![Alan Stern](/assets/img/avatar_default.png)
In response to complaints about excessive latency in the uhci-hcd driver I'm planning to convert it to a top-half/bottom-half design. It turns out that to do this, the USB API has to be modified slightly since the driver will not be able to meet one of the guarantees in the current API. This patch changes some kerneldoc, specifying the weaker guarantee. Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
516 lines
18 KiB
C
516 lines
18 KiB
C
#include <linux/config.h>
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#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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#ifdef CONFIG_USB_DEBUG
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#define DEBUG
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#else
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#undef DEBUG
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#endif
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#include <linux/usb.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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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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}
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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, int mem_flags)
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{
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struct urb *urb;
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urb = (struct 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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/**
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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 cancelation").
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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 cancelation).
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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, int 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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struct usb_operations *op;
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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->state == USB_STATE_SUSPENDED)
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return -EHOSTUNREACH;
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if (!(op = dev->bus->op) || !op->submit_urb)
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return -ENODEV;
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urb->status = -EINPROGRESS;
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urb->actual_length = 0;
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urb->bandwidth = 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_ASYNC_UNLINK; // affects later unlinks
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allowed |= (URB_NO_TRANSFER_DMA_MAP | URB_NO_SETUP_DMA_MAP);
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allowed |= 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 op->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
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* once per submission, and may be canceled only once per submission.
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* Successful cancelation means the requests's completion handler will
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* be called with a status code indicating that the request has been
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* canceled (rather than any other code) and will quickly be removed
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* from host controller data structures.
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*
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* In the past, clearing the URB_ASYNC_UNLINK transfer flag for the
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* URB indicated that the request was synchronous. This usage is now
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* deprecated; if the flag is clear the call will be forwarded to
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* usb_kill_urb() and the return value will be 0. In the future, drivers
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* should call usb_kill_urb() directly for synchronous unlinking.
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*
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* When the URB_ASYNC_UNLINK transfer flag for the URB is set, this
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* request is asynchronous. Success is indicated by returning -EINPROGRESS,
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* at which time the URB will normally have been unlinked but not yet
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* given back to the device driver. When it is called, the completion
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* function will see urb->status == -ECONNRESET. Failure is indicated
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* by any other return value. Unlinking will fail when the URB is not
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* currently "linked" (i.e., it was never submitted, or it was unlinked
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* before, or the hardware is already finished with it), even if the
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* 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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* 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 stops, at least until that URB's completion routine
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* returns. It is guaranteed that the queue will not restart until all
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* its unlinked URBs have been fully retired, with their completion
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* routines run, even if that's not until some time after the original
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* completion handler returns. Normally the same behavior and guarantees
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* apply when an URB terminates because it was unlinked; however if an
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* URB is unlinked before the hardware has started to execute it, then
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* its queue is not guaranteed to stop until all the preceding URBs have
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* completed.
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*
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* This means that USB device drivers can safely build deep queues for
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* large or complex transfers, and clean them up reliably after any sort
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* of aborted transfer by unlinking all pending URBs at the first fault.
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*
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* Note that an URB terminating early because a short packet was received
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* will count as an error if and only if the URB_SHORT_NOT_OK flag is set.
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* Also, that all unlinks performed in any URB completion handler must
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* be asynchronous.
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*
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* Queues for isochronous endpoints are treated differently, because they
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* advance at fixed rates. Such queues do not stop when an URB is unlinked.
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* An unlinked URB may leave a gap in the stream of packets. It is undefined
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* whether such gaps can be filled in.
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*
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* When a control URB terminates with an error, it is likely that the
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* status stage of the transfer will not take place, even if it is merely
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* a soft error resulting from a short-packet with URB_SHORT_NOT_OK set.
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*/
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int usb_unlink_urb(struct urb *urb)
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{
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if (!urb)
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return -EINVAL;
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if (!(urb->transfer_flags & URB_ASYNC_UNLINK)) {
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#ifdef CONFIG_DEBUG_KERNEL
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if (printk_ratelimit()) {
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printk(KERN_NOTICE "usb_unlink_urb() is deprecated for "
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"synchronous unlinks. Use usb_kill_urb() instead.\n");
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WARN_ON(1);
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}
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#endif
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usb_kill_urb(urb);
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return 0;
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}
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if (!(urb->dev && urb->dev->bus && urb->dev->bus->op))
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return -ENODEV;
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return urb->dev->bus->op->unlink_urb(urb, -ECONNRESET);
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}
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/**
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* 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)
|
|
{
|
|
if (!(urb && urb->dev && urb->dev->bus && urb->dev->bus->op))
|
|
return;
|
|
spin_lock_irq(&urb->lock);
|
|
++urb->reject;
|
|
spin_unlock_irq(&urb->lock);
|
|
|
|
urb->dev->bus->op->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);
|
|
}
|
|
|
|
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);
|
|
|