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qemu-patch-raspberry4/hw/usb/core.c
Hans de Goede be41efde3c usb: Don't allow USB_RET_ASYNC for interrupt packets 
It is tempting to use USB_RET_ASYNC for interrupt packets, rather then the
current NAK + polling approach, but this causes issues for migration, as
an async completed packet will not getting written back to guest memory until
the next poll time, and if a migration happens in between it will get lost!

Make an exception for host devices, because:
1) host-linux actually uses async completion for interrupt endpoints
2) host devices don't migrate anyways

Ideally we would convert host-linux.c to handle (input) interrupt endpoints in
a buffered manner like it does for isoc endpoints, keeping multiple urbs
submitted to ensure the devices timing requirements are met, as well as making
its interrupt ep handling the same as other usb-devices.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
2012-12-04 14:41:54 +01:00

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/*
* QEMU USB emulation
*
* Copyright (c) 2005 Fabrice Bellard
*
* 2008 Generic packet handler rewrite by Max Krasnyansky
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#include "qemu-common.h"
#include "hw/usb.h"
#include "iov.h"
#include "trace.h"
void usb_attach(USBPort *port)
{
USBDevice *dev = port->dev;
assert(dev != NULL);
assert(dev->attached);
assert(dev->state == USB_STATE_NOTATTACHED);
port->ops->attach(port);
dev->state = USB_STATE_ATTACHED;
usb_device_handle_attach(dev);
}
void usb_detach(USBPort *port)
{
USBDevice *dev = port->dev;
assert(dev != NULL);
assert(dev->state != USB_STATE_NOTATTACHED);
port->ops->detach(port);
dev->state = USB_STATE_NOTATTACHED;
}
void usb_port_reset(USBPort *port)
{
USBDevice *dev = port->dev;
assert(dev != NULL);
usb_detach(port);
usb_attach(port);
usb_device_reset(dev);
}
void usb_device_reset(USBDevice *dev)
{
if (dev == NULL || !dev->attached) {
return;
}
dev->remote_wakeup = 0;
dev->addr = 0;
dev->state = USB_STATE_DEFAULT;
usb_device_handle_reset(dev);
}
void usb_wakeup(USBEndpoint *ep)
{
USBDevice *dev = ep->dev;
USBBus *bus = usb_bus_from_device(dev);
if (dev->remote_wakeup && dev->port && dev->port->ops->wakeup) {
dev->port->ops->wakeup(dev->port);
}
if (bus->ops->wakeup_endpoint) {
bus->ops->wakeup_endpoint(bus, ep);
}
}
/**********************/
/* generic USB device helpers (you are not forced to use them when
writing your USB device driver, but they help handling the
protocol)
*/
#define SETUP_STATE_IDLE 0
#define SETUP_STATE_SETUP 1
#define SETUP_STATE_DATA 2
#define SETUP_STATE_ACK 3
#define SETUP_STATE_PARAM 4
static void do_token_setup(USBDevice *s, USBPacket *p)
{
int request, value, index;
if (p->iov.size != 8) {
p->status = USB_RET_STALL;
return;
}
usb_packet_copy(p, s->setup_buf, p->iov.size);
p->actual_length = 0;
s->setup_len = (s->setup_buf[7] << 8) | s->setup_buf[6];
s->setup_index = 0;
request = (s->setup_buf[0] << 8) | s->setup_buf[1];
value = (s->setup_buf[3] << 8) | s->setup_buf[2];
index = (s->setup_buf[5] << 8) | s->setup_buf[4];
if (s->setup_buf[0] & USB_DIR_IN) {
usb_device_handle_control(s, p, request, value, index,
s->setup_len, s->data_buf);
if (p->status == USB_RET_ASYNC) {
s->setup_state = SETUP_STATE_SETUP;
}
if (p->status != USB_RET_SUCCESS) {
return;
}
if (p->actual_length < s->setup_len) {
s->setup_len = p->actual_length;
}
s->setup_state = SETUP_STATE_DATA;
} else {
if (s->setup_len > sizeof(s->data_buf)) {
fprintf(stderr,
"usb_generic_handle_packet: ctrl buffer too small (%d > %zu)\n",
s->setup_len, sizeof(s->data_buf));
p->status = USB_RET_STALL;
return;
}
if (s->setup_len == 0)
s->setup_state = SETUP_STATE_ACK;
else
s->setup_state = SETUP_STATE_DATA;
}
p->actual_length = 8;
}
static void do_token_in(USBDevice *s, USBPacket *p)
{
int request, value, index;
assert(p->ep->nr == 0);
request = (s->setup_buf[0] << 8) | s->setup_buf[1];
value = (s->setup_buf[3] << 8) | s->setup_buf[2];
index = (s->setup_buf[5] << 8) | s->setup_buf[4];
switch(s->setup_state) {
case SETUP_STATE_ACK:
if (!(s->setup_buf[0] & USB_DIR_IN)) {
usb_device_handle_control(s, p, request, value, index,
s->setup_len, s->data_buf);
if (p->status == USB_RET_ASYNC) {
return;
}
s->setup_state = SETUP_STATE_IDLE;
p->actual_length = 0;
}
break;
case SETUP_STATE_DATA:
if (s->setup_buf[0] & USB_DIR_IN) {
int len = s->setup_len - s->setup_index;
if (len > p->iov.size) {
len = p->iov.size;
}
usb_packet_copy(p, s->data_buf + s->setup_index, len);
s->setup_index += len;
if (s->setup_index >= s->setup_len) {
s->setup_state = SETUP_STATE_ACK;
}
return;
}
s->setup_state = SETUP_STATE_IDLE;
p->status = USB_RET_STALL;
break;
default:
p->status = USB_RET_STALL;
}
}
static void do_token_out(USBDevice *s, USBPacket *p)
{
assert(p->ep->nr == 0);
switch(s->setup_state) {
case SETUP_STATE_ACK:
if (s->setup_buf[0] & USB_DIR_IN) {
s->setup_state = SETUP_STATE_IDLE;
/* transfer OK */
} else {
/* ignore additional output */
}
break;
case SETUP_STATE_DATA:
if (!(s->setup_buf[0] & USB_DIR_IN)) {
int len = s->setup_len - s->setup_index;
if (len > p->iov.size) {
len = p->iov.size;
}
usb_packet_copy(p, s->data_buf + s->setup_index, len);
s->setup_index += len;
if (s->setup_index >= s->setup_len) {
s->setup_state = SETUP_STATE_ACK;
}
return;
}
s->setup_state = SETUP_STATE_IDLE;
p->status = USB_RET_STALL;
break;
default:
p->status = USB_RET_STALL;
}
}
static void do_parameter(USBDevice *s, USBPacket *p)
{
int i, request, value, index;
for (i = 0; i < 8; i++) {
s->setup_buf[i] = p->parameter >> (i*8);
}
s->setup_state = SETUP_STATE_PARAM;
s->setup_len = (s->setup_buf[7] << 8) | s->setup_buf[6];
s->setup_index = 0;
request = (s->setup_buf[0] << 8) | s->setup_buf[1];
value = (s->setup_buf[3] << 8) | s->setup_buf[2];
index = (s->setup_buf[5] << 8) | s->setup_buf[4];
if (s->setup_len > sizeof(s->data_buf)) {
fprintf(stderr,
"usb_generic_handle_packet: ctrl buffer too small (%d > %zu)\n",
s->setup_len, sizeof(s->data_buf));
p->status = USB_RET_STALL;
return;
}
if (p->pid == USB_TOKEN_OUT) {
usb_packet_copy(p, s->data_buf, s->setup_len);
}
usb_device_handle_control(s, p, request, value, index,
s->setup_len, s->data_buf);
if (p->status == USB_RET_ASYNC) {
return;
}
if (p->actual_length < s->setup_len) {
s->setup_len = p->actual_length;
}
if (p->pid == USB_TOKEN_IN) {
p->actual_length = 0;
usb_packet_copy(p, s->data_buf, s->setup_len);
}
}
/* ctrl complete function for devices which use usb_generic_handle_packet and
may return USB_RET_ASYNC from their handle_control callback. Device code
which does this *must* call this function instead of the normal
usb_packet_complete to complete their async control packets. */
void usb_generic_async_ctrl_complete(USBDevice *s, USBPacket *p)
{
if (p->status < 0) {
s->setup_state = SETUP_STATE_IDLE;
}
switch (s->setup_state) {
case SETUP_STATE_SETUP:
if (p->actual_length < s->setup_len) {
s->setup_len = p->actual_length;
}
s->setup_state = SETUP_STATE_DATA;
p->actual_length = 8;
break;
case SETUP_STATE_ACK:
s->setup_state = SETUP_STATE_IDLE;
p->actual_length = 0;
break;
case SETUP_STATE_PARAM:
if (p->actual_length < s->setup_len) {
s->setup_len = p->actual_length;
}
if (p->pid == USB_TOKEN_IN) {
p->actual_length = 0;
usb_packet_copy(p, s->data_buf, s->setup_len);
}
break;
default:
break;
}
usb_packet_complete(s, p);
}
/* XXX: fix overflow */
int set_usb_string(uint8_t *buf, const char *str)
{
int len, i;
uint8_t *q;
q = buf;
len = strlen(str);
*q++ = 2 * len + 2;
*q++ = 3;
for(i = 0; i < len; i++) {
*q++ = str[i];
*q++ = 0;
}
return q - buf;
}
USBDevice *usb_find_device(USBPort *port, uint8_t addr)
{
USBDevice *dev = port->dev;
if (dev == NULL || !dev->attached || dev->state != USB_STATE_DEFAULT) {
return NULL;
}
if (dev->addr == addr) {
return dev;
}
return usb_device_find_device(dev, addr);
}
static void usb_process_one(USBPacket *p)
{
USBDevice *dev = p->ep->dev;
/*
* Handlers expect status to be initialized to USB_RET_SUCCESS, but it
* can be USB_RET_NAK here from a previous usb_process_one() call,
* or USB_RET_ASYNC from going through usb_queue_one().
*/
p->status = USB_RET_SUCCESS;
if (p->ep->nr == 0) {
/* control pipe */
if (p->parameter) {
do_parameter(dev, p);
return;
}
switch (p->pid) {
case USB_TOKEN_SETUP:
do_token_setup(dev, p);
break;
case USB_TOKEN_IN:
do_token_in(dev, p);
break;
case USB_TOKEN_OUT:
do_token_out(dev, p);
break;
default:
p->status = USB_RET_STALL;
}
} else {
/* data pipe */
usb_device_handle_data(dev, p);
}
}
static void usb_queue_one(USBPacket *p)
{
usb_packet_set_state(p, USB_PACKET_QUEUED);
QTAILQ_INSERT_TAIL(&p->ep->queue, p, queue);
p->status = USB_RET_ASYNC;
}
/* Hand over a packet to a device for processing. p->status ==
USB_RET_ASYNC indicates the processing isn't finished yet, the
driver will call usb_packet_complete() when done processing it. */
void usb_handle_packet(USBDevice *dev, USBPacket *p)
{
if (dev == NULL) {
p->status = USB_RET_NODEV;
return;
}
assert(dev == p->ep->dev);
assert(dev->state == USB_STATE_DEFAULT);
usb_packet_check_state(p, USB_PACKET_SETUP);
assert(p->ep != NULL);
/* Submitting a new packet clears halt */
if (p->ep->halted) {
assert(QTAILQ_EMPTY(&p->ep->queue));
p->ep->halted = false;
}
if (QTAILQ_EMPTY(&p->ep->queue) || p->ep->pipeline) {
usb_process_one(p);
if (p->status == USB_RET_ASYNC) {
/* hcd drivers cannot handle async for isoc */
assert(p->ep->type != USB_ENDPOINT_XFER_ISOC);
/* using async for interrupt packets breaks migration */
assert(p->ep->type != USB_ENDPOINT_XFER_INT ||
(dev->flags & USB_DEV_FLAG_IS_HOST));
usb_packet_set_state(p, USB_PACKET_ASYNC);
QTAILQ_INSERT_TAIL(&p->ep->queue, p, queue);
} else if (p->status == USB_RET_ADD_TO_QUEUE) {
usb_queue_one(p);
} else {
/*
* When pipelining is enabled usb-devices must always return async,
* otherwise packets can complete out of order!
*/
assert(!p->ep->pipeline || QTAILQ_EMPTY(&p->ep->queue));
if (p->status != USB_RET_NAK) {
usb_packet_set_state(p, USB_PACKET_COMPLETE);
}
}
} else {
usb_queue_one(p);
}
}
void usb_packet_complete_one(USBDevice *dev, USBPacket *p)
{
USBEndpoint *ep = p->ep;
assert(QTAILQ_FIRST(&ep->queue) == p);
assert(p->status != USB_RET_ASYNC && p->status != USB_RET_NAK);
if (p->status != USB_RET_SUCCESS ||
(p->short_not_ok && (p->actual_length < p->iov.size))) {
ep->halted = true;
}
usb_packet_set_state(p, USB_PACKET_COMPLETE);
QTAILQ_REMOVE(&ep->queue, p, queue);
dev->port->ops->complete(dev->port, p);
}
/* Notify the controller that an async packet is complete. This should only
be called for packets previously deferred by returning USB_RET_ASYNC from
handle_packet. */
void usb_packet_complete(USBDevice *dev, USBPacket *p)
{
USBEndpoint *ep = p->ep;
usb_packet_check_state(p, USB_PACKET_ASYNC);
usb_packet_complete_one(dev, p);
while (!QTAILQ_EMPTY(&ep->queue)) {
p = QTAILQ_FIRST(&ep->queue);
if (ep->halted) {
/* Empty the queue on a halt */
p->status = USB_RET_REMOVE_FROM_QUEUE;
dev->port->ops->complete(dev->port, p);
continue;
}
if (p->state == USB_PACKET_ASYNC) {
break;
}
usb_packet_check_state(p, USB_PACKET_QUEUED);
usb_process_one(p);
if (p->status == USB_RET_ASYNC) {
usb_packet_set_state(p, USB_PACKET_ASYNC);
break;
}
usb_packet_complete_one(ep->dev, p);
}
}
/* Cancel an active packet. The packed must have been deferred by
returning USB_RET_ASYNC from handle_packet, and not yet
completed. */
void usb_cancel_packet(USBPacket * p)
{
bool callback = (p->state == USB_PACKET_ASYNC);
assert(usb_packet_is_inflight(p));
usb_packet_set_state(p, USB_PACKET_CANCELED);
QTAILQ_REMOVE(&p->ep->queue, p, queue);
if (callback) {
usb_device_cancel_packet(p->ep->dev, p);
}
}
void usb_packet_init(USBPacket *p)
{
qemu_iovec_init(&p->iov, 1);
}
static const char *usb_packet_state_name(USBPacketState state)
{
static const char *name[] = {
[USB_PACKET_UNDEFINED] = "undef",
[USB_PACKET_SETUP] = "setup",
[USB_PACKET_QUEUED] = "queued",
[USB_PACKET_ASYNC] = "async",
[USB_PACKET_COMPLETE] = "complete",
[USB_PACKET_CANCELED] = "canceled",
};
if (state < ARRAY_SIZE(name)) {
return name[state];
}
return "INVALID";
}
void usb_packet_check_state(USBPacket *p, USBPacketState expected)
{
USBDevice *dev;
USBBus *bus;
if (p->state == expected) {
return;
}
dev = p->ep->dev;
bus = usb_bus_from_device(dev);
trace_usb_packet_state_fault(bus->busnr, dev->port->path, p->ep->nr, p,
usb_packet_state_name(p->state),
usb_packet_state_name(expected));
assert(!"usb packet state check failed");
}
void usb_packet_set_state(USBPacket *p, USBPacketState state)
{
if (p->ep) {
USBDevice *dev = p->ep->dev;
USBBus *bus = usb_bus_from_device(dev);
trace_usb_packet_state_change(bus->busnr, dev->port->path, p->ep->nr, p,
usb_packet_state_name(p->state),
usb_packet_state_name(state));
} else {
trace_usb_packet_state_change(-1, "", -1, p,
usb_packet_state_name(p->state),
usb_packet_state_name(state));
}
p->state = state;
}
void usb_packet_setup(USBPacket *p, int pid, USBEndpoint *ep, uint64_t id,
bool short_not_ok, bool int_req)
{
assert(!usb_packet_is_inflight(p));
assert(p->iov.iov != NULL);
p->id = id;
p->pid = pid;
p->ep = ep;
p->status = USB_RET_SUCCESS;
p->actual_length = 0;
p->parameter = 0;
p->short_not_ok = short_not_ok;
p->int_req = int_req;
p->combined = NULL;
qemu_iovec_reset(&p->iov);
usb_packet_set_state(p, USB_PACKET_SETUP);
}
void usb_packet_addbuf(USBPacket *p, void *ptr, size_t len)
{
qemu_iovec_add(&p->iov, ptr, len);
}
void usb_packet_copy(USBPacket *p, void *ptr, size_t bytes)
{
assert(p->actual_length >= 0);
assert(p->actual_length + bytes <= p->iov.size);
switch (p->pid) {
case USB_TOKEN_SETUP:
case USB_TOKEN_OUT:
iov_to_buf(p->iov.iov, p->iov.niov, p->actual_length, ptr, bytes);
break;
case USB_TOKEN_IN:
iov_from_buf(p->iov.iov, p->iov.niov, p->actual_length, ptr, bytes);
break;
default:
fprintf(stderr, "%s: invalid pid: %x\n", __func__, p->pid);
abort();
}
p->actual_length += bytes;
}
void usb_packet_skip(USBPacket *p, size_t bytes)
{
assert(p->actual_length >= 0);
assert(p->actual_length + bytes <= p->iov.size);
if (p->pid == USB_TOKEN_IN) {
iov_memset(p->iov.iov, p->iov.niov, p->actual_length, 0, bytes);
}
p->actual_length += bytes;
}
void usb_packet_cleanup(USBPacket *p)
{
assert(!usb_packet_is_inflight(p));
qemu_iovec_destroy(&p->iov);
}
void usb_ep_reset(USBDevice *dev)
{
int ep;
dev->ep_ctl.nr = 0;
dev->ep_ctl.type = USB_ENDPOINT_XFER_CONTROL;
dev->ep_ctl.ifnum = 0;
dev->ep_ctl.dev = dev;
dev->ep_ctl.pipeline = false;
for (ep = 0; ep < USB_MAX_ENDPOINTS; ep++) {
dev->ep_in[ep].nr = ep + 1;
dev->ep_out[ep].nr = ep + 1;
dev->ep_in[ep].pid = USB_TOKEN_IN;
dev->ep_out[ep].pid = USB_TOKEN_OUT;
dev->ep_in[ep].type = USB_ENDPOINT_XFER_INVALID;
dev->ep_out[ep].type = USB_ENDPOINT_XFER_INVALID;
dev->ep_in[ep].ifnum = USB_INTERFACE_INVALID;
dev->ep_out[ep].ifnum = USB_INTERFACE_INVALID;
dev->ep_in[ep].dev = dev;
dev->ep_out[ep].dev = dev;
dev->ep_in[ep].pipeline = false;
dev->ep_out[ep].pipeline = false;
}
}
void usb_ep_init(USBDevice *dev)
{
int ep;
usb_ep_reset(dev);
QTAILQ_INIT(&dev->ep_ctl.queue);
for (ep = 0; ep < USB_MAX_ENDPOINTS; ep++) {
QTAILQ_INIT(&dev->ep_in[ep].queue);
QTAILQ_INIT(&dev->ep_out[ep].queue);
}
}
void usb_ep_dump(USBDevice *dev)
{
static const char *tname[] = {
[USB_ENDPOINT_XFER_CONTROL] = "control",
[USB_ENDPOINT_XFER_ISOC] = "isoc",
[USB_ENDPOINT_XFER_BULK] = "bulk",
[USB_ENDPOINT_XFER_INT] = "int",
};
int ifnum, ep, first;
fprintf(stderr, "Device \"%s\", config %d\n",
dev->product_desc, dev->configuration);
for (ifnum = 0; ifnum < 16; ifnum++) {
first = 1;
for (ep = 0; ep < USB_MAX_ENDPOINTS; ep++) {
if (dev->ep_in[ep].type != USB_ENDPOINT_XFER_INVALID &&
dev->ep_in[ep].ifnum == ifnum) {
if (first) {
first = 0;
fprintf(stderr, " Interface %d, alternative %d\n",
ifnum, dev->altsetting[ifnum]);
}
fprintf(stderr, " Endpoint %d, IN, %s, %d max\n", ep,
tname[dev->ep_in[ep].type],
dev->ep_in[ep].max_packet_size);
}
if (dev->ep_out[ep].type != USB_ENDPOINT_XFER_INVALID &&
dev->ep_out[ep].ifnum == ifnum) {
if (first) {
first = 0;
fprintf(stderr, " Interface %d, alternative %d\n",
ifnum, dev->altsetting[ifnum]);
}
fprintf(stderr, " Endpoint %d, OUT, %s, %d max\n", ep,
tname[dev->ep_out[ep].type],
dev->ep_out[ep].max_packet_size);
}
}
}
fprintf(stderr, "--\n");
}
struct USBEndpoint *usb_ep_get(USBDevice *dev, int pid, int ep)
{
struct USBEndpoint *eps;
if (dev == NULL) {
return NULL;
}
eps = (pid == USB_TOKEN_IN) ? dev->ep_in : dev->ep_out;
if (ep == 0) {
return &dev->ep_ctl;
}
assert(pid == USB_TOKEN_IN || pid == USB_TOKEN_OUT);
assert(ep > 0 && ep <= USB_MAX_ENDPOINTS);
return eps + ep - 1;
}
uint8_t usb_ep_get_type(USBDevice *dev, int pid, int ep)
{
struct USBEndpoint *uep = usb_ep_get(dev, pid, ep);
return uep->type;
}
void usb_ep_set_type(USBDevice *dev, int pid, int ep, uint8_t type)
{
struct USBEndpoint *uep = usb_ep_get(dev, pid, ep);
uep->type = type;
}
uint8_t usb_ep_get_ifnum(USBDevice *dev, int pid, int ep)
{
struct USBEndpoint *uep = usb_ep_get(dev, pid, ep);
return uep->ifnum;
}
void usb_ep_set_ifnum(USBDevice *dev, int pid, int ep, uint8_t ifnum)
{
struct USBEndpoint *uep = usb_ep_get(dev, pid, ep);
uep->ifnum = ifnum;
}
void usb_ep_set_max_packet_size(USBDevice *dev, int pid, int ep,
uint16_t raw)
{
struct USBEndpoint *uep = usb_ep_get(dev, pid, ep);
int size, microframes;
size = raw & 0x7ff;
switch ((raw >> 11) & 3) {
case 1:
microframes = 2;
break;
case 2:
microframes = 3;
break;
default:
microframes = 1;
break;
}
uep->max_packet_size = size * microframes;
}
int usb_ep_get_max_packet_size(USBDevice *dev, int pid, int ep)
{
struct USBEndpoint *uep = usb_ep_get(dev, pid, ep);
return uep->max_packet_size;
}
void usb_ep_set_pipeline(USBDevice *dev, int pid, int ep, bool enabled)
{
struct USBEndpoint *uep = usb_ep_get(dev, pid, ep);
uep->pipeline = enabled;
}
USBPacket *usb_ep_find_packet_by_id(USBDevice *dev, int pid, int ep,
uint64_t id)
{
struct USBEndpoint *uep = usb_ep_get(dev, pid, ep);
USBPacket *p;
while ((p = QTAILQ_FIRST(&uep->queue)) != NULL) {
if (p->id == id) {
return p;
}
}
return NULL;
}
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