tty: The big operations rework

- Operations are now a shared const function block as with most other Linux
  objects

- Introduce wrappers for some optional functions to get consistent behaviour

- Wrap put_char which used to be patched by the tty layer

- Document which functions are needed/optional

- Make put_char report success/fail

- Cache the driver->ops pointer in the tty as tty->ops

- Remove various surplus lock calls we no longer need

- Remove proc_write method as noted by Alexey Dobriyan

- Introduce some missing sanity checks where certain driver/ldisc
  combinations would oops as they didn't check needed methods were present

[akpm@linux-foundation.org: fix fs/compat_ioctl.c build]
[akpm@linux-foundation.org: fix isicom]
[akpm@linux-foundation.org: fix arch/ia64/hp/sim/simserial.c build]
[akpm@linux-foundation.org: fix kgdb]
Signed-off-by: Alan Cox <alan@redhat.com>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de>
Cc: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 30 insertions, 14 deletions

diff --git a/drivers/serial/kgdboc.c b/drivers/serial/kgdboc.c
index 9cf03327386..eadc1ab6bbc 100644
--- a/drivers/serial/kgdboc.c
+++ b/drivers/serial/kgdboc.c
@@ -96,12 +96,14 @@ static void cleanup_kgdboc(void)
 
 static int kgdboc_get_char(void)
 {
-        return kgdb_tty_driver->poll_get_char(kgdb_tty_driver, kgdb_tty_line);
+        return kgdb_tty_driver->ops->poll_get_char(kgdb_tty_driver,
+                                                kgdb_tty_line);
 }
 
 static void kgdboc_put_char(u8 chr)
 {
-        kgdb_tty_driver->poll_put_char(kgdb_tty_driver, kgdb_tty_line, chr);
+        kgdb_tty_driver->ops->poll_put_char(kgdb_tty_driver,
+                                        kgdb_tty_line, chr);
 }
 
 static int param_set_kgdboc_var(const char *kmessage, struct kernel_param *kp)
diff --git a/drivers/serial/serial_core.c b/drivers/serial/serial_core.c
index 6c7a5cf7658..1e2b9d826f6 100644
--- a/drivers/serial/serial_core.c
+++ b/drivers/serial/serial_core.c
@@ -532,15 +532,25 @@ uart_write(struct tty_struct *tty, const unsigned char *buf, int count)
 static int uart_write_room(struct tty_struct *tty)
 {
         struct uart_state *state = tty->driver_data;
+        unsigned long flags;
+        int ret;
 
-        return uart_circ_chars_free(&state->info->xmit);
+        spin_lock_irqsave(&state->port->lock, flags);
+        ret = uart_circ_chars_free(&state->info->xmit);
+        spin_unlock_irqrestore(&state->port->lock, flags);
+        return ret;
 }
 
 static int uart_chars_in_buffer(struct tty_struct *tty)
 {
         struct uart_state *state = tty->driver_data;
+        unsigned long flags;
+        int ret;
 
-        return uart_circ_chars_pending(&state->info->xmit);
+        spin_lock_irqsave(&state->port->lock, flags);
+        ret = uart_circ_chars_pending(&state->info->xmit);
+        spin_unlock_irqrestore(&state->port->lock, flags);
+        return ret;
 }
 
 static void uart_flush_buffer(struct tty_struct *tty)
@@ -622,6 +632,11 @@ static int uart_get_info(struct uart_state *state,
         struct serial_struct tmp;
 
         memset(&tmp, 0, sizeof(tmp));
+
+        /* Ensure the state we copy is consistent and no hardware changes
+           occur as we go */
+        mutex_lock(&state->mutex);
+
         tmp.type            = port->type;
         tmp.line            = port->line;
         tmp.port            = port->iobase;
@@ -641,6 +656,8 @@ static int uart_get_info(struct uart_state *state,
         tmp.iomem_reg_shift = port->regshift;
         tmp.iomem_base      = (void *)(unsigned long)port->mapbase;
 
+        mutex_unlock(&state->mutex);
+
         if (copy_to_user(retinfo, &tmp, sizeof(*retinfo)))
                 return -EFAULT;
         return 0;
@@ -918,14 +935,12 @@ static void uart_break_ctl(struct tty_struct *tty, int break_state)
         struct uart_state *state = tty->driver_data;
         struct uart_port *port = state->port;
 
-        lock_kernel();
         mutex_lock(&state->mutex);
 
         if (port->type != PORT_UNKNOWN)
                 port->ops->break_ctl(port, break_state);
 
         mutex_unlock(&state->mutex);
-        unlock_kernel();
 }
 
 static int uart_do_autoconfig(struct uart_state *state)
@@ -1074,7 +1089,6 @@ uart_ioctl(struct tty_struct *tty, struct file *filp, unsigned int cmd,
         int ret = -ENOIOCTLCMD;
 
 
-        lock_kernel();
         /*
          * These ioctls don't rely on the hardware to be present.
          */
@@ -1144,10 +1158,9 @@ uart_ioctl(struct tty_struct *tty, struct file *filp, unsigned int cmd,
                 break;
         }
         }
- out_up:
+out_up:
         mutex_unlock(&state->mutex);
- out:
-        unlock_kernel();
+out:
         return ret;
 }
 
@@ -1173,7 +1186,6 @@ static void uart_set_termios(struct tty_struct *tty,
                 return;
         }
 
-        lock_kernel();
         uart_change_speed(state, old_termios);
 
         /* Handle transition to B0 status */
@@ -1206,7 +1218,6 @@ static void uart_set_termios(struct tty_struct *tty,
                 }
                 spin_unlock_irqrestore(&state->port->lock, flags);
         }
-        unlock_kernel();
 #if 0
         /*
          * No need to wake up processes in open wait, since they
@@ -1322,11 +1333,11 @@ static void uart_wait_until_sent(struct tty_struct *tty, int timeout)
         struct uart_port *port = state->port;
         unsigned long char_time, expire;
 
-        BUG_ON(!kernel_locked());
-
         if (port->type == PORT_UNKNOWN || port->fifosize == 0)
                 return;
 
+        lock_kernel();
+
         /*
          * Set the check interval to be 1/5 of the estimated time to
          * send a single character, and make it at least 1.  The check
@@ -1372,6 +1383,7 @@ static void uart_wait_until_sent(struct tty_struct *tty, int timeout)
                         break;
         }
         set_current_state(TASK_RUNNING); /* might not be needed */
+        unlock_kernel();
 }
 
 /*
@@ -2085,7 +2097,9 @@ int uart_resume_port(struct uart_driver *drv, struct uart_port *port)
                 int ret;
 
                 uart_change_pm(state, 0);
+                spin_lock_irq(&port->lock);
                 ops->set_mctrl(port, 0);
+                spin_unlock_irq(&port->lock);
                 ret = ops->startup(port);
                 if (ret == 0) {
                         uart_change_speed(state, NULL);