Linux-2.6.33.2/drivers/parport/share.c
/*
* Parallel-port resource manager code.
*
* Authors: David Campbell <campbell@tirian.che.curtin.edu.au>
* Tim Waugh <tim@cyberelk.demon.co.uk>
* Jose Renau <renau@acm.org>
* Philip Blundell <philb@gnu.org>
* Andrea Arcangeli
*
* based on work by Grant Guenther <grant@torque.net>
* and Philip Blundell
*
* Any part of this program may be used in documents licensed under
* the GNU Free Documentation License, Version 1.1 or any later version
* published by the Free Software Foundation.
*/
#undef PARPORT_DEBUG_SHARING /* undef for production */
#include <linux/module.h>
#include <linux/string.h>
#include <linux/threads.h>
#include <linux/parport.h>
#include <linux/delay.h>
#include <linux/errno.h>
#include <linux/interrupt.h>
#include <linux/ioport.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/kmod.h>
#include <linux/spinlock.h>
#include <linux/mutex.h>
#include <asm/irq.h>
#undef PARPORT_PARANOID
#define PARPORT_DEFAULT_TIMESLICE (HZ/5)
unsigned long parport_default_timeslice = PARPORT_DEFAULT_TIMESLICE;
int parport_default_spintime = DEFAULT_SPIN_TIME;
static LIST_HEAD(portlist);
static DEFINE_SPINLOCK(parportlist_lock);
/* list of all allocated ports, sorted by ->number */
static LIST_HEAD(all_ports);
static DEFINE_SPINLOCK(full_list_lock);
static LIST_HEAD(drivers);
static DEFINE_MUTEX(registration_lock);
/* What you can do to a port that's gone away.. */
static void dead_write_lines (struct parport *p, unsigned char b){}
static unsigned char dead_read_lines (struct parport *p) { return 0; }
static unsigned char dead_frob_lines (struct parport *p, unsigned char b,
unsigned char c) { return 0; }
static void dead_onearg (struct parport *p){}
static void dead_initstate (struct pardevice *d, struct parport_state *s) { }
static void dead_state (struct parport *p, struct parport_state *s) { }
static size_t dead_write (struct parport *p, const void *b, size_t l, int f)
{ return 0; }
static size_t dead_read (struct parport *p, void *b, size_t l, int f)
{ return 0; }
static struct parport_operations dead_ops = {
.write_data = dead_write_lines, /* data */
.read_data = dead_read_lines,
.write_control = dead_write_lines, /* control */
.read_control = dead_read_lines,
.frob_control = dead_frob_lines,
.read_status = dead_read_lines, /* status */
.enable_irq = dead_onearg, /* enable_irq */
.disable_irq = dead_onearg, /* disable_irq */
.data_forward = dead_onearg, /* data_forward */
.data_reverse = dead_onearg, /* data_reverse */
.init_state = dead_initstate, /* init_state */
.save_state = dead_state,
.restore_state = dead_state,
.epp_write_data = dead_write, /* epp */
.epp_read_data = dead_read,
.epp_write_addr = dead_write,
.epp_read_addr = dead_read,
.ecp_write_data = dead_write, /* ecp */
.ecp_read_data = dead_read,
.ecp_write_addr = dead_write,
.compat_write_data = dead_write, /* compat */
.nibble_read_data = dead_read, /* nibble */
.byte_read_data = dead_read, /* byte */
.owner = NULL,
};
/* Call attach(port) for each registered driver. */
static void attach_driver_chain(struct parport *port)
{
/* caller has exclusive registration_lock */
struct parport_driver *drv;
list_for_each_entry(drv, &drivers, list)
drv->attach(port);
}
/* Call detach(port) for each registered driver. */
static void detach_driver_chain(struct parport *port)
{
struct parport_driver *drv;
/* caller has exclusive registration_lock */
list_for_each_entry(drv, &drivers, list)
drv->detach (port);
}
/* Ask kmod for some lowlevel drivers. */
static void get_lowlevel_driver (void)
{
/* There is no actual module called this: you should set
* up an alias for modutils. */
request_module ("parport_lowlevel");
}
/**
* parport_register_driver - register a parallel port device driver
* @drv: structure describing the driver
*
* This can be called by a parallel port device driver in order
* to receive notifications about ports being found in the
* system, as well as ports no longer available.
*
* The @drv structure is allocated by the caller and must not be
* deallocated until after calling parport_unregister_driver().
*
* The driver's attach() function may block. The port that
* attach() is given will be valid for the duration of the
* callback, but if the driver wants to take a copy of the
* pointer it must call parport_get_port() to do so. Calling
* parport_register_device() on that port will do this for you.
*
* The driver's detach() function may block. The port that
* detach() is given will be valid for the duration of the
* callback, but if the driver wants to take a copy of the
* pointer it must call parport_get_port() to do so.
*
* Returns 0 on success. Currently it always succeeds.
**/
int parport_register_driver (struct parport_driver *drv)
{
struct parport *port;
if (list_empty(&portlist))
get_lowlevel_driver ();
mutex_lock(®istration_lock);
list_for_each_entry(port, &portlist, list)
drv->attach(port);
list_add(&drv->list, &drivers);
mutex_unlock(®istration_lock);
return 0;
}
/**
* parport_unregister_driver - deregister a parallel port device driver
* @drv: structure describing the driver that was given to
* parport_register_driver()
*
* This should be called by a parallel port device driver that
* has registered itself using parport_register_driver() when it
* is about to be unloaded.
*
* When it returns, the driver's attach() routine will no longer
* be called, and for each port that attach() was called for, the
* detach() routine will have been called.
*
* All the driver's attach() and detach() calls are guaranteed to have
* finished by the time this function returns.
**/
void parport_unregister_driver (struct parport_driver *drv)
{
struct parport *port;
mutex_lock(®istration_lock);
list_del_init(&drv->list);
list_for_each_entry(port, &portlist, list)
drv->detach(port);
mutex_unlock(®istration_lock);
}
static void free_port (struct parport *port)
{
int d;
spin_lock(&full_list_lock);
list_del(&port->full_list);
spin_unlock(&full_list_lock);
for (d = 0; d < 5; d++) {
kfree(port->probe_info[d].class_name);
kfree(port->probe_info[d].mfr);
kfree(port->probe_info[d].model);
kfree(port->probe_info[d].cmdset);
kfree(port->probe_info[d].description);
}
kfree(port->name);
kfree(port);
}
/**
* parport_get_port - increment a port's reference count
* @port: the port
*
* This ensures that a struct parport pointer remains valid
* until the matching parport_put_port() call.
**/
struct parport *parport_get_port (struct parport *port)
{
atomic_inc (&port->ref_count);
return port;
}
/**
* parport_put_port - decrement a port's reference count
* @port: the port
*
* This should be called once for each call to parport_get_port(),
* once the port is no longer needed.
**/
void parport_put_port (struct parport *port)
{
if (atomic_dec_and_test (&port->ref_count))
/* Can destroy it now. */
free_port (port);
return;
}
/**
* parport_register_port - register a parallel port
* @base: base I/O address
* @irq: IRQ line
* @dma: DMA channel
* @ops: pointer to the port driver's port operations structure
*
* When a parallel port (lowlevel) driver finds a port that
* should be made available to parallel port device drivers, it
* should call parport_register_port(). The @base, @irq, and
* @dma parameters are for the convenience of port drivers, and
* for ports where they aren't meaningful needn't be set to
* anything special. They can be altered afterwards by adjusting
* the relevant members of the parport structure that is returned
* and represents the port. They should not be tampered with
* after calling parport_announce_port, however.
*
* If there are parallel port device drivers in the system that
* have registered themselves using parport_register_driver(),
* they are not told about the port at this time; that is done by
* parport_announce_port().
*
* The @ops structure is allocated by the caller, and must not be
* deallocated before calling parport_remove_port().
*
* If there is no memory to allocate a new parport structure,
* this function will return %NULL.
**/
struct parport *parport_register_port(unsigned long base, int irq, int dma,
struct parport_operations *ops)
{
struct list_head *l;
struct parport *tmp;
int num;
int device;
char *name;
tmp = kmalloc(sizeof(struct parport), GFP_KERNEL);
if (!tmp) {
printk(KERN_WARNING "parport: memory squeeze\n");
return NULL;
}
/* Init our structure */
memset(tmp, 0, sizeof(struct parport));
tmp->base = base;
tmp->irq = irq;
tmp->dma = dma;
tmp->muxport = tmp->daisy = tmp->muxsel = -1;
tmp->modes = 0;
INIT_LIST_HEAD(&tmp->list);
tmp->devices = tmp->cad = NULL;
tmp->flags = 0;
tmp->ops = ops;
tmp->physport = tmp;
memset (tmp->probe_info, 0, 5 * sizeof (struct parport_device_info));
rwlock_init(&tmp->cad_lock);
spin_lock_init(&tmp->waitlist_lock);
spin_lock_init(&tmp->pardevice_lock);
tmp->ieee1284.mode = IEEE1284_MODE_COMPAT;
tmp->ieee1284.phase = IEEE1284_PH_FWD_IDLE;
init_MUTEX_LOCKED (&tmp->ieee1284.irq); /* actually a semaphore at 0 */
tmp->spintime = parport_default_spintime;
atomic_set (&tmp->ref_count, 1);
INIT_LIST_HEAD(&tmp->full_list);
name = kmalloc(15, GFP_KERNEL);
if (!name) {
printk(KERN_ERR "parport: memory squeeze\n");
kfree(tmp);
return NULL;
}
/* Search for the lowest free parport number. */
spin_lock(&full_list_lock);
for (l = all_ports.next, num = 0; l != &all_ports; l = l->next, num++) {
struct parport *p = list_entry(l, struct parport, full_list);
if (p->number != num)
break;
}
tmp->portnum = tmp->number = num;
list_add_tail(&tmp->full_list, l);
spin_unlock(&full_list_lock);
/*
* Now that the portnum is known finish doing the Init.
*/
sprintf(name, "parport%d", tmp->portnum = tmp->number);
tmp->name = name;
for (device = 0; device < 5; device++)
/* assume the worst */
tmp->probe_info[device].class = PARPORT_CLASS_LEGACY;
tmp->waithead = tmp->waittail = NULL;
return tmp;
}
/**
* parport_announce_port - tell device drivers about a parallel port
* @port: parallel port to announce
*
* After a port driver has registered a parallel port with
* parport_register_port, and performed any necessary
* initialisation or adjustments, it should call
* parport_announce_port() in order to notify all device drivers
* that have called parport_register_driver(). Their attach()
* functions will be called, with @port as the parameter.
**/
void parport_announce_port (struct parport *port)
{
int i;
#ifdef CONFIG_PARPORT_1284
/* Analyse the IEEE1284.3 topology of the port. */
parport_daisy_init(port);
#endif
if (!port->dev)
printk(KERN_WARNING "%s: fix this legacy "
"no-device port driver!\n",
port->name);
parport_proc_register(port);
mutex_lock(®istration_lock);
spin_lock_irq(&parportlist_lock);
list_add_tail(&port->list, &portlist);
for (i = 1; i < 3; i++) {
struct parport *slave = port->slaves[i-1];
if (slave)
list_add_tail(&slave->list, &portlist);
}
spin_unlock_irq(&parportlist_lock);
/* Let drivers know that new port(s) has arrived. */
attach_driver_chain (port);
for (i = 1; i < 3; i++) {
struct parport *slave = port->slaves[i-1];
if (slave)
attach_driver_chain(slave);
}
mutex_unlock(®istration_lock);
}
/**
* parport_remove_port - deregister a parallel port
* @port: parallel port to deregister
*
* When a parallel port driver is forcibly unloaded, or a
* parallel port becomes inaccessible, the port driver must call
* this function in order to deal with device drivers that still
* want to use it.
*
* The parport structure associated with the port has its
* operations structure replaced with one containing 'null'
* operations that return errors or just don't do anything.
*
* Any drivers that have registered themselves using
* parport_register_driver() are notified that the port is no
* longer accessible by having their detach() routines called
* with @port as the parameter.
**/
void parport_remove_port(struct parport *port)
{
int i;
mutex_lock(®istration_lock);
/* Spread the word. */
detach_driver_chain (port);
#ifdef CONFIG_PARPORT_1284
/* Forget the IEEE1284.3 topology of the port. */
parport_daisy_fini(port);
for (i = 1; i < 3; i++) {
struct parport *slave = port->slaves[i-1];
if (!slave)
continue;
detach_driver_chain(slave);
parport_daisy_fini(slave);
}
#endif
port->ops = &dead_ops;
spin_lock(&parportlist_lock);
list_del_init(&port->list);
for (i = 1; i < 3; i++) {
struct parport *slave = port->slaves[i-1];
if (slave)
list_del_init(&slave->list);
}
spin_unlock(&parportlist_lock);
mutex_unlock(®istration_lock);
parport_proc_unregister(port);
for (i = 1; i < 3; i++) {
struct parport *slave = port->slaves[i-1];
if (slave)
parport_put_port(slave);
}
}
/**
* parport_register_device - register a device on a parallel port
* @port: port to which the device is attached
* @name: a name to refer to the device
* @pf: preemption callback
* @kf: kick callback (wake-up)
* @irq_func: interrupt handler
* @flags: registration flags
* @handle: data for callback functions
*
* This function, called by parallel port device drivers,
* declares that a device is connected to a port, and tells the
* system all it needs to know.
*
* The @name is allocated by the caller and must not be
* deallocated until the caller calls @parport_unregister_device
* for that device.
*
* The preemption callback function, @pf, is called when this
* device driver has claimed access to the port but another
* device driver wants to use it. It is given @handle as its
* parameter, and should return zero if it is willing for the
* system to release the port to another driver on its behalf.
* If it wants to keep control of the port it should return
* non-zero, and no action will be taken. It is good manners for
* the driver to try to release the port at the earliest
* opportunity after its preemption callback rejects a preemption
* attempt. Note that if a preemption callback is happy for
* preemption to go ahead, there is no need to release the port;
* it is done automatically. This function may not block, as it
* may be called from interrupt context. If the device driver
* does not support preemption, @pf can be %NULL.
*
* The wake-up ("kick") callback function, @kf, is called when
* the port is available to be claimed for exclusive access; that
* is, parport_claim() is guaranteed to succeed when called from
* inside the wake-up callback function. If the driver wants to
* claim the port it should do so; otherwise, it need not take
* any action. This function may not block, as it may be called
* from interrupt context. If the device driver does not want to
* be explicitly invited to claim the port in this way, @kf can
* be %NULL.
*
* The interrupt handler, @irq_func, is called when an interrupt
* arrives from the parallel port. Note that if a device driver
* wants to use interrupts it should use parport_enable_irq(),
* and can also check the irq member of the parport structure
* representing the port.
*
* The parallel port (lowlevel) driver is the one that has called
* request_irq() and whose interrupt handler is called first.
* This handler does whatever needs to be done to the hardware to
* acknowledge the interrupt (for PC-style ports there is nothing
* special to be done). It then tells the IEEE 1284 code about
* the interrupt, which may involve reacting to an IEEE 1284
* event depending on the current IEEE 1284 phase. After this,
* it calls @irq_func. Needless to say, @irq_func will be called
* from interrupt context, and may not block.
*
* The %PARPORT_DEV_EXCL flag is for preventing port sharing, and
* so should only be used when sharing the port with other device
* drivers is impossible and would lead to incorrect behaviour.
* Use it sparingly! Normally, @flags will be zero.
*
* This function returns a pointer to a structure that represents
* the device on the port, or %NULL if there is not enough memory
* to allocate space for that structure.
**/
struct pardevice *
parport_register_device(struct parport *port, const char *name,
int (*pf)(void *), void (*kf)(void *),
void (*irq_func)(void *),
int flags, void *handle)
{
struct pardevice *tmp;
if (port->physport->flags & PARPORT_FLAG_EXCL) {
/* An exclusive device is registered. */
printk (KERN_DEBUG "%s: no more devices allowed\n",
port->name);
return NULL;
}
if (flags & PARPORT_DEV_LURK) {
if (!pf || !kf) {
printk(KERN_INFO "%s: refused to register lurking device (%s) without callbacks\n", port->name, name);
return NULL;
}
}
/* We up our own module reference count, and that of the port
on which a device is to be registered, to ensure that
neither of us gets unloaded while we sleep in (e.g.)
kmalloc.
*/
if (!try_module_get(port->ops->owner)) {
return NULL;
}
parport_get_port (port);
tmp = kmalloc(sizeof(struct pardevice), GFP_KERNEL);
if (tmp == NULL) {
printk(KERN_WARNING "%s: memory squeeze, couldn't register %s.\n", port->name, name);
goto out;
}
tmp->state = kmalloc(sizeof(struct parport_state), GFP_KERNEL);
if (tmp->state == NULL) {
printk(KERN_WARNING "%s: memory squeeze, couldn't register %s.\n", port->name, name);
goto out_free_pardevice;
}
tmp->name = name;
tmp->port = port;
tmp->daisy = -1;
tmp->preempt = pf;
tmp->wakeup = kf;
tmp->private = handle;
tmp->flags = flags;
tmp->irq_func = irq_func;
tmp->waiting = 0;
tmp->timeout = 5 * HZ;
/* Chain this onto the list */
tmp->prev = NULL;
/*
* This function must not run from an irq handler so we don' t need
* to clear irq on the local CPU. -arca
*/
spin_lock(&port->physport->pardevice_lock);
if (flags & PARPORT_DEV_EXCL) {
if (port->physport->devices) {
spin_unlock (&port->physport->pardevice_lock);
printk (KERN_DEBUG
"%s: cannot grant exclusive access for "
"device %s\n", port->name, name);
goto out_free_all;
}
port->flags |= PARPORT_FLAG_EXCL;
}
tmp->next = port->physport->devices;
wmb(); /* Make sure that tmp->next is written before it's
added to the list; see comments marked 'no locking
required' */
if (port->physport->devices)
port->physport->devices->prev = tmp;
port->physport->devices = tmp;
spin_unlock(&port->physport->pardevice_lock);
init_waitqueue_head(&tmp->wait_q);
tmp->timeslice = parport_default_timeslice;
tmp->waitnext = tmp->waitprev = NULL;
/*
* This has to be run as last thing since init_state may need other
* pardevice fields. -arca
*/
port->ops->init_state(tmp, tmp->state);
if (!test_and_set_bit(PARPORT_DEVPROC_REGISTERED, &port->devflags)) {
port->proc_device = tmp;
parport_device_proc_register(tmp);
}
return tmp;
out_free_all:
kfree(tmp->state);
out_free_pardevice:
kfree(tmp);
out:
parport_put_port (port);
module_put(port->ops->owner);
return NULL;
}
/**
* parport_unregister_device - deregister a device on a parallel port
* @dev: pointer to structure representing device
*
* This undoes the effect of parport_register_device().
**/
void parport_unregister_device(struct pardevice *dev)
{
struct parport *port;
#ifdef PARPORT_PARANOID
if (dev == NULL) {
printk(KERN_ERR "parport_unregister_device: passed NULL\n");
return;
}
#endif
port = dev->port->physport;
if (port->proc_device == dev) {
port->proc_device = NULL;
clear_bit(PARPORT_DEVPROC_REGISTERED, &port->devflags);
parport_device_proc_unregister(dev);
}
if (port->cad == dev) {
printk(KERN_DEBUG "%s: %s forgot to release port\n",
port->name, dev->name);
parport_release (dev);
}
spin_lock(&port->pardevice_lock);
if (dev->next)
dev->next->prev = dev->prev;
if (dev->prev)
dev->prev->next = dev->next;
else
port->devices = dev->next;
if (dev->flags & PARPORT_DEV_EXCL)
port->flags &= ~PARPORT_FLAG_EXCL;
spin_unlock(&port->pardevice_lock);
/* Make sure we haven't left any pointers around in the wait
* list. */
spin_lock (&port->waitlist_lock);
if (dev->waitprev || dev->waitnext || port->waithead == dev) {
if (dev->waitprev)
dev->waitprev->waitnext = dev->waitnext;
else
port->waithead = dev->waitnext;
if (dev->waitnext)
dev->waitnext->waitprev = dev->waitprev;
else
port->waittail = dev->waitprev;
}
spin_unlock (&port->waitlist_lock);
kfree(dev->state);
kfree(dev);
module_put(port->ops->owner);
parport_put_port (port);
}
/**
* parport_find_number - find a parallel port by number
* @number: parallel port number
*
* This returns the parallel port with the specified number, or
* %NULL if there is none.
*
* There is an implicit parport_get_port() done already; to throw
* away the reference to the port that parport_find_number()
* gives you, use parport_put_port().
*/
struct parport *parport_find_number (int number)
{
struct parport *port, *result = NULL;
if (list_empty(&portlist))
get_lowlevel_driver ();
spin_lock (&parportlist_lock);
list_for_each_entry(port, &portlist, list) {
if (port->number == number) {
result = parport_get_port (port);
break;
}
}
spin_unlock (&parportlist_lock);
return result;
}
/**
* parport_find_base - find a parallel port by base address
* @base: base I/O address
*
* This returns the parallel port with the specified base
* address, or %NULL if there is none.
*
* There is an implicit parport_get_port() done already; to throw
* away the reference to the port that parport_find_base()
* gives you, use parport_put_port().
*/
struct parport *parport_find_base (unsigned long base)
{
struct parport *port, *result = NULL;
if (list_empty(&portlist))
get_lowlevel_driver ();
spin_lock (&parportlist_lock);
list_for_each_entry(port, &portlist, list) {
if (port->base == base) {
result = parport_get_port (port);
break;
}
}
spin_unlock (&parportlist_lock);
return result;
}
/**
* parport_claim - claim access to a parallel port device
* @dev: pointer to structure representing a device on the port
*
* This function will not block and so can be used from interrupt
* context. If parport_claim() succeeds in claiming access to
* the port it returns zero and the port is available to use. It
* may fail (returning non-zero) if the port is in use by another
* driver and that driver is not willing to relinquish control of
* the port.
**/
int parport_claim(struct pardevice *dev)
{
struct pardevice *oldcad;
struct parport *port = dev->port->physport;
unsigned long flags;
if (port->cad == dev) {
printk(KERN_INFO "%s: %s already owner\n",
dev->port->name,dev->name);
return 0;
}
/* Preempt any current device */
write_lock_irqsave (&port->cad_lock, flags);
if ((oldcad = port->cad) != NULL) {
if (oldcad->preempt) {
if (oldcad->preempt(oldcad->private))
goto blocked;
port->ops->save_state(port, dev->state);
} else
goto blocked;
if (port->cad != oldcad) {
/* I think we'll actually deadlock rather than
get here, but just in case.. */
printk(KERN_WARNING
"%s: %s released port when preempted!\n",
port->name, oldcad->name);
if (port->cad)
goto blocked;
}
}
/* Can't fail from now on, so mark ourselves as no longer waiting. */
if (dev->waiting & 1) {
dev->waiting = 0;
/* Take ourselves out of the wait list again. */
spin_lock_irq (&port->waitlist_lock);
if (dev->waitprev)
dev->waitprev->waitnext = dev->waitnext;
else
port->waithead = dev->waitnext;
if (dev->waitnext)
dev->waitnext->waitprev = dev->waitprev;
else
port->waittail = dev->waitprev;
spin_unlock_irq (&port->waitlist_lock);
dev->waitprev = dev->waitnext = NULL;
}
/* Now we do the change of devices */
port->cad = dev;
#ifdef CONFIG_PARPORT_1284
/* If it's a mux port, select it. */
if (dev->port->muxport >= 0) {
/* FIXME */
port->muxsel = dev->port->muxport;
}
/* If it's a daisy chain device, select it. */
if (dev->daisy >= 0) {
/* This could be lazier. */
if (!parport_daisy_select (port, dev->daisy,
IEEE1284_MODE_COMPAT))
port->daisy = dev->daisy;
}
#endif /* IEEE1284.3 support */
/* Restore control registers */
port->ops->restore_state(port, dev->state);
write_unlock_irqrestore(&port->cad_lock, flags);
dev->time = jiffies;
return 0;
blocked:
/* If this is the first time we tried to claim the port, register an
interest. This is only allowed for devices sleeping in
parport_claim_or_block(), or those with a wakeup function. */
/* The cad_lock is still held for writing here */
if (dev->waiting & 2 || dev->wakeup) {
spin_lock (&port->waitlist_lock);
if (test_and_set_bit(0, &dev->waiting) == 0) {
/* First add ourselves to the end of the wait list. */
dev->waitnext = NULL;
dev->waitprev = port->waittail;
if (port->waittail) {
port->waittail->waitnext = dev;
port->waittail = dev;
} else
port->waithead = port->waittail = dev;
}
spin_unlock (&port->waitlist_lock);
}
write_unlock_irqrestore (&port->cad_lock, flags);
return -EAGAIN;
}
/**
* parport_claim_or_block - claim access to a parallel port device
* @dev: pointer to structure representing a device on the port
*
* This behaves like parport_claim(), but will block if necessary
* to wait for the port to be free. A return value of 1
* indicates that it slept; 0 means that it succeeded without
* needing to sleep. A negative error code indicates failure.
**/
int parport_claim_or_block(struct pardevice *dev)
{
int r;
/* Signal to parport_claim() that we can wait even without a
wakeup function. */
dev->waiting = 2;
/* Try to claim the port. If this fails, we need to sleep. */
r = parport_claim(dev);
if (r == -EAGAIN) {
#ifdef PARPORT_DEBUG_SHARING
printk(KERN_DEBUG "%s: parport_claim() returned -EAGAIN\n", dev->name);
#endif
/*
* FIXME!!! Use the proper locking for dev->waiting,
* and make this use the "wait_event_interruptible()"
* interfaces. The cli/sti that used to be here
* did nothing.
*
* See also parport_release()
*/
/* If dev->waiting is clear now, an interrupt
gave us the port and we would deadlock if we slept. */
if (dev->waiting) {
interruptible_sleep_on (&dev->wait_q);
if (signal_pending (current)) {
return -EINTR;
}
r = 1;
} else {
r = 0;
#ifdef PARPORT_DEBUG_SHARING
printk(KERN_DEBUG "%s: didn't sleep in parport_claim_or_block()\n",
dev->name);
#endif
}
#ifdef PARPORT_DEBUG_SHARING
if (dev->port->physport->cad != dev)
printk(KERN_DEBUG "%s: exiting parport_claim_or_block "
"but %s owns port!\n", dev->name,
dev->port->physport->cad ?
dev->port->physport->cad->name:"nobody");
#endif
}
dev->waiting = 0;
return r;
}
/**
* parport_release - give up access to a parallel port device
* @dev: pointer to structure representing parallel port device
*
* This function cannot fail, but it should not be called without
* the port claimed. Similarly, if the port is already claimed
* you should not try claiming it again.
**/
void parport_release(struct pardevice *dev)
{
struct parport *port = dev->port->physport;
struct pardevice *pd;
unsigned long flags;
/* Make sure that dev is the current device */
write_lock_irqsave(&port->cad_lock, flags);
if (port->cad != dev) {
write_unlock_irqrestore (&port->cad_lock, flags);
printk(KERN_WARNING "%s: %s tried to release parport "
"when not owner\n", port->name, dev->name);
return;
}
#ifdef CONFIG_PARPORT_1284
/* If this is on a mux port, deselect it. */
if (dev->port->muxport >= 0) {
/* FIXME */
port->muxsel = -1;
}
/* If this is a daisy device, deselect it. */
if (dev->daisy >= 0) {
parport_daisy_deselect_all (port);
port->daisy = -1;
}
#endif
port->cad = NULL;
write_unlock_irqrestore(&port->cad_lock, flags);
/* Save control registers */
port->ops->save_state(port, dev->state);
/* If anybody is waiting, find out who's been there longest and
then wake them up. (Note: no locking required) */
/* !!! LOCKING IS NEEDED HERE */
for (pd = port->waithead; pd; pd = pd->waitnext) {
if (pd->waiting & 2) { /* sleeping in claim_or_block */
parport_claim(pd);
if (waitqueue_active(&pd->wait_q))
wake_up_interruptible(&pd->wait_q);
return;
} else if (pd->wakeup) {
pd->wakeup(pd->private);
if (dev->port->cad) /* racy but no matter */
return;
} else {
printk(KERN_ERR "%s: don't know how to wake %s\n", port->name, pd->name);
}
}
/* Nobody was waiting, so walk the list to see if anyone is
interested in being woken up. (Note: no locking required) */
/* !!! LOCKING IS NEEDED HERE */
for (pd = port->devices; (port->cad == NULL) && pd; pd = pd->next) {
if (pd->wakeup && pd != dev)
pd->wakeup(pd->private);
}
}
irqreturn_t parport_irq_handler(int irq, void *dev_id)
{
struct parport *port = dev_id;
parport_generic_irq(port);
return IRQ_HANDLED;
}
/* Exported symbols for modules. */
EXPORT_SYMBOL(parport_claim);
EXPORT_SYMBOL(parport_claim_or_block);
EXPORT_SYMBOL(parport_release);
EXPORT_SYMBOL(parport_register_port);
EXPORT_SYMBOL(parport_announce_port);
EXPORT_SYMBOL(parport_remove_port);
EXPORT_SYMBOL(parport_register_driver);
EXPORT_SYMBOL(parport_unregister_driver);
EXPORT_SYMBOL(parport_register_device);
EXPORT_SYMBOL(parport_unregister_device);
EXPORT_SYMBOL(parport_get_port);
EXPORT_SYMBOL(parport_put_port);
EXPORT_SYMBOL(parport_find_number);
EXPORT_SYMBOL(parport_find_base);
EXPORT_SYMBOL(parport_irq_handler);
MODULE_LICENSE("GPL");