc(whc, mem_flags);
		if (qset == NULL)
			return NULL;

		qset->ep = urb->ep;
		urb->ep->hcpriv = qset;
		qset_fill_qh(whc, qset, urb);
	}
	return qset;
}

void qset_remove_complete(struct whc *whc, struct whc_qset *qset)
{
	qset->remove = 0;
	list_del_init(&qset->list_node);
	complete(&qset->remove_complete);
}

/**
 * qset_add_qtds - add qTDs for an URB to a qset
 *
 * Returns true if the list (ASL/PZL) must be updated because (for a
 * WHCI 0.95 controller) an activated qTD was pointed to be iCur.
 */
enum whc_update qset_add_qtds(struct whc *whc, struct whc_qset *qset)
{
	struct whc_std *std;
	enum whc_update update = 0;

	list_for_each_entry(std, &qset->stds, list_node) {
		struct whc_qtd *qtd;
		uint32_t status;

		if (qset->ntds >= WHCI_QSET_TD_MAX
		    || (qset->pause_after_urb && std->urb != qset->pause_after_urb))
			break;

		if (std->qtd)
			continue; /* already has a qTD */

		qtd = std->qtd = &qset->qtd[qset->td_end];

		/* Fill in setup bytes for control transfers. */
		if (usb_pipecontrol(std->urb->pipe))
			memcpy(qtd->setup, std->urb->setup_packet, 8);

		status = QTD_STS_ACTIVE | QTD_STS_LEN(std->len);

		if (whc_std_last(std) && usb_pipeout(std->urb->pipe))
			status |= QTD_STS_LAST_PKT;

		/*
		 * For an IN transfer the iAlt field should be set so
		 * the h/w will automatically advance to the next
		 * transfer. However, if there are 8 or more TDs
		 * remaining in this transfer then iAlt cannot be set
		 * as it could point to somewhere in this transfer.
		 */
		if (std->ntds_remaining < WHCI_QSET_TD_MAX) {
			int ialt;
			ialt = (qset->td_end + std->ntds_remaining) % WHCI_QSET_TD_MAX;
			status |= QTD_STS_IALT(ialt);
		} else if (usb_pipein(std->urb->pipe))
			qset->pause_after_urb = std->urb;

		if (std->num_pointers)
			qtd->options = cpu_to_le32(QTD_OPT_IOC);
		else
			qtd->options = cpu_to_le32(QTD_OPT_IOC | QTD_OPT_SMALL);
		qtd->page_list_ptr = cpu_to_le64(std->dma_addr);

		qtd->status = cpu_to_le32(status);

		if (QH_STATUS_TO_ICUR(qset->qh.status) == qset->td_end)
			update = WHC_UPDATE_UPDATED;

		if (++qset->td_end >= WHCI_QSET_TD_MAX)
			qset->td_end = 0;
		qset->ntds++;
	}

	return update;
}

/**
 * qset_remove_qtd - remove the first qTD from a qset.
 *
 * The qTD might be still active (if it's part of a IN URB that
 * resulted in a short read) so ensure it's deactivated.
 */
static void qset_remove_qtd(struct whc *whc, struct whc_qset *qset)
{
	qset->qtd[qset->td_start].status = 0;

	if (++qset->td_start >= WHCI_QSET_TD_MAX)
		qset->td_start = 0;
	qset->ntds--;
}

static void qset_copy_bounce_to_sg(struct whc *whc, struct whc_std *std)
{
	struct scatterlist *sg;
	void *bounce;
	size_t remaining, offset;

	bounce = std->bounce_buf;
	remaining = std->len;

	sg = std->bounce_sg;
	offset = std->bounce_offset;

	while (remaining) {
		size_t len;

		len = min(sg->length - offset, remaining);
		memcpy(sg_virt(sg) + offset, bounce, len);

		bounce += len;
		remaining -= len;

		offset += len;
		if (offset >= sg->length) {
			sg = sg_next(sg);
			offset = 0;
		}
	}

}

/**
 * qset_free_std - remove an sTD and free it.
 * @whc: the WHCI host controller
 * @std: the sTD to remove and free.
 */
void qset_free_std(struct whc *whc, struct whc_std *std)
{
	list_del(&std->list_node);
	if (std->bounce_buf) {
		bool is_out = usb_pipeout(std->urb->pipe);
		dma_addr_t dma_addr;

		if (std->num_pointers)
			dma_addr = le64_to_cpu(std->pl_virt[0].buf_ptr);
		else
			dma_addr = std->dma_addr;

		dma_unmap_single(whc->wusbhc.dev, dma_addr,
				 std->len, is_out ? DMA_TO_DEVICE : DMA_FROM_DEVICE);
		if (!is_out)
			qset_copy_bounce_to_sg(whc, std);
		kfree(std->bounce_buf);
	}
	if (std->pl_virt) {
		if (!dma_mapping_error(whc->wusbhc.dev, std->dma_addr))
			dma_unmap_single(whc->wusbhc.dev, std->dma_addr,
					 std->num_pointers * sizeof(struct whc_page_list_entry),
					 DMA_TO_DEVICE);
		kfree(std->pl_virt);
		std->pl_virt = NULL;
	}
	kfree(std);
}

/**
 * qset_remove_qtds - remove an URB's qTDs (and sTDs).
 */
static void qset_remove_qtds(struct whc *whc, struct whc_qset *qset,
			     struct urb *urb)
{
	struct whc_std *std, *t;

	list_for_each_entry_safe(std, t, &qset->stds, list_node) {
		if (std->urb != urb)
			break;
		if (std->qtd != NULL)
			qset_remove_qtd(whc, qset);
		qset_free_std(whc, std);
	}
}

/**
 * qset_free_stds - free any remaining sTDs for an URB.
 */
static void qset_free_stds(struct whc_qset *qset, struct urb *urb)
{
	struct whc_std *std, *t;

	list_for_each_entry_safe(std, t, &qset->stds, list_node) {
		if (std->urb == urb)
			qset_free_std(qset->whc, std);
	}
}

static int qset_fill_page_list(struct whc *whc, struct whc_std *std, gfp_t mem_flags)
{
	dma_addr_t dma_addr = std->dma_addr;
	dma_addr_t sp, ep;
	size_t pl_len;
	int p;

	/* Short buffers don't need a page list. */
	if (std->len <= WHCI_PAGE_SIZE) {
		std->num_pointers = 0;
		return 0;
	}

	sp = dma_addr & ~(WHCI_PAGE_SIZE-1);
	ep = dma_addr + std->len;
	std->num_pointers = DIV_ROUND_UP(ep - sp, WHCI_PAGE_SIZE);

	pl_len = std->num_pointers * sizeof(struct whc_page_list_entry);
	std->pl_virt = kmalloc(pl_len, mem_flags);
	if (std->pl_virt == NULL)
		return -ENOMEM;
	std->dma_addr = dma_map_single(whc->wusbhc.dev, std->pl_virt, pl_len, DMA_TO_DEVICE);
	if (dma_mapping_error(whc->wusbhc.dev, std->dma_addr)) {
		kfree(std->pl_virt);
		return -EFAULT;
	}

	for (p = 0; p < std->num_pointers; p++) {
		std->pl_virt[p].buf_ptr = cpu_to_le64(dma_addr);
		dma_addr = (dma_addr + WHCI_PAGE_SIZE) & ~(WHCI_PAGE_SIZE-1);
	}

	return 0;
}

/**
 * urb_dequeue_work - executes asl/pzl update and gives back the urb to the system.
 */
static void urb_dequeue_work(struct work_struct *work)
{
	struct whc_urb *wurb = container_of(work, struct whc_urb, dequeue_work);
	struct whc_qset *qset = wurb->qset;
	struct whc *whc = qset->whc;
	unsigned long flags;

	if (wurb->is_async)
		asl_update(whc, WUSBCMD_ASYNC_UPDATED
			   | WUSBCMD_ASYNC_SYNCED_DB
			   | WUSBCMD_ASYNC_QSET_RM);
	else
		pzl_update(whc, WUSBCMD_PERIODIC_UPDATED
			   | WUSBCMD_PERIODIC_SYNCED_DB
			   | WUSBCMD_PERIODIC_QSET_RM);

	spin_lock_irqsave(&whc->lock, flags);
	qset_remove_urb(whc, qset, wurb->urb, wurb->status);
	spin_unlock_irqrestore(&whc->lock, flags);
}

static struct whc_std *qset_new_std(struct whc *whc, struct whc_qset *qset,
				    struct urb *urb, gfp_t mem_flags)
{
	struct whc_std *std;

	std = kzalloc(sizeof(struct whc_std), mem_flags);
	if (std == NULL)
		return NULL;

	std->urb = urb;
	std->qtd = NULL;

	INIT_LIST_HEAD(&std->list_node);
	list_add_tail(&std->list_node, &qset->stds);

	return std;
}

static int qset_add_urb_sg(struct whc *whc, struct whc_qset *qset, struct urb *urb,
			   gfp_t mem_flags)
{
	size_t remaining;
	struct scatterlist *sg;
	int i;
	int ntds = 0;
	struct whc_std *std = NULL;
	struct whc_page_list_entry *new_pl_virt;
	dma_addr_t prev_end = 0;
	size_t pl_len;
	int p = 0;

	remaining = urb->transfer_buffer_length;

	for_each_sg(urb->sg, sg, urb->num_mapped_sgs, i) {
		dma_addr_t dma_addr;
		size_t dma_remaining;
		dma_addr_t sp, ep;
		int num_pointers;

		if (remaining == 0) {
			break;
		}

		dma_addr = sg_dma_address(sg);
		dma_remaining = min_t(size_t, sg_dma_len(sg), remaining);

		while (dma_remaining) {
			size_t dma_len;

			/*
			 * We can use the previous std (if it exists) provided that:
			 * - the previous one ended on a page boundary.
			 * - the current one begins on a page boundary.
			 * - the previous one isn't full.
			 *
			 * If a new std is needed but the previous one
			 * was not a whole number of packets then this
			 * sg list cannot be mapped onto multiple
			 * qTDs.  Return an error and let the caller
			 * sort it out.
			 */
			if (!std
			    || (prev_end & (WHCI_PAGE_SIZE-1))
			    || (dma_addr & (WHCI_PAGE_SIZE-1))
			    || std->len + WHCI_PAGE_SIZE > QTD_MAX_XFER_SIZE) {
				if (std && std->len % qset->max_packet != 0)
					return -EINVAL;
				std = qset_new_std(whc, qset, urb, mem_flags);
				if (std == NULL) {
					return -ENOMEM;
				}
				ntds++;
				p = 0;
			}

			dma_len = dma_remaining;

			/*
			 * If the remainder of this element doesn't
			 * fit in a single qTD, limit the qTD to a
			 * whole number of packets.  This allows the
			 * remainder to go into the next qTD.
			 */
			if (std->len + dma_len > QTD_MAX_XFER_SIZE) {
				dma_len = (QTD_MAX_XFER_SIZE / qset->max_packet)
					* qset->max_packet - std->len;
			}

			std->len += dma_len;
			std->ntds_remaining = -1; /* filled in later */

			sp = dma_addr & ~(WHCI_PAGE_SIZE-1);
			ep = dma_addr + dma_len;
			num_pointers = DIV_ROUND_UP(ep - sp, WHCI_PAGE_SIZE);
			std->num_pointers += num_pointers;

			pl_len = std->num_pointers * sizeof(struct whc_page_list_entry);

			new_pl_virt = krealloc(std->pl_virt, pl_len, mem_flags);
			if (new_pl_virt == NULL) {
				kfree(std->pl_virt);
				std->pl_virt = NULL;
				return -ENOMEM;
			}
			std->pl_virt = new_pl_virt;

			for (;p < std->num_pointers; p++) {
				std->pl_virt[p].buf_ptr = cpu_to_le64(dma_addr);
				dma_addr = (dma_addr + WHCI_PAGE_SIZE) & ~(WHCI_PAGE_SIZE-1);
			}

			prev_end = dma_addr = ep;
			dma_remaining -= dma_len;
			remaining -= dma_len;
		}
	}

	/* Now the number of stds is know, go back and fill in
	   std->ntds_remaining. */
	list_for_each_entry(std, &qset->stds, list_node) {
		if (std->ntds_remaining == -1) {
			pl_len = std->num_pointers * sizeof(struct whc_page_list_entry);
			std->dma_addr = dma_map_single(whc->wusbhc.dev, std->pl_virt,
						       pl_len, DMA_TO_DEVICE);
			if (dma_mapping_error(whc->wusbhc.dev, std->dma_addr))
				return -EFAULT;
			std->ntds_remaining = ntds--;
		}
	}
	return 0;
}

/**
 * qset_add_urb_sg_linearize - add an urb with sg list, copying the data
 *
 * If the URB contains an sg list whose elements cannot be directly
 * mapped to qTDs then the data must be transferred via bounce
 * buffers.
 */
static int qset_add_urb_sg_linearize(struct whc *whc, struct whc_qset *qset,
				     struct urb *urb, gfp_t mem_flags)
{
	bool is_out = usb_pipeout(urb->pipe);
	size_t max_std_len;
	size_t remaining;
	int ntds = 0;
	struct whc_std *std = NULL;
	void *bounce = NULL;
	struct scatterlist *sg;
	int i;

	/* limit maximum bounce buffer to 16 * 3.5 KiB ~= 28 k */
	max_std_len = qset->max_burst * qset->max_packet;

	remaining = urb->transfer_buffer_length;

	for_each_sg(urb->sg, sg, urb->num_mapped_sgs, i) {
		size_t len;
		size_t sg_remaining;
		void *orig;

		if (remaining == 0) {
			break;
		}

		sg_remaining = min_t(size_t, remaining, sg->length);
		orig = sg_virt(sg);

		while (sg_remaining) {
			if (!std || std->len == max_std_len) {
				std = qset_new_std(whc, qset, urb, mem_flags);
				if (std == NULL)
					return -ENOMEM;
				std->bounce_buf = kmalloc(max_std_len, mem_flags);
				if (std->bounce_buf == NULL)
					return -ENOMEM;
				std->bounce_sg = sg;
				std->bounce_offset = orig - sg_virt(sg);
				bounce = std->bounce_buf;
				ntds++;
			}

			len = min(sg_remaining, max_std_len - std->len);

			if (is_out)
				memcpy(bounce, orig, len);

			std->len += len;
			std->ntds_remaining = -1; /* filled in later */

			bounce += len;
			orig += len;
			sg_remaining -= len;
			remaining -= len;
		}
	}

	/*
	 * For each of the new sTDs, map the bounce buffers, create
	 * page lists (if necessary), and fill in std->ntds_remaining.
	 */
	list_for_each_entry(std, &qset->stds, list_node) {
		if (std->ntds_remaining != -1)
			continue;

		std->dma_addr = dma_map_single(&whc->umc->dev, std->bounce_buf, std->len,
					       is_out ? DMA_TO_DEVICE : DMA_FROM_DEVICE);
		if (dma_mapping_error(&whc->umc->dev, std->dma_addr))
			return -EFAULT;

		if (qset_fill_page_list(whc, std, mem_flags) < 0)
			return -ENOMEM;

		std->ntds_remaining = ntds--;
	}

	return 0;
}

/**
 * qset_add_urb - add an urb to the qset's queue.
 *
 * The URB is chopped into sTDs, one for each qTD that will required.
 * At least one qTD (and sTD) is required even if the transfer has no
 * data (e.g., for some control transfers).
 */
int qset_add_urb(struct whc *whc, struct whc_qset *qset, struct urb *urb,
	gfp_t mem_flags)
{
	struct whc_urb *wurb;
	int remaining = urb->transfer_buffer_length;
	u64 transfer_dma = urb->transfer_dma;
	int ntds_remaining;
	int ret;

	wurb = kzalloc(sizeof(struct whc_urb), mem_flags);
	if (wurb == NULL)
		goto err_no_mem;
	urb->hcpriv = wurb;
	wurb->qset = qset;
	wurb->urb = urb;
	INIT_WORK(&wurb->dequeue_work, urb_dequeue_work);

	if (urb->num_sgs) {
		ret = qset_add_urb_sg(whc, qset, urb, mem_flags);
		if (ret == -EINVAL) {
			qset_free_stds(qset, urb);
			ret = qset_add_urb_sg_linearize(whc, qset, urb, mem_flags);
		}
		if (ret < 0)
			goto err_no_mem;
		return 0;
	}

	ntds_remaining = DIV_ROUND_UP(remaining, QTD_MAX_XFER_SIZE);
	if (ntds_remaining == 0)
		ntds_remaining = 1;

	while (ntds_remaining) {
		struct whc_std *std;
		size_t std_len;

		std_len = remaining;
		if (std_len > QTD_MAX_XFER_SIZE)
			std_len = QTD_MAX_XFER_SIZE;

		std = qset_new_std(whc, qset, urb, mem_flags);
		if (std == NULL)
			goto err_no_mem;

		std->dma_addr = transfer_dma;
		std->len = std_len;
		std->ntds_remaining = ntds_remaining;

		if (qset_fill_page_list(whc, std, mem_flags) < 0)
			goto err_no_mem;

		ntds_remaining--;
		remaining -= std_len;
		transfer_dma += std_len;
	}

	return 0;

err_no_mem:
	qset_free_stds(qset, urb);
	return -ENOMEM;
}

/**
 * qset_remove_urb - remove an URB from the urb queue.
 *
 * The URB is returned to the USB subsystem.
 */
void qset_remove_urb(struct whc *whc, struct whc_qset *qset,
			    struct urb *urb, int status)
{
	struct wusbhc *wusbhc = &whc->wusbhc;
	struct whc_urb *wurb = urb->hcpriv;

	usb_hcd_unlink_urb_from_ep(&wusbhc->usb_hcd, urb);
	/* Drop the lock as urb->complete() may enqueue another urb. */
	spin_unlock(&whc->lock);
	wusbhc_giveback_urb(wusbhc, urb, status);
	spin_lock(&whc->lock);

	kfree(wurb);
}

/**
 * get_urb_status_from_qtd - get the completed urb status from qTD status
 * @urb:    completed urb
 * @status: qTD status
 */
static int get_urb_status_from_qtd(struct urb *urb, u32 status)
{
	if (status & QTD_STS_HALTED) {
		if (status & QTD_STS_DBE)
			return usb_pipein(urb->pipe) ? -ENOSR : -ECOMM;
		else if (status & QTD_STS_BABBLE)
			return -EOVERFLOW;
		else if (status & QTD_STS_RCE)
			return -ETIME;
		return -EPIPE;
	}
	if (usb_pipein(urb->pipe)
	    && (urb->transfer_flags & URB_SHORT_NOT_OK)
	    && urb->actual_length < urb->transfer_buffer_length)
		return -EREMOTEIO;
	return 0;
}

/**
 * process_inactive_qtd - process an inactive (but not halted) qTD.
 *
 * Update the urb with the transfer bytes from the qTD, if the urb is
 * completely transferred or (in the case of an IN only) the LPF is
 * set, then the transfer is complete and the urb should be returned
 * to the system.
 */
void process_inactive_qtd(struct whc *whc, struct whc_qset *qset,
				 struct whc_qtd *qtd)
{
	struct whc_std *std = list_first_entry(&qset->stds, struct whc_std, list_node);
	struct urb *urb = std->urb;
	uint32_t status;
	bool complete;

	status = le32_to_cpu(qtd->status);

	urb->actual_length += std->len - QTD_STS_TO_LEN(status);

	if (usb_pipein(urb->pipe) && (status & QTD_STS_LAST_PKT))
		complete = true;
	else
		complete = whc_std_last(std);

	qset_remove_qtd(whc, qset);
	qset_free_std(whc, std);

	/*
	 * Transfers for this URB are complete?  Then return it to the
	 * USB subsystem.
	 */
	if (complete) {
		qset_remove_qtds(whc, qset, urb);
		qset_remove_urb(whc, qset, urb, get_urb_status_from_qtd(urb, status));

		/*
		 * If iAlt isn't valid then the hardware didn't
		 * advance iCur. Adjust the start and end pointers to
		 * match iCur.
		 */
		if (!(status & QTD_STS_IALT_VALID))
			qset->td_start = qset->td_end
				= QH_STATUS_TO_ICUR(le16_to_cpu(qset->qh.status));
		qset->pause_after_urb = NULL;
	}
}

/**
 * process_halted_qtd - process a qset with a halted qtd
 *
 * Remove all the qTDs for the failed URB and return the failed URB to
 * the USB subsystem.  Then remove all other qTDs so the qset can be
 * removed.
 *
 * FIXME: this is the point where rate adaptation can be done.  If a
 * transfer failed because it exceeded the maximum number of retries
 * then it could be reactivated with a slower rate without having to
 * remove the qset.
 */
void process_halted_qtd(struct whc *whc, struct whc_qset *qset,
			       struct whc_qtd *qtd)
{
	struct whc_std *std = list_first_entry(&qset->stds, struct whc_std, list_node);
	struct urb *urb = std->urb;
	int urb_status;

	urb_status = get_urb_status_from_qtd(urb, le32_to_cpu(qtd->status));

	qset_remove_qtds(whc, qset, urb);
	qset_remove_urb(whc, qset, urb, urb_status);

	list_for_each_entry(std, &qset->stds, list_node) {
		if (qset->ntds == 0)
			break;
		qset_remove_qtd(whc, qset);
		std->qtd = NULL;
	}

	qset->remove = 1;
}

void qset_free(struct whc *whc, struct whc_qset *qset)
{
	dma_pool_free(whc->qset_pool, qset, qset->qset_dma);
}

/**
 * qset_delete - wait for a qset to be unused, then free it.
 */
void qset_delete(struct whc *whc, struct whc_qset *qset)
{
	wait_for_completion(&qset->remove_complete);
	qset_free(whc, qset);
}