![Alan Stern](/assets/img/avatar_default.png)
This patch (as936) updates the kerneldoc for usb_unlink_urb. The explanation of how endpoint queues are meant to work is now clearer and in better agreement with reality. Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
590 lines
20 KiB
C
590 lines
20 KiB
C
#include <linux/module.h>
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#include <linux/string.h>
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#include <linux/bitops.h>
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#include <linux/slab.h>
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#include <linux/init.h>
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#include <linux/usb.h>
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#include <linux/wait.h>
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#include "hcd.h"
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#define to_urb(d) container_of(d, struct urb, kref)
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static void urb_destroy(struct kref *kref)
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{
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struct urb *urb = to_urb(kref);
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if (urb->transfer_flags & URB_FREE_BUFFER)
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kfree(urb->transfer_buffer);
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kfree(urb);
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}
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/**
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* usb_init_urb - initializes a urb so that it can be used by a USB driver
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* @urb: pointer to the urb to initialize
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*
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* Initializes a urb so that the USB subsystem can use it properly.
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*
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* If a urb is created with a call to usb_alloc_urb() it is not
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* necessary to call this function. Only use this if you allocate the
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* space for a struct urb on your own. If you call this function, be
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* careful when freeing the memory for your urb that it is no longer in
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* use by the USB core.
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*
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* Only use this function if you _really_ understand what you are doing.
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*/
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void usb_init_urb(struct urb *urb)
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{
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if (urb) {
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memset(urb, 0, sizeof(*urb));
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kref_init(&urb->kref);
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spin_lock_init(&urb->lock);
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INIT_LIST_HEAD(&urb->anchor_list);
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}
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}
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/**
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* usb_alloc_urb - creates a new urb for a USB driver to use
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* @iso_packets: number of iso packets for this urb
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* @mem_flags: the type of memory to allocate, see kmalloc() for a list of
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* valid options for this.
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*
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* Creates an urb for the USB driver to use, initializes a few internal
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* structures, incrementes the usage counter, and returns a pointer to it.
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*
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* If no memory is available, NULL is returned.
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*
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* If the driver want to use this urb for interrupt, control, or bulk
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* endpoints, pass '0' as the number of iso packets.
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*
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* The driver must call usb_free_urb() when it is finished with the urb.
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*/
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struct urb *usb_alloc_urb(int iso_packets, gfp_t mem_flags)
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{
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struct urb *urb;
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urb = kmalloc(sizeof(struct urb) +
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iso_packets * sizeof(struct usb_iso_packet_descriptor),
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mem_flags);
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if (!urb) {
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err("alloc_urb: kmalloc failed");
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return NULL;
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}
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usb_init_urb(urb);
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return urb;
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}
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/**
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* usb_free_urb - frees the memory used by a urb when all users of it are finished
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* @urb: pointer to the urb to free, may be NULL
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*
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* Must be called when a user of a urb is finished with it. When the last user
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* of the urb calls this function, the memory of the urb is freed.
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*
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* Note: The transfer buffer associated with the urb is not freed, that must be
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* done elsewhere.
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*/
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void usb_free_urb(struct urb *urb)
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{
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if (urb)
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kref_put(&urb->kref, urb_destroy);
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}
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/**
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* usb_get_urb - increments the reference count of the urb
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* @urb: pointer to the urb to modify, may be NULL
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*
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* This must be called whenever a urb is transferred from a device driver to a
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* host controller driver. This allows proper reference counting to happen
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* for urbs.
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*
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* A pointer to the urb with the incremented reference counter is returned.
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*/
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struct urb * usb_get_urb(struct urb *urb)
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{
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if (urb)
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kref_get(&urb->kref);
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return urb;
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}
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/**
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* usb_anchor_urb - anchors an URB while it is processed
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* @urb: pointer to the urb to anchor
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* @anchor: pointer to the anchor
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*
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* This can be called to have access to URBs which are to be executed
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* without bothering to track them
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*/
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void usb_anchor_urb(struct urb *urb, struct usb_anchor *anchor)
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{
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unsigned long flags;
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spin_lock_irqsave(&anchor->lock, flags);
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usb_get_urb(urb);
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list_add_tail(&urb->anchor_list, &anchor->urb_list);
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urb->anchor = anchor;
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spin_unlock_irqrestore(&anchor->lock, flags);
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}
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EXPORT_SYMBOL_GPL(usb_anchor_urb);
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/**
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* usb_unanchor_urb - unanchors an URB
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* @urb: pointer to the urb to anchor
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*
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* Call this to stop the system keeping track of this URB
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*/
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void usb_unanchor_urb(struct urb *urb)
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{
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unsigned long flags;
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struct usb_anchor *anchor;
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if (!urb)
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return;
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anchor = urb->anchor;
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if (!anchor)
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return;
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spin_lock_irqsave(&anchor->lock, flags);
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if (unlikely(anchor != urb->anchor)) {
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/* we've lost the race to another thread */
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spin_unlock_irqrestore(&anchor->lock, flags);
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return;
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}
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urb->anchor = NULL;
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list_del(&urb->anchor_list);
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spin_unlock_irqrestore(&anchor->lock, flags);
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usb_put_urb(urb);
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if (list_empty(&anchor->urb_list))
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wake_up(&anchor->wait);
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}
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EXPORT_SYMBOL_GPL(usb_unanchor_urb);
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/*-------------------------------------------------------------------*/
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/**
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* usb_submit_urb - issue an asynchronous transfer request for an endpoint
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* @urb: pointer to the urb describing the request
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* @mem_flags: the type of memory to allocate, see kmalloc() for a list
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* of valid options for this.
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*
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* This submits a transfer request, and transfers control of the URB
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* describing that request to the USB subsystem. Request completion will
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* be indicated later, asynchronously, by calling the completion handler.
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* The three types of completion are success, error, and unlink
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* (a software-induced fault, also called "request cancellation").
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*
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* URBs may be submitted in interrupt context.
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*
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* The caller must have correctly initialized the URB before submitting
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* it. Functions such as usb_fill_bulk_urb() and usb_fill_control_urb() are
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* available to ensure that most fields are correctly initialized, for
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* the particular kind of transfer, although they will not initialize
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* any transfer flags.
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*
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* Successful submissions return 0; otherwise this routine returns a
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* negative error number. If the submission is successful, the complete()
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* callback from the URB will be called exactly once, when the USB core and
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* Host Controller Driver (HCD) are finished with the URB. When the completion
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* function is called, control of the URB is returned to the device
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* driver which issued the request. The completion handler may then
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* immediately free or reuse that URB.
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*
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* With few exceptions, USB device drivers should never access URB fields
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* provided by usbcore or the HCD until its complete() is called.
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* The exceptions relate to periodic transfer scheduling. For both
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* interrupt and isochronous urbs, as part of successful URB submission
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* urb->interval is modified to reflect the actual transfer period used
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* (normally some power of two units). And for isochronous urbs,
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* urb->start_frame is modified to reflect when the URB's transfers were
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* scheduled to start. Not all isochronous transfer scheduling policies
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* will work, but most host controller drivers should easily handle ISO
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* queues going from now until 10-200 msec into the future.
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*
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* For control endpoints, the synchronous usb_control_msg() call is
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* often used (in non-interrupt context) instead of this call.
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* That is often used through convenience wrappers, for the requests
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* that are standardized in the USB 2.0 specification. For bulk
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* endpoints, a synchronous usb_bulk_msg() call is available.
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*
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* Request Queuing:
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*
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* URBs may be submitted to endpoints before previous ones complete, to
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* minimize the impact of interrupt latencies and system overhead on data
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* throughput. With that queuing policy, an endpoint's queue would never
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* be empty. This is required for continuous isochronous data streams,
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* and may also be required for some kinds of interrupt transfers. Such
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* queuing also maximizes bandwidth utilization by letting USB controllers
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* start work on later requests before driver software has finished the
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* completion processing for earlier (successful) requests.
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*
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* As of Linux 2.6, all USB endpoint transfer queues support depths greater
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* than one. This was previously a HCD-specific behavior, except for ISO
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* transfers. Non-isochronous endpoint queues are inactive during cleanup
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* after faults (transfer errors or cancellation).
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*
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* Reserved Bandwidth Transfers:
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*
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* Periodic transfers (interrupt or isochronous) are performed repeatedly,
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* using the interval specified in the urb. Submitting the first urb to
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* the endpoint reserves the bandwidth necessary to make those transfers.
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* If the USB subsystem can't allocate sufficient bandwidth to perform
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* the periodic request, submitting such a periodic request should fail.
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*
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* Device drivers must explicitly request that repetition, by ensuring that
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* some URB is always on the endpoint's queue (except possibly for short
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* periods during completion callacks). When there is no longer an urb
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* queued, the endpoint's bandwidth reservation is canceled. This means
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* drivers can use their completion handlers to ensure they keep bandwidth
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* they need, by reinitializing and resubmitting the just-completed urb
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* until the driver longer needs that periodic bandwidth.
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*
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* Memory Flags:
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*
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* The general rules for how to decide which mem_flags to use
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* are the same as for kmalloc. There are four
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* different possible values; GFP_KERNEL, GFP_NOFS, GFP_NOIO and
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* GFP_ATOMIC.
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*
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* GFP_NOFS is not ever used, as it has not been implemented yet.
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*
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* GFP_ATOMIC is used when
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* (a) you are inside a completion handler, an interrupt, bottom half,
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* tasklet or timer, or
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* (b) you are holding a spinlock or rwlock (does not apply to
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* semaphores), or
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* (c) current->state != TASK_RUNNING, this is the case only after
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* you've changed it.
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*
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* GFP_NOIO is used in the block io path and error handling of storage
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* devices.
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*
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* All other situations use GFP_KERNEL.
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*
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* Some more specific rules for mem_flags can be inferred, such as
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* (1) start_xmit, timeout, and receive methods of network drivers must
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* use GFP_ATOMIC (they are called with a spinlock held);
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* (2) queuecommand methods of scsi drivers must use GFP_ATOMIC (also
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* called with a spinlock held);
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* (3) If you use a kernel thread with a network driver you must use
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* GFP_NOIO, unless (b) or (c) apply;
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* (4) after you have done a down() you can use GFP_KERNEL, unless (b) or (c)
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* apply or your are in a storage driver's block io path;
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* (5) USB probe and disconnect can use GFP_KERNEL unless (b) or (c) apply; and
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* (6) changing firmware on a running storage or net device uses
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* GFP_NOIO, unless b) or c) apply
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*
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*/
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int usb_submit_urb(struct urb *urb, gfp_t mem_flags)
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{
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int pipe, temp, max;
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struct usb_device *dev;
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int is_out;
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if (!urb || urb->hcpriv || !urb->complete)
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return -EINVAL;
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if (!(dev = urb->dev) ||
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(dev->state < USB_STATE_DEFAULT) ||
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(!dev->bus) || (dev->devnum <= 0))
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return -ENODEV;
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if (dev->bus->controller->power.power_state.event != PM_EVENT_ON
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|| dev->state == USB_STATE_SUSPENDED)
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return -EHOSTUNREACH;
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urb->status = -EINPROGRESS;
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urb->actual_length = 0;
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/* Lots of sanity checks, so HCDs can rely on clean data
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* and don't need to duplicate tests
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*/
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pipe = urb->pipe;
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temp = usb_pipetype(pipe);
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is_out = usb_pipeout(pipe);
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if (!usb_pipecontrol(pipe) && dev->state < USB_STATE_CONFIGURED)
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return -ENODEV;
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/* FIXME there should be a sharable lock protecting us against
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* config/altsetting changes and disconnects, kicking in here.
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* (here == before maxpacket, and eventually endpoint type,
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* checks get made.)
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*/
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max = usb_maxpacket(dev, pipe, is_out);
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if (max <= 0) {
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dev_dbg(&dev->dev,
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"bogus endpoint ep%d%s in %s (bad maxpacket %d)\n",
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usb_pipeendpoint(pipe), is_out ? "out" : "in",
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__FUNCTION__, max);
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return -EMSGSIZE;
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}
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/* periodic transfers limit size per frame/uframe,
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* but drivers only control those sizes for ISO.
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* while we're checking, initialize return status.
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*/
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if (temp == PIPE_ISOCHRONOUS) {
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int n, len;
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/* "high bandwidth" mode, 1-3 packets/uframe? */
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if (dev->speed == USB_SPEED_HIGH) {
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int mult = 1 + ((max >> 11) & 0x03);
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max &= 0x07ff;
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max *= mult;
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}
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if (urb->number_of_packets <= 0)
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return -EINVAL;
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for (n = 0; n < urb->number_of_packets; n++) {
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len = urb->iso_frame_desc[n].length;
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if (len < 0 || len > max)
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return -EMSGSIZE;
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urb->iso_frame_desc[n].status = -EXDEV;
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urb->iso_frame_desc[n].actual_length = 0;
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}
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}
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/* the I/O buffer must be mapped/unmapped, except when length=0 */
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if (urb->transfer_buffer_length < 0)
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return -EMSGSIZE;
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#ifdef DEBUG
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/* stuff that drivers shouldn't do, but which shouldn't
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* cause problems in HCDs if they get it wrong.
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*/
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{
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unsigned int orig_flags = urb->transfer_flags;
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unsigned int allowed;
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/* enforce simple/standard policy */
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allowed = (URB_NO_TRANSFER_DMA_MAP | URB_NO_SETUP_DMA_MAP |
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URB_NO_INTERRUPT);
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switch (temp) {
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case PIPE_BULK:
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if (is_out)
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allowed |= URB_ZERO_PACKET;
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/* FALLTHROUGH */
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case PIPE_CONTROL:
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allowed |= URB_NO_FSBR; /* only affects UHCI */
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/* FALLTHROUGH */
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default: /* all non-iso endpoints */
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if (!is_out)
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allowed |= URB_SHORT_NOT_OK;
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break;
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case PIPE_ISOCHRONOUS:
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allowed |= URB_ISO_ASAP;
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break;
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}
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urb->transfer_flags &= allowed;
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/* fail if submitter gave bogus flags */
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if (urb->transfer_flags != orig_flags) {
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err("BOGUS urb flags, %x --> %x",
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orig_flags, urb->transfer_flags);
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return -EINVAL;
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}
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}
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#endif
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/*
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* Force periodic transfer intervals to be legal values that are
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* a power of two (so HCDs don't need to).
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*
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* FIXME want bus->{intr,iso}_sched_horizon values here. Each HC
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* supports different values... this uses EHCI/UHCI defaults (and
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* EHCI can use smaller non-default values).
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*/
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switch (temp) {
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case PIPE_ISOCHRONOUS:
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case PIPE_INTERRUPT:
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/* too small? */
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if (urb->interval <= 0)
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return -EINVAL;
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/* too big? */
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switch (dev->speed) {
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case USB_SPEED_HIGH: /* units are microframes */
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// NOTE usb handles 2^15
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if (urb->interval > (1024 * 8))
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urb->interval = 1024 * 8;
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temp = 1024 * 8;
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break;
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case USB_SPEED_FULL: /* units are frames/msec */
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case USB_SPEED_LOW:
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if (temp == PIPE_INTERRUPT) {
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if (urb->interval > 255)
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return -EINVAL;
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// NOTE ohci only handles up to 32
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temp = 128;
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} else {
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if (urb->interval > 1024)
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urb->interval = 1024;
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// NOTE usb and ohci handle up to 2^15
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temp = 1024;
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}
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break;
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default:
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return -EINVAL;
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}
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/* power of two? */
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while (temp > urb->interval)
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temp >>= 1;
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urb->interval = temp;
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}
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return usb_hcd_submit_urb(urb, mem_flags);
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}
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/*-------------------------------------------------------------------*/
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/**
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* usb_unlink_urb - abort/cancel a transfer request for an endpoint
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* @urb: pointer to urb describing a previously submitted request,
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* may be NULL
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*
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* This routine cancels an in-progress request. URBs complete only once
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* per submission, and may be canceled only once per submission.
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* Successful cancellation means termination of @urb will be expedited
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* and the completion handler will be called with a status code
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* indicating that the request has been canceled (rather than any other
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* code).
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*
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* This request is always asynchronous. Success is indicated by
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* returning -EINPROGRESS, at which time the URB will probably not yet
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* have been given back to the device driver. When it is eventually
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* called, the completion function will see @urb->status == -ECONNRESET.
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* Failure is indicated by usb_unlink_urb() returning any other value.
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* Unlinking will fail when @urb is not currently "linked" (i.e., it was
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* never submitted, or it was unlinked before, or the hardware is already
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* finished with it), even if the completion handler has not yet run.
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*
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* Unlinking and Endpoint Queues:
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*
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* [The behaviors and guarantees described below do not apply to virtual
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* root hubs but only to endpoint queues for physical USB devices.]
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*
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* Host Controller Drivers (HCDs) place all the URBs for a particular
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* endpoint in a queue. Normally the queue advances as the controller
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* hardware processes each request. But when an URB terminates with an
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* error its queue generally stops (see below), at least until that URB's
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* completion routine returns. It is guaranteed that a stopped queue
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* will not restart until all its unlinked URBs have been fully retired,
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* with their completion routines run, even if that's not until some time
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* after the original completion handler returns. The same behavior and
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* guarantee apply when an URB terminates because it was unlinked.
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*
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* Bulk and interrupt endpoint queues are guaranteed to stop whenever an
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* URB terminates with any sort of error, including -ECONNRESET, -ENOENT,
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* and -EREMOTEIO. Control endpoint queues behave the same way except
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* that they are not guaranteed to stop for -EREMOTEIO errors. Queues
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* for isochronous endpoints are treated differently, because they must
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* advance at fixed rates. Such queues do not stop when an URB
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* encounters an error or is unlinked. An unlinked isochronous URB may
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* leave a gap in the stream of packets; it is undefined whether such
|
|
* gaps can be filled in.
|
|
*
|
|
* Note that early termination of an URB because a short packet was
|
|
* received will generate a -EREMOTEIO error if and only if the
|
|
* URB_SHORT_NOT_OK flag is set. By setting this flag, USB device
|
|
* drivers can build deep queues for large or complex bulk transfers
|
|
* and clean them up reliably after any sort of aborted transfer by
|
|
* unlinking all pending URBs at the first fault.
|
|
*
|
|
* When a control URB terminates with an error other than -EREMOTEIO, it
|
|
* is quite likely that the status stage of the transfer will not take
|
|
* place.
|
|
*/
|
|
int usb_unlink_urb(struct urb *urb)
|
|
{
|
|
if (!urb)
|
|
return -EINVAL;
|
|
if (!(urb->dev && urb->dev->bus))
|
|
return -ENODEV;
|
|
return usb_hcd_unlink_urb(urb, -ECONNRESET);
|
|
}
|
|
|
|
/**
|
|
* usb_kill_urb - cancel a transfer request and wait for it to finish
|
|
* @urb: pointer to URB describing a previously submitted request,
|
|
* may be NULL
|
|
*
|
|
* This routine cancels an in-progress request. It is guaranteed that
|
|
* upon return all completion handlers will have finished and the URB
|
|
* will be totally idle and available for reuse. These features make
|
|
* this an ideal way to stop I/O in a disconnect() callback or close()
|
|
* function. If the request has not already finished or been unlinked
|
|
* the completion handler will see urb->status == -ENOENT.
|
|
*
|
|
* While the routine is running, attempts to resubmit the URB will fail
|
|
* with error -EPERM. Thus even if the URB's completion handler always
|
|
* tries to resubmit, it will not succeed and the URB will become idle.
|
|
*
|
|
* This routine may not be used in an interrupt context (such as a bottom
|
|
* half or a completion handler), or when holding a spinlock, or in other
|
|
* situations where the caller can't schedule().
|
|
*/
|
|
void usb_kill_urb(struct urb *urb)
|
|
{
|
|
might_sleep();
|
|
if (!(urb && urb->dev && urb->dev->bus))
|
|
return;
|
|
spin_lock_irq(&urb->lock);
|
|
++urb->reject;
|
|
spin_unlock_irq(&urb->lock);
|
|
|
|
usb_hcd_unlink_urb(urb, -ENOENT);
|
|
wait_event(usb_kill_urb_queue, atomic_read(&urb->use_count) == 0);
|
|
|
|
spin_lock_irq(&urb->lock);
|
|
--urb->reject;
|
|
spin_unlock_irq(&urb->lock);
|
|
}
|
|
|
|
/**
|
|
* usb_kill_anchored_urbs - cancel transfer requests en masse
|
|
* @anchor: anchor the requests are bound to
|
|
*
|
|
* this allows all outstanding URBs to be killed starting
|
|
* from the back of the queue
|
|
*/
|
|
void usb_kill_anchored_urbs(struct usb_anchor *anchor)
|
|
{
|
|
struct urb *victim;
|
|
|
|
spin_lock_irq(&anchor->lock);
|
|
while (!list_empty(&anchor->urb_list)) {
|
|
victim = list_entry(anchor->urb_list.prev, struct urb, anchor_list);
|
|
/* we must make sure the URB isn't freed before we kill it*/
|
|
usb_get_urb(victim);
|
|
spin_unlock_irq(&anchor->lock);
|
|
/* this will unanchor the URB */
|
|
usb_kill_urb(victim);
|
|
usb_put_urb(victim);
|
|
spin_lock_irq(&anchor->lock);
|
|
}
|
|
spin_unlock_irq(&anchor->lock);
|
|
}
|
|
EXPORT_SYMBOL_GPL(usb_kill_anchored_urbs);
|
|
|
|
/**
|
|
* usb_wait_anchor_empty_timeout - wait for an anchor to be unused
|
|
* @anchor: the anchor you want to become unused
|
|
* @timeout: how long you are willing to wait in milliseconds
|
|
*
|
|
* Call this is you want to be sure all an anchor's
|
|
* URBs have finished
|
|
*/
|
|
int usb_wait_anchor_empty_timeout(struct usb_anchor *anchor,
|
|
unsigned int timeout)
|
|
{
|
|
return wait_event_timeout(anchor->wait, list_empty(&anchor->urb_list),
|
|
msecs_to_jiffies(timeout));
|
|
}
|
|
EXPORT_SYMBOL_GPL(usb_wait_anchor_empty_timeout);
|
|
|
|
EXPORT_SYMBOL(usb_init_urb);
|
|
EXPORT_SYMBOL(usb_alloc_urb);
|
|
EXPORT_SYMBOL(usb_free_urb);
|
|
EXPORT_SYMBOL(usb_get_urb);
|
|
EXPORT_SYMBOL(usb_submit_urb);
|
|
EXPORT_SYMBOL(usb_unlink_urb);
|
|
EXPORT_SYMBOL(usb_kill_urb);
|