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linux-next/drivers/char/hvc_console.c
David Howells 7d12e780e0 IRQ: Maintain regs pointer globally rather than passing to IRQ handlers 
Maintain a per-CPU global "struct pt_regs *" variable which can be used instead
of passing regs around manually through all ~1800 interrupt handlers in the
Linux kernel.

The regs pointer is used in few places, but it potentially costs both stack
space and code to pass it around.  On the FRV arch, removing the regs parameter
from all the genirq function results in a 20% speed up of the IRQ exit path
(ie: from leaving timer_interrupt() to leaving do_IRQ()).

Where appropriate, an arch may override the generic storage facility and do
something different with the variable.  On FRV, for instance, the address is
maintained in GR28 at all times inside the kernel as part of general exception
handling.

Having looked over the code, it appears that the parameter may be handed down
through up to twenty or so layers of functions.  Consider a USB character
device attached to a USB hub, attached to a USB controller that posts its
interrupts through a cascaded auxiliary interrupt controller.  A character
device driver may want to pass regs to the sysrq handler through the input
layer which adds another few layers of parameter passing.

I've build this code with allyesconfig for x86_64 and i386.  I've runtested the
main part of the code on FRV and i386, though I can't test most of the drivers.
I've also done partial conversion for powerpc and MIPS - these at least compile
with minimal configurations.

This will affect all archs.  Mostly the changes should be relatively easy.
Take do_IRQ(), store the regs pointer at the beginning, saving the old one:

	struct pt_regs *old_regs = set_irq_regs(regs);

And put the old one back at the end:

	set_irq_regs(old_regs);

Don't pass regs through to generic_handle_irq() or __do_IRQ().

In timer_interrupt(), this sort of change will be necessary:

	-	update_process_times(user_mode(regs));
	-	profile_tick(CPU_PROFILING, regs);
	+	update_process_times(user_mode(get_irq_regs()));
	+	profile_tick(CPU_PROFILING);

I'd like to move update_process_times()'s use of get_irq_regs() into itself,
except that i386, alone of the archs, uses something other than user_mode().

Some notes on the interrupt handling in the drivers:

 (*) input_dev() is now gone entirely.  The regs pointer is no longer stored in
     the input_dev struct.

 (*) finish_unlinks() in drivers/usb/host/ohci-q.c needs checking.  It does
     something different depending on whether it's been supplied with a regs
     pointer or not.

 (*) Various IRQ handler function pointers have been moved to type
     irq_handler_t.

Signed-Off-By: David Howells <dhowells@redhat.com>
(cherry picked from 1b16e7ac850969f38b375e511e3fa2f474a33867 commit)
2006-10-05 15:10:12 +01:00

865 lines
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/*
* Copyright (C) 2001 Anton Blanchard <anton@au.ibm.com>, IBM
* Copyright (C) 2001 Paul Mackerras <paulus@au.ibm.com>, IBM
* Copyright (C) 2004 Benjamin Herrenschmidt <benh@kernel.crashing.org>, IBM Corp.
* Copyright (C) 2004 IBM Corporation
*
* Additional Author(s):
* Ryan S. Arnold <rsa@us.ibm.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#include <linux/console.h>
#include <linux/cpumask.h>
#include <linux/init.h>
#include <linux/kbd_kern.h>
#include <linux/kernel.h>
#include <linux/kobject.h>
#include <linux/kthread.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/major.h>
#include <linux/sysrq.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/sched.h>
#include <linux/spinlock.h>
#include <linux/delay.h>
#include <asm/uaccess.h>
#include "hvc_console.h"
#define HVC_MAJOR 229
#define HVC_MINOR 0
#define TIMEOUT (10)
/*
* Wait this long per iteration while trying to push buffered data to the
* hypervisor before allowing the tty to complete a close operation.
*/
#define HVC_CLOSE_WAIT (HZ/100) /* 1/10 of a second */
/*
* These sizes are most efficient for vio, because they are the
* native transfer size. We could make them selectable in the
* future to better deal with backends that want other buffer sizes.
*/
#define N_OUTBUF 16
#define N_INBUF 16
#define __ALIGNED__ __attribute__((__aligned__(sizeof(long))))
static struct tty_driver *hvc_driver;
static struct task_struct *hvc_task;
/* Picks up late kicks after list walk but before schedule() */
static int hvc_kicked;
#ifdef CONFIG_MAGIC_SYSRQ
static int sysrq_pressed;
#endif
struct hvc_struct {
spinlock_t lock;
int index;
struct tty_struct *tty;
unsigned int count;
int do_wakeup;
char *outbuf;
int outbuf_size;
int n_outbuf;
uint32_t vtermno;
struct hv_ops *ops;
int irq_requested;
int irq;
struct list_head next;
struct kobject kobj; /* ref count & hvc_struct lifetime */
};
/* dynamic list of hvc_struct instances */
static struct list_head hvc_structs = LIST_HEAD_INIT(hvc_structs);
/*
* Protect the list of hvc_struct instances from inserts and removals during
* list traversal.
*/
static DEFINE_SPINLOCK(hvc_structs_lock);
/*
* This value is used to assign a tty->index value to a hvc_struct based
* upon order of exposure via hvc_probe(), when we can not match it to
* a console canidate registered with hvc_instantiate().
*/
static int last_hvc = -1;
/*
* Do not call this function with either the hvc_strucst_lock or the hvc_struct
* lock held. If successful, this function increments the kobject reference
* count against the target hvc_struct so it should be released when finished.
*/
struct hvc_struct *hvc_get_by_index(int index)
{
struct hvc_struct *hp;
unsigned long flags;
spin_lock(&hvc_structs_lock);
list_for_each_entry(hp, &hvc_structs, next) {
spin_lock_irqsave(&hp->lock, flags);
if (hp->index == index) {
kobject_get(&hp->kobj);
spin_unlock_irqrestore(&hp->lock, flags);
spin_unlock(&hvc_structs_lock);
return hp;
}
spin_unlock_irqrestore(&hp->lock, flags);
}
hp = NULL;
spin_unlock(&hvc_structs_lock);
return hp;
}
/*
* Initial console vtermnos for console API usage prior to full console
* initialization. Any vty adapter outside this range will not have usable
* console interfaces but can still be used as a tty device. This has to be
* static because kmalloc will not work during early console init.
*/
static struct hv_ops *cons_ops[MAX_NR_HVC_CONSOLES];
static uint32_t vtermnos[MAX_NR_HVC_CONSOLES] =
{[0 ... MAX_NR_HVC_CONSOLES - 1] = -1};
/*
* Console APIs, NOT TTY. These APIs are available immediately when
* hvc_console_setup() finds adapters.
*/
void hvc_console_print(struct console *co, const char *b, unsigned count)
{
char c[N_OUTBUF] __ALIGNED__;
unsigned i = 0, n = 0;
int r, donecr = 0, index = co->index;
/* Console access attempt outside of acceptable console range. */
if (index >= MAX_NR_HVC_CONSOLES)
return;
/* This console adapter was removed so it is not useable. */
if (vtermnos[index] < 0)
return;
while (count > 0 || i > 0) {
if (count > 0 && i < sizeof(c)) {
if (b[n] == '\n' && !donecr) {
c[i++] = '\r';
donecr = 1;
} else {
c[i++] = b[n++];
donecr = 0;
--count;
}
} else {
r = cons_ops[index]->put_chars(vtermnos[index], c, i);
if (r < 0) {
/* throw away chars on error */
i = 0;
} else if (r > 0) {
i -= r;
if (i > 0)
memmove(c, c+r, i);
}
}
}
}
static struct tty_driver *hvc_console_device(struct console *c, int *index)
{
if (vtermnos[c->index] == -1)
return NULL;
*index = c->index;
return hvc_driver;
}
static int __init hvc_console_setup(struct console *co, char *options)
{
if (co->index < 0 || co->index >= MAX_NR_HVC_CONSOLES)
return -ENODEV;
if (vtermnos[co->index] == -1)
return -ENODEV;
return 0;
}
struct console hvc_con_driver = {
.name = "hvc",
.write = hvc_console_print,
.device = hvc_console_device,
.setup = hvc_console_setup,
.flags = CON_PRINTBUFFER,
.index = -1,
};
/*
* Early console initialization. Preceeds driver initialization.
*
* (1) we are first, and the user specified another driver
* -- index will remain -1
* (2) we are first and the user specified no driver
* -- index will be set to 0, then we will fail setup.
* (3) we are first and the user specified our driver
* -- index will be set to user specified driver, and we will fail
* (4) we are after driver, and this initcall will register us
* -- if the user didn't specify a driver then the console will match
*
* Note that for cases 2 and 3, we will match later when the io driver
* calls hvc_instantiate() and call register again.
*/
static int __init hvc_console_init(void)
{
register_console(&hvc_con_driver);
return 0;
}
console_initcall(hvc_console_init);
/*
* hvc_instantiate() is an early console discovery method which locates
* consoles * prior to the vio subsystem discovering them. Hotplugged
* vty adapters do NOT get an hvc_instantiate() callback since they
* appear after early console init.
*/
int hvc_instantiate(uint32_t vtermno, int index, struct hv_ops *ops)
{
struct hvc_struct *hp;
if (index < 0 || index >= MAX_NR_HVC_CONSOLES)
return -1;
if (vtermnos[index] != -1)
return -1;
/* make sure no no tty has been registerd in this index */
hp = hvc_get_by_index(index);
if (hp) {
kobject_put(&hp->kobj);
return -1;
}
vtermnos[index] = vtermno;
cons_ops[index] = ops;
/* reserve all indices upto and including this index */
if (last_hvc < index)
last_hvc = index;
/* if this index is what the user requested, then register
* now (setup won't fail at this point). It's ok to just
* call register again if previously .setup failed.
*/
if (index == hvc_con_driver.index)
register_console(&hvc_con_driver);
return 0;
}
EXPORT_SYMBOL(hvc_instantiate);
/* Wake the sleeping khvcd */
static void hvc_kick(void)
{
hvc_kicked = 1;
wake_up_process(hvc_task);
}
static int hvc_poll(struct hvc_struct *hp);
/*
* NOTE: This API isn't used if the console adapter doesn't support interrupts.
* In this case the console is poll driven.
*/
static irqreturn_t hvc_handle_interrupt(int irq, void *dev_instance)
{
/* if hvc_poll request a repoll, then kick the hvcd thread */
if (hvc_poll(dev_instance))
hvc_kick();
return IRQ_HANDLED;
}
static void hvc_unthrottle(struct tty_struct *tty)
{
hvc_kick();
}
/*
* The TTY interface won't be used until after the vio layer has exposed the vty
* adapter to the kernel.
*/
static int hvc_open(struct tty_struct *tty, struct file * filp)
{
struct hvc_struct *hp;
unsigned long flags;
int irq = NO_IRQ;
int rc = 0;
struct kobject *kobjp;
/* Auto increments kobject reference if found. */
if (!(hp = hvc_get_by_index(tty->index)))
return -ENODEV;
spin_lock_irqsave(&hp->lock, flags);
/* Check and then increment for fast path open. */
if (hp->count++ > 0) {
spin_unlock_irqrestore(&hp->lock, flags);
hvc_kick();
return 0;
} /* else count == 0 */
tty->driver_data = hp;
tty->low_latency = 1; /* Makes flushes to ldisc synchronous. */
hp->tty = tty;
/* Save for request_irq outside of spin_lock. */
irq = hp->irq;
if (irq != NO_IRQ)
hp->irq_requested = 1;
kobjp = &hp->kobj;
spin_unlock_irqrestore(&hp->lock, flags);
/* check error, fallback to non-irq */
if (irq != NO_IRQ)
rc = request_irq(irq, hvc_handle_interrupt, IRQF_DISABLED, "hvc_console", hp);
/*
* If the request_irq() fails and we return an error. The tty layer
* will call hvc_close() after a failed open but we don't want to clean
* up there so we'll clean up here and clear out the previously set
* tty fields and return the kobject reference.
*/
if (rc) {
spin_lock_irqsave(&hp->lock, flags);
hp->tty = NULL;
hp->irq_requested = 0;
spin_unlock_irqrestore(&hp->lock, flags);
tty->driver_data = NULL;
kobject_put(kobjp);
printk(KERN_ERR "hvc_open: request_irq failed with rc %d.\n", rc);
}
/* Force wakeup of the polling thread */
hvc_kick();
return rc;
}
static void hvc_close(struct tty_struct *tty, struct file * filp)
{
struct hvc_struct *hp;
struct kobject *kobjp;
int irq = NO_IRQ;
unsigned long flags;
if (tty_hung_up_p(filp))
return;
/*
* No driver_data means that this close was issued after a failed
* hvc_open by the tty layer's release_dev() function and we can just
* exit cleanly because the kobject reference wasn't made.
*/
if (!tty->driver_data)
return;
hp = tty->driver_data;
spin_lock_irqsave(&hp->lock, flags);
kobjp = &hp->kobj;
if (--hp->count == 0) {
if (hp->irq_requested)
irq = hp->irq;
hp->irq_requested = 0;
/* We are done with the tty pointer now. */
hp->tty = NULL;
spin_unlock_irqrestore(&hp->lock, flags);
/*
* Chain calls chars_in_buffer() and returns immediately if
* there is no buffered data otherwise sleeps on a wait queue
* waking periodically to check chars_in_buffer().
*/
tty_wait_until_sent(tty, HVC_CLOSE_WAIT);
if (irq != NO_IRQ)
free_irq(irq, hp);
} else {
if (hp->count < 0)
printk(KERN_ERR "hvc_close %X: oops, count is %d\n",
hp->vtermno, hp->count);
spin_unlock_irqrestore(&hp->lock, flags);
}
kobject_put(kobjp);
}
static void hvc_hangup(struct tty_struct *tty)
{
struct hvc_struct *hp = tty->driver_data;
unsigned long flags;
int irq = NO_IRQ;
int temp_open_count;
struct kobject *kobjp;
if (!hp)
return;
spin_lock_irqsave(&hp->lock, flags);
/*
* The N_TTY line discipline has problems such that in a close vs
* open->hangup case this can be called after the final close so prevent
* that from happening for now.
*/
if (hp->count <= 0) {
spin_unlock_irqrestore(&hp->lock, flags);
return;
}
kobjp = &hp->kobj;
temp_open_count = hp->count;
hp->count = 0;
hp->n_outbuf = 0;
hp->tty = NULL;
if (hp->irq_requested)
/* Saved for use outside of spin_lock. */
irq = hp->irq;
hp->irq_requested = 0;
spin_unlock_irqrestore(&hp->lock, flags);
if (irq != NO_IRQ)
free_irq(irq, hp);
while(temp_open_count) {
--temp_open_count;
kobject_put(kobjp);
}
}
/*
* Push buffered characters whether they were just recently buffered or waiting
* on a blocked hypervisor. Call this function with hp->lock held.
*/
static void hvc_push(struct hvc_struct *hp)
{
int n;
n = hp->ops->put_chars(hp->vtermno, hp->outbuf, hp->n_outbuf);
if (n <= 0) {
if (n == 0) {
hp->do_wakeup = 1;
return;
}
/* throw away output on error; this happens when
there is no session connected to the vterm. */
hp->n_outbuf = 0;
} else
hp->n_outbuf -= n;
if (hp->n_outbuf > 0)
memmove(hp->outbuf, hp->outbuf + n, hp->n_outbuf);
else
hp->do_wakeup = 1;
}
static int hvc_write(struct tty_struct *tty, const unsigned char *buf, int count)
{
struct hvc_struct *hp = tty->driver_data;
unsigned long flags;
int rsize, written = 0;
/* This write was probably executed during a tty close. */
if (!hp)
return -EPIPE;
if (hp->count <= 0)
return -EIO;
spin_lock_irqsave(&hp->lock, flags);
/* Push pending writes */
if (hp->n_outbuf > 0)
hvc_push(hp);
while (count > 0 && (rsize = hp->outbuf_size - hp->n_outbuf) > 0) {
if (rsize > count)
rsize = count;
memcpy(hp->outbuf + hp->n_outbuf, buf, rsize);
count -= rsize;
buf += rsize;
hp->n_outbuf += rsize;
written += rsize;
hvc_push(hp);
}
spin_unlock_irqrestore(&hp->lock, flags);
/*
* Racy, but harmless, kick thread if there is still pending data.
*/
if (hp->n_outbuf)
hvc_kick();
return written;
}
/*
* This is actually a contract between the driver and the tty layer outlining
* how much write room the driver can guarentee will be sent OR BUFFERED. This
* driver MUST honor the return value.
*/
static int hvc_write_room(struct tty_struct *tty)
{
struct hvc_struct *hp = tty->driver_data;
if (!hp)
return -1;
return hp->outbuf_size - hp->n_outbuf;
}
static int hvc_chars_in_buffer(struct tty_struct *tty)
{
struct hvc_struct *hp = tty->driver_data;
if (!hp)
return -1;
return hp->n_outbuf;
}
#define HVC_POLL_READ 0x00000001
#define HVC_POLL_WRITE 0x00000002
static int hvc_poll(struct hvc_struct *hp)
{
struct tty_struct *tty;
int i, n, poll_mask = 0;
char buf[N_INBUF] __ALIGNED__;
unsigned long flags;
int read_total = 0;
spin_lock_irqsave(&hp->lock, flags);
/* Push pending writes */
if (hp->n_outbuf > 0)
hvc_push(hp);
/* Reschedule us if still some write pending */
if (hp->n_outbuf > 0)
poll_mask |= HVC_POLL_WRITE;
/* No tty attached, just skip */
tty = hp->tty;
if (tty == NULL)
goto bail;
/* Now check if we can get data (are we throttled ?) */
if (test_bit(TTY_THROTTLED, &tty->flags))
goto throttled;
/* If we aren't interrupt driven and aren't throttled, we always
* request a reschedule
*/
if (hp->irq == NO_IRQ)
poll_mask |= HVC_POLL_READ;
/* Read data if any */
for (;;) {
int count = tty_buffer_request_room(tty, N_INBUF);
/* If flip is full, just reschedule a later read */
if (count == 0) {
poll_mask |= HVC_POLL_READ;
break;
}
n = hp->ops->get_chars(hp->vtermno, buf, count);
if (n <= 0) {
/* Hangup the tty when disconnected from host */
if (n == -EPIPE) {
spin_unlock_irqrestore(&hp->lock, flags);
tty_hangup(tty);
spin_lock_irqsave(&hp->lock, flags);
} else if ( n == -EAGAIN ) {
/*
* Some back-ends can only ensure a certain min
* num of bytes read, which may be > 'count'.
* Let the tty clear the flip buff to make room.
*/
poll_mask |= HVC_POLL_READ;
}
break;
}
for (i = 0; i < n; ++i) {
#ifdef CONFIG_MAGIC_SYSRQ
if (hp->index == hvc_con_driver.index) {
/* Handle the SysRq Hack */
/* XXX should support a sequence */
if (buf[i] == '\x0f') { /* ^O */
sysrq_pressed = 1;
continue;
} else if (sysrq_pressed) {
handle_sysrq(buf[i], tty);
sysrq_pressed = 0;
continue;
}
}
#endif /* CONFIG_MAGIC_SYSRQ */
tty_insert_flip_char(tty, buf[i], 0);
}
read_total += n;
}
throttled:
/* Wakeup write queue if necessary */
if (hp->do_wakeup) {
hp->do_wakeup = 0;
tty_wakeup(tty);
}
bail:
spin_unlock_irqrestore(&hp->lock, flags);
if (read_total)
tty_flip_buffer_push(tty);
return poll_mask;
}
#if defined(CONFIG_XMON) && defined(CONFIG_SMP)
extern cpumask_t cpus_in_xmon;
#else
static const cpumask_t cpus_in_xmon = CPU_MASK_NONE;
#endif
/*
* This kthread is either polling or interrupt driven. This is determined by
* calling hvc_poll() who determines whether a console adapter support
* interrupts.
*/
int khvcd(void *unused)
{
int poll_mask;
struct hvc_struct *hp;
__set_current_state(TASK_RUNNING);
do {
poll_mask = 0;
hvc_kicked = 0;
try_to_freeze();
wmb();
if (cpus_empty(cpus_in_xmon)) {
spin_lock(&hvc_structs_lock);
list_for_each_entry(hp, &hvc_structs, next) {
poll_mask |= hvc_poll(hp);
}
spin_unlock(&hvc_structs_lock);
} else
poll_mask |= HVC_POLL_READ;
if (hvc_kicked)
continue;
if (poll_mask & HVC_POLL_WRITE) {
yield();
continue;
}
set_current_state(TASK_INTERRUPTIBLE);
if (!hvc_kicked) {
if (poll_mask == 0)
schedule();
else
msleep_interruptible(TIMEOUT);
}
__set_current_state(TASK_RUNNING);
} while (!kthread_should_stop());
return 0;
}
static const struct tty_operations hvc_ops = {
.open = hvc_open,
.close = hvc_close,
.write = hvc_write,
.hangup = hvc_hangup,
.unthrottle = hvc_unthrottle,
.write_room = hvc_write_room,
.chars_in_buffer = hvc_chars_in_buffer,
};
/* callback when the kboject ref count reaches zero. */
static void destroy_hvc_struct(struct kobject *kobj)
{
struct hvc_struct *hp = container_of(kobj, struct hvc_struct, kobj);
unsigned long flags;
spin_lock(&hvc_structs_lock);
spin_lock_irqsave(&hp->lock, flags);
list_del(&(hp->next));
spin_unlock_irqrestore(&hp->lock, flags);
spin_unlock(&hvc_structs_lock);
kfree(hp);
}
static struct kobj_type hvc_kobj_type = {
.release = destroy_hvc_struct,
};
struct hvc_struct __devinit *hvc_alloc(uint32_t vtermno, int irq,
struct hv_ops *ops, int outbuf_size)
{
struct hvc_struct *hp;
int i;
hp = kmalloc(ALIGN(sizeof(*hp), sizeof(long)) + outbuf_size,
GFP_KERNEL);
if (!hp)
return ERR_PTR(-ENOMEM);
memset(hp, 0x00, sizeof(*hp));
hp->vtermno = vtermno;
hp->irq = irq;
hp->ops = ops;
hp->outbuf_size = outbuf_size;
hp->outbuf = &((char *)hp)[ALIGN(sizeof(*hp), sizeof(long))];
kobject_init(&hp->kobj);
hp->kobj.ktype = &hvc_kobj_type;
spin_lock_init(&hp->lock);
spin_lock(&hvc_structs_lock);
/*
* find index to use:
* see if this vterm id matches one registered for console.
*/
for (i=0; i < MAX_NR_HVC_CONSOLES; i++)
if (vtermnos[i] == hp->vtermno &&
cons_ops[i] == hp->ops)
break;
/* no matching slot, just use a counter */
if (i >= MAX_NR_HVC_CONSOLES)
i = ++last_hvc;
hp->index = i;
list_add_tail(&(hp->next), &hvc_structs);
spin_unlock(&hvc_structs_lock);
return hp;
}
EXPORT_SYMBOL(hvc_alloc);
int __devexit hvc_remove(struct hvc_struct *hp)
{
unsigned long flags;
struct kobject *kobjp;
struct tty_struct *tty;
spin_lock_irqsave(&hp->lock, flags);
tty = hp->tty;
kobjp = &hp->kobj;
if (hp->index < MAX_NR_HVC_CONSOLES)
vtermnos[hp->index] = -1;
/* Don't whack hp->irq because tty_hangup() will need to free the irq. */
spin_unlock_irqrestore(&hp->lock, flags);
/*
* We 'put' the instance that was grabbed when the kobject instance
* was intialized using kobject_init(). Let the last holder of this
* kobject cause it to be removed, which will probably be the tty_hangup
* below.
*/
kobject_put(kobjp);
/*
* This function call will auto chain call hvc_hangup. The tty should
* always be valid at this time unless a simultaneous tty close already
* cleaned up the hvc_struct.
*/
if (tty)
tty_hangup(tty);
return 0;
}
EXPORT_SYMBOL(hvc_remove);
/* Driver initialization. Follow console initialization. This is where the TTY
* interfaces start to become available. */
int __init hvc_init(void)
{
struct tty_driver *drv;
/* We need more than hvc_count adapters due to hotplug additions. */
drv = alloc_tty_driver(HVC_ALLOC_TTY_ADAPTERS);
if (!drv)
return -ENOMEM;
drv->owner = THIS_MODULE;
drv->driver_name = "hvc";
drv->name = "hvc";
drv->major = HVC_MAJOR;
drv->minor_start = HVC_MINOR;
drv->type = TTY_DRIVER_TYPE_SYSTEM;
drv->init_termios = tty_std_termios;
drv->flags = TTY_DRIVER_REAL_RAW;
tty_set_operations(drv, &hvc_ops);
/* Always start the kthread because there can be hotplug vty adapters
* added later. */
hvc_task = kthread_run(khvcd, NULL, "khvcd");
if (IS_ERR(hvc_task)) {
panic("Couldn't create kthread for console.\n");
put_tty_driver(drv);
return -EIO;
}
if (tty_register_driver(drv))
panic("Couldn't register hvc console driver\n");
mb();
hvc_driver = drv;
return 0;
}
module_init(hvc_init);
/* This isn't particularily necessary due to this being a console driver
* but it is nice to be thorough.
*/
static void __exit hvc_exit(void)
{
kthread_stop(hvc_task);
tty_unregister_driver(hvc_driver);
/* return tty_struct instances allocated in hvc_init(). */
put_tty_driver(hvc_driver);
unregister_console(&hvc_con_driver);
}
module_exit(hvc_exit);
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