OSCL-LXR linux-6.0.1/​drivers/​tty/​hvc/​hvc_console.c	Source navigation Diff markup Identifier search General search
	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0+
 /*
  * 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>
  */
 
 #include <linux/console.h>
 #include <linux/cpumask.h>
 #include <linux/init.h>
 #include <linux/kbd_kern.h>
 #include <linux/kernel.h>
 #include <linux/kthread.h>
 #include <linux/list.h>
 #include <linux/major.h>
 #include <linux/atomic.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 <linux/freezer.h>
 #include <linux/slab.h>
 #include <linux/serial_core.h>
 
 #include <linux/uaccess.h>
 
 #include "hvc_console.h"
 
 #define HVC_MAJOR   229
 #define HVC_MINOR   0
 
 /*
  * 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__(L1_CACHE_BYTES)))
 
 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;
 
 /* hvc_init is triggered from hvc_alloc, i.e. only when actually used */
 static atomic_t hvc_needs_init __read_mostly = ATOMIC_INIT(-1);
 
 static int hvc_init(void);
 
 #ifdef CONFIG_MAGIC_SYSRQ
 static int sysrq_pressed;
 #endif
 
 /* dynamic list of hvc_struct instances */
 static LIST_HEAD(hvc_structs);
 
 /*
  * Protect the list of hvc_struct instances from inserts and removals during
  * list traversal.
  */
 static DEFINE_MUTEX(hvc_structs_mutex);
 
 /*
  * 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 candidate registered with hvc_instantiate().
  */
 static int last_hvc = -1;
 
 /*
  * Do not call this function with either the hvc_structs_mutex or the hvc_struct
  * lock held.  If successful, this function increments the kref reference
  * count against the target hvc_struct so it should be released when finished.
  */
 static struct hvc_struct *hvc_get_by_index(int index)
 {
     struct hvc_struct *hp;
     unsigned long flags;
 
     mutex_lock(&hvc_structs_mutex);
 
     list_for_each_entry(hp, &hvc_structs, next) {
         spin_lock_irqsave(&hp->lock, flags);
         if (hp->index == index) {
             tty_port_get(&hp->port);
             spin_unlock_irqrestore(&hp->lock, flags);
             mutex_unlock(&hvc_structs_mutex);
             return hp;
         }
         spin_unlock_irqrestore(&hp->lock, flags);
     }
     hp = NULL;
     mutex_unlock(&hvc_structs_mutex);
 
     return hp;
 }
 
 static int __hvc_flush(const struct hv_ops *ops, uint32_t vtermno, bool wait)
 {
     if (wait)
         might_sleep();
 
     if (ops->flush)
         return ops->flush(vtermno, wait);
     return 0;
 }
 
 static int hvc_console_flush(const struct hv_ops *ops, uint32_t vtermno)
 {
     return __hvc_flush(ops, vtermno, false);
 }
 
 /*
  * Wait for the console to flush before writing more to it. This sleeps.
  */
 static int hvc_flush(struct hvc_struct *hp)
 {
     return __hvc_flush(hp->ops, hp->vtermno, true);
 }
 
 /*
  * 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 const 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.
  */
 
 static 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 usable. */
     if (vtermnos[index] == -1)
         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 characters on error
                  * but spin in case of -EAGAIN */
                 if (r != -EAGAIN) {
                     i = 0;
                 } else {
                     hvc_console_flush(cons_ops[index],
                               vtermnos[index]);
                 }
             } else if (r > 0) {
                 i -= r;
                 if (i > 0)
                     memmove(c, c+r, i);
             }
         }
     }
     hvc_console_flush(cons_ops[index], vtermnos[index]);
 }
 
 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 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;
 }
 
 static struct console hvc_console = {
     .name       = "hvc",
     .write      = hvc_console_print,
     .device     = hvc_console_device,
     .setup      = hvc_console_setup,
     .flags      = CON_PRINTBUFFER,
     .index      = -1,
 };
 
 /*
  * Early console initialization.  Precedes 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_console);
     return 0;
 }
 console_initcall(hvc_console_init);
 
 /* callback when the kboject ref count reaches zero. */
 static void hvc_port_destruct(struct tty_port *port)
 {
     struct hvc_struct *hp = container_of(port, struct hvc_struct, port);
     unsigned long flags;
 
     mutex_lock(&hvc_structs_mutex);
 
     spin_lock_irqsave(&hp->lock, flags);
     list_del(&(hp->next));
     spin_unlock_irqrestore(&hp->lock, flags);
 
     mutex_unlock(&hvc_structs_mutex);
 
     kfree(hp);
 }
 
 static void hvc_check_console(int index)
 {
     /* Already enabled, bail out */
     if (hvc_console.flags & CON_ENABLED)
         return;
 
     /* 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_console.index)
         register_console(&hvc_console);
 }
 
 /*
  * 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, const 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 tty has been registered in this index */
     hp = hvc_get_by_index(index);
     if (hp) {
         tty_port_put(&hp->port);
         return -1;
     }
 
     vtermnos[index] = vtermno;
     cons_ops[index] = ops;
 
     /* check if we need to re-register the kernel console */
     hvc_check_console(index);
 
     return 0;
 }
 EXPORT_SYMBOL_GPL(hvc_instantiate);
 
 /* Wake the sleeping khvcd */
 void hvc_kick(void)
 {
     hvc_kicked = 1;
     wake_up_process(hvc_task);
 }
 EXPORT_SYMBOL_GPL(hvc_kick);
 
 static void hvc_unthrottle(struct tty_struct *tty)
 {
     hvc_kick();
 }
 
 static int hvc_install(struct tty_driver *driver, struct tty_struct *tty)
 {
     struct hvc_struct *hp;
     int rc;
 
     /* Auto increments kref reference if found. */
     hp = hvc_get_by_index(tty->index);
     if (!hp)
         return -ENODEV;
 
     tty->driver_data = hp;
 
     rc = tty_port_install(&hp->port, driver, tty);
     if (rc)
         tty_port_put(&hp->port);
     return rc;
 }
 
 /*
  * 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 = tty->driver_data;
     unsigned long flags;
     int rc = 0;
 
     spin_lock_irqsave(&hp->port.lock, flags);
     /* Check and then increment for fast path open. */
     if (hp->port.count++ > 0) {
         spin_unlock_irqrestore(&hp->port.lock, flags);
         hvc_kick();
         return 0;
     } /* else count == 0 */
     spin_unlock_irqrestore(&hp->port.lock, flags);
 
     tty_port_tty_set(&hp->port, tty);
 
     if (hp->ops->notifier_add)
         rc = hp->ops->notifier_add(hp, hp->data);
 
     /*
      * If the notifier fails 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 kref reference.
      */
     if (rc) {
         printk(KERN_ERR "hvc_open: request_irq failed with rc %d.\n", rc);
     } else {
         /* We are ready... raise DTR/RTS */
         if (C_BAUD(tty))
             if (hp->ops->dtr_rts)
                 hp->ops->dtr_rts(hp, 1);
         tty_port_set_initialized(&hp->port, true);
     }
 
     /* 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 = tty->driver_data;
     unsigned long flags;
 
     if (tty_hung_up_p(filp))
         return;
 
     spin_lock_irqsave(&hp->port.lock, flags);
 
     if (--hp->port.count == 0) {
         spin_unlock_irqrestore(&hp->port.lock, flags);
         /* We are done with the tty pointer now. */
         tty_port_tty_set(&hp->port, NULL);
 
         if (!tty_port_initialized(&hp->port))
             return;
 
         if (C_HUPCL(tty))
             if (hp->ops->dtr_rts)
                 hp->ops->dtr_rts(hp, 0);
 
         if (hp->ops->notifier_del)
             hp->ops->notifier_del(hp, hp->data);
 
         /* cancel pending tty resize work */
         cancel_work_sync(&hp->tty_resize);
 
         /*
          * 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);
         tty_port_set_initialized(&hp->port, false);
     } else {
         if (hp->port.count < 0)
             printk(KERN_ERR "hvc_close %X: oops, count is %d\n",
                 hp->vtermno, hp->port.count);
         spin_unlock_irqrestore(&hp->port.lock, flags);
     }
 }
 
 static void hvc_cleanup(struct tty_struct *tty)
 {
     struct hvc_struct *hp = tty->driver_data;
 
     tty_port_put(&hp->port);
 }
 
 static void hvc_hangup(struct tty_struct *tty)
 {
     struct hvc_struct *hp = tty->driver_data;
     unsigned long flags;
 
     if (!hp)
         return;
 
     /* cancel pending tty resize work */
     cancel_work_sync(&hp->tty_resize);
 
     spin_lock_irqsave(&hp->port.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->port.count <= 0) {
         spin_unlock_irqrestore(&hp->port.lock, flags);
         return;
     }
 
     hp->port.count = 0;
     spin_unlock_irqrestore(&hp->port.lock, flags);
     tty_port_tty_set(&hp->port, NULL);
 
     hp->n_outbuf = 0;
 
     if (hp->ops->notifier_hangup)
         hp->ops->notifier_hangup(hp, hp->data);
 }
 
 /*
  * Push buffered characters whether they were just recently buffered or waiting
  * on a blocked hypervisor.  Call this function with hp->lock held.
  */
 static int 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 || n == -EAGAIN) {
             hp->do_wakeup = 1;
             return 0;
         }
         /* 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;
 
     return n;
 }
 
 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;
 
     /* FIXME what's this (unprotected) check for? */
     if (hp->port.count <= 0)
         return -EIO;
 
     while (count > 0) {
         int ret = 0;
 
         spin_lock_irqsave(&hp->lock, flags);
 
         rsize = hp->outbuf_size - hp->n_outbuf;
 
         if (rsize) {
             if (rsize > count)
                 rsize = count;
             memcpy(hp->outbuf + hp->n_outbuf, buf, rsize);
             count -= rsize;
             buf += rsize;
             hp->n_outbuf += rsize;
             written += rsize;
         }
 
         if (hp->n_outbuf > 0)
             ret = hvc_push(hp);
 
         spin_unlock_irqrestore(&hp->lock, flags);
 
         if (!ret)
             break;
 
         if (count) {
             if (hp->n_outbuf > 0)
                 hvc_flush(hp);
             cond_resched();
         }
     }
 
     /*
      * Racy, but harmless, kick thread if there is still pending data.
      */
     if (hp->n_outbuf)
         hvc_kick();
 
     return written;
 }
 
 /**
  * hvc_set_winsz() - Resize the hvc tty terminal window.
  * @work:   work structure.
  *
  * The routine shall not be called within an atomic context because it
  * might sleep.
  *
  * Locking: hp->lock
  */
 static void hvc_set_winsz(struct work_struct *work)
 {
     struct hvc_struct *hp;
     unsigned long hvc_flags;
     struct tty_struct *tty;
     struct winsize ws;
 
     hp = container_of(work, struct hvc_struct, tty_resize);
 
     tty = tty_port_tty_get(&hp->port);
     if (!tty)
         return;
 
     spin_lock_irqsave(&hp->lock, hvc_flags);
     ws = hp->ws;
     spin_unlock_irqrestore(&hp->lock, hvc_flags);
 
     tty_do_resize(tty, &ws);
     tty_kref_put(tty);
 }
 
 /*
  * This is actually a contract between the driver and the tty layer outlining
  * how much write room the driver can guarantee will be sent OR BUFFERED.  This
  * driver MUST honor the return value.
  */
 static unsigned int hvc_write_room(struct tty_struct *tty)
 {
     struct hvc_struct *hp = tty->driver_data;
 
     if (!hp)
         return 0;
 
     return hp->outbuf_size - hp->n_outbuf;
 }
 
 static unsigned int hvc_chars_in_buffer(struct tty_struct *tty)
 {
     struct hvc_struct *hp = tty->driver_data;
 
     if (!hp)
         return 0;
     return hp->n_outbuf;
 }
 
 /*
  * timeout will vary between the MIN and MAX values defined here.  By default
  * and during console activity we will use a default MIN_TIMEOUT of 10.  When
  * the console is idle, we increase the timeout value on each pass through
  * msleep until we reach the max.  This may be noticeable as a brief (average
  * one second) delay on the console before the console responds to input when
  * there has been no input for some time.
  */
 #define MIN_TIMEOUT     (10)
 #define MAX_TIMEOUT     (2000)
 static u32 timeout = MIN_TIMEOUT;
 
 /*
  * Maximum number of bytes to get from the console driver if hvc_poll is
  * called from driver (and can't sleep). Any more than this and we break
  * and start polling with khvcd. This value was derived from an OpenBMC
  * console with the OPAL driver that results in about 0.25ms interrupts off
  * latency.
  */
 #define HVC_ATOMIC_READ_MAX 128
 
 #define HVC_POLL_READ   0x00000001
 #define HVC_POLL_WRITE  0x00000002
 
 static int __hvc_poll(struct hvc_struct *hp, bool may_sleep)
 {
     struct tty_struct *tty;
     int i, n, count, poll_mask = 0;
     char buf[N_INBUF] __ALIGNED__;
     unsigned long flags;
     int read_total = 0;
     int written_total = 0;
 
     spin_lock_irqsave(&hp->lock, flags);
 
     /* Push pending writes */
     if (hp->n_outbuf > 0)
         written_total = hvc_push(hp);
 
     /* Reschedule us if still some write pending */
     if (hp->n_outbuf > 0) {
         poll_mask |= HVC_POLL_WRITE;
         /* If hvc_push() was not able to write, sleep a few msecs */
         timeout = (written_total) ? 0 : MIN_TIMEOUT;
     }
 
     if (may_sleep) {
         spin_unlock_irqrestore(&hp->lock, flags);
         cond_resched();
         spin_lock_irqsave(&hp->lock, flags);
     }
 
     /* No tty attached, just skip */
     tty = tty_port_tty_get(&hp->port);
     if (tty == NULL)
         goto bail;
 
     /* Now check if we can get data (are we throttled ?) */
     if (tty_throttled(tty))
         goto out;
 
     /* If we aren't notifier driven and aren't throttled, we always
      * request a reschedule
      */
     if (!hp->irq_requested)
         poll_mask |= HVC_POLL_READ;
 
  read_again:
     /* Read data if any */
     count = tty_buffer_request_room(&hp->port, N_INBUF);
 
     /* If flip is full, just reschedule a later read */
     if (count == 0) {
         poll_mask |= HVC_POLL_READ;
         goto out;
     }
 
     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;
         }
         goto out;
     }
 
     for (i = 0; i < n; ++i) {
 #ifdef CONFIG_MAGIC_SYSRQ
         if (hp->index == hvc_console.index) {
             /* Handle the SysRq Hack */
             /* XXX should support a sequence */
             if (buf[i] == '\x0f') { /* ^O */
                 /* if ^O is pressed again, reset
                  * sysrq_pressed and flip ^O char */
                 sysrq_pressed = !sysrq_pressed;
                 if (sysrq_pressed)
                     continue;
             } else if (sysrq_pressed) {
                 handle_sysrq(buf[i]);
                 sysrq_pressed = 0;
                 continue;
             }
         }
 #endif /* CONFIG_MAGIC_SYSRQ */
         tty_insert_flip_char(&hp->port, buf[i], 0);
     }
     read_total += n;
 
     if (may_sleep) {
         /* Keep going until the flip is full */
         spin_unlock_irqrestore(&hp->lock, flags);
         cond_resched();
         spin_lock_irqsave(&hp->lock, flags);
         goto read_again;
     } else if (read_total < HVC_ATOMIC_READ_MAX) {
         /* Break and defer if it's a large read in atomic */
         goto read_again;
     }
 
     /*
      * Latency break, schedule another poll immediately.
      */
     poll_mask |= HVC_POLL_READ;
 
  out:
     /* 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) {
         /* Activity is occurring, so reset the polling backoff value to
            a minimum for performance. */
         timeout = MIN_TIMEOUT;
 
         tty_flip_buffer_push(&hp->port);
     }
     tty_kref_put(tty);
 
     return poll_mask;
 }
 
 int hvc_poll(struct hvc_struct *hp)
 {
     return __hvc_poll(hp, false);
 }
 EXPORT_SYMBOL_GPL(hvc_poll);
 
 /**
  * __hvc_resize() - Update terminal window size information.
  * @hp:     HVC console pointer
  * @ws:     Terminal window size structure
  *
  * Stores the specified window size information in the hvc structure of @hp.
  * The function schedule the tty resize update.
  *
  * Locking: Locking free; the function MUST be called holding hp->lock
  */
 void __hvc_resize(struct hvc_struct *hp, struct winsize ws)
 {
     hp->ws = ws;
     schedule_work(&hp->tty_resize);
 }
 EXPORT_SYMBOL_GPL(__hvc_resize);
 
 /*
  * This kthread is either polling or interrupt driven.  This is determined by
  * calling hvc_poll() who determines whether a console adapter support
  * interrupts.
  */
 static int khvcd(void *unused)
 {
     int poll_mask;
     struct hvc_struct *hp;
 
     set_freezable();
     do {
         poll_mask = 0;
         hvc_kicked = 0;
         try_to_freeze();
         wmb();
         if (!cpus_are_in_xmon()) {
             mutex_lock(&hvc_structs_mutex);
             list_for_each_entry(hp, &hvc_structs, next) {
                 poll_mask |= __hvc_poll(hp, true);
                 cond_resched();
             }
             mutex_unlock(&hvc_structs_mutex);
         } else
             poll_mask |= HVC_POLL_READ;
         if (hvc_kicked)
             continue;
         set_current_state(TASK_INTERRUPTIBLE);
         if (!hvc_kicked) {
             if (poll_mask == 0)
                 schedule();
             else {
                 unsigned long j_timeout;
 
                 if (timeout < MAX_TIMEOUT)
                     timeout += (timeout >> 6) + 1;
 
                 /*
                  * We don't use msleep_interruptible otherwise
                  * "kick" will fail to wake us up
                  */
                 j_timeout = msecs_to_jiffies(timeout) + 1;
                 schedule_timeout_interruptible(j_timeout);
             }
         }
         __set_current_state(TASK_RUNNING);
     } while (!kthread_should_stop());
 
     return 0;
 }
 
 static int hvc_tiocmget(struct tty_struct *tty)
 {
     struct hvc_struct *hp = tty->driver_data;
 
     if (!hp || !hp->ops->tiocmget)
         return -EINVAL;
     return hp->ops->tiocmget(hp);
 }
 
 static int hvc_tiocmset(struct tty_struct *tty,
             unsigned int set, unsigned int clear)
 {
     struct hvc_struct *hp = tty->driver_data;
 
     if (!hp || !hp->ops->tiocmset)
         return -EINVAL;
     return hp->ops->tiocmset(hp, set, clear);
 }
 
 #ifdef CONFIG_CONSOLE_POLL
 static int hvc_poll_init(struct tty_driver *driver, int line, char *options)
 {
     return 0;
 }
 
 static int hvc_poll_get_char(struct tty_driver *driver, int line)
 {
     struct tty_struct *tty = driver->ttys[0];
     struct hvc_struct *hp = tty->driver_data;
     int n;
     char ch;
 
     n = hp->ops->get_chars(hp->vtermno, &ch, 1);
 
     if (n <= 0)
         return NO_POLL_CHAR;
 
     return ch;
 }
 
 static void hvc_poll_put_char(struct tty_driver *driver, int line, char ch)
 {
     struct tty_struct *tty = driver->ttys[0];
     struct hvc_struct *hp = tty->driver_data;
     int n;
 
     do {
         n = hp->ops->put_chars(hp->vtermno, &ch, 1);
     } while (n <= 0);
 }
 #endif
 
 static const struct tty_operations hvc_ops = {
     .install = hvc_install,
     .open = hvc_open,
     .close = hvc_close,
     .cleanup = hvc_cleanup,
     .write = hvc_write,
     .hangup = hvc_hangup,
     .unthrottle = hvc_unthrottle,
     .write_room = hvc_write_room,
     .chars_in_buffer = hvc_chars_in_buffer,
     .tiocmget = hvc_tiocmget,
     .tiocmset = hvc_tiocmset,
 #ifdef CONFIG_CONSOLE_POLL
     .poll_init = hvc_poll_init,
     .poll_get_char = hvc_poll_get_char,
     .poll_put_char = hvc_poll_put_char,
 #endif
 };
 
 static const struct tty_port_operations hvc_port_ops = {
     .destruct = hvc_port_destruct,
 };
 
 struct hvc_struct *hvc_alloc(uint32_t vtermno, int data,
                  const struct hv_ops *ops,
                  int outbuf_size)
 {
     struct hvc_struct *hp;
     int i;
 
     /* We wait until a driver actually comes along */
     if (atomic_inc_not_zero(&hvc_needs_init)) {
         int err = hvc_init();
         if (err)
             return ERR_PTR(err);
     }
 
     hp = kzalloc(ALIGN(sizeof(*hp), sizeof(long)) + outbuf_size,
             GFP_KERNEL);
     if (!hp)
         return ERR_PTR(-ENOMEM);
 
     hp->vtermno = vtermno;
     hp->data = data;
     hp->ops = ops;
     hp->outbuf_size = outbuf_size;
     hp->outbuf = &((char *)hp)[ALIGN(sizeof(*hp), sizeof(long))];
 
     tty_port_init(&hp->port);
     hp->port.ops = &hvc_port_ops;
 
     INIT_WORK(&hp->tty_resize, hvc_set_winsz);
     spin_lock_init(&hp->lock);
     mutex_lock(&hvc_structs_mutex);
 
     /*
      * 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;
 
     if (i >= MAX_NR_HVC_CONSOLES) {
 
         /* find 'empty' slot for console */
         for (i = 0; i < MAX_NR_HVC_CONSOLES && vtermnos[i] != -1; i++) {
         }
 
         /* no matching slot, just use a counter */
         if (i == MAX_NR_HVC_CONSOLES)
             i = ++last_hvc + MAX_NR_HVC_CONSOLES;
     }
 
     hp->index = i;
     if (i < MAX_NR_HVC_CONSOLES) {
         cons_ops[i] = ops;
         vtermnos[i] = vtermno;
     }
 
     list_add_tail(&(hp->next), &hvc_structs);
     mutex_unlock(&hvc_structs_mutex);
 
     /* check if we need to re-register the kernel console */
     hvc_check_console(i);
 
     return hp;
 }
 EXPORT_SYMBOL_GPL(hvc_alloc);
 
 int hvc_remove(struct hvc_struct *hp)
 {
     unsigned long flags;
     struct tty_struct *tty;
 
     tty = tty_port_tty_get(&hp->port);
 
     console_lock();
     spin_lock_irqsave(&hp->lock, flags);
     if (hp->index < MAX_NR_HVC_CONSOLES) {
         vtermnos[hp->index] = -1;
         cons_ops[hp->index] = NULL;
     }
 
     /* Don't whack hp->irq because tty_hangup() will need to free the irq. */
 
     spin_unlock_irqrestore(&hp->lock, flags);
     console_unlock();
 
     /*
      * We 'put' the instance that was grabbed when the kref instance
      * was initialized using kref_init().  Let the last holder of this
      * kref cause it to be removed, which will probably be the tty_vhangup
      * below.
      */
     tty_port_put(&hp->port);
 
     /*
      * This function call will auto chain call hvc_hangup.
      */
     if (tty) {
         tty_vhangup(tty);
         tty_kref_put(tty);
     }
     return 0;
 }
 EXPORT_SYMBOL_GPL(hvc_remove);
 
 /* Driver initialization: called as soon as someone uses hvc_alloc(). */
 static int hvc_init(void)
 {
     struct tty_driver *drv;
     int err;
 
     /* We need more than hvc_count adapters due to hotplug additions. */
     drv = tty_alloc_driver(HVC_ALLOC_TTY_ADAPTERS, TTY_DRIVER_REAL_RAW |
             TTY_DRIVER_RESET_TERMIOS);
     if (IS_ERR(drv)) {
         err = PTR_ERR(drv);
         goto out;
     }
 
     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;
     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)) {
         printk(KERN_ERR "Couldn't create kthread for console.\n");
         err = PTR_ERR(hvc_task);
         goto put_tty;
     }
 
     err = tty_register_driver(drv);
     if (err) {
         printk(KERN_ERR "Couldn't register hvc console driver\n");
         goto stop_thread;
     }
 
     /*
      * Make sure tty is fully registered before allowing it to be
      * found by hvc_console_device.
      */
     smp_mb();
     hvc_driver = drv;
     return 0;
 
 stop_thread:
     kthread_stop(hvc_task);
     hvc_task = NULL;
 put_tty:
     tty_driver_kref_put(drv);
 out:
     return err;
 }

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