TTY: create drivers/tty and move the tty core files there

The tty code should be in its own subdirectory and not in the char
driver with all of the cruft that is currently there.

Based on work done by Arnd Bergmann <arnd@arndb.de>

Acked-by: Arnd Bergmann <arnd@arndb.de>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 524 insertions, 0 deletions

diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c
new file mode 100644
index 000000000000..cc1e9850d655
--- /dev/null
+++ b/drivers/tty/tty_buffer.c
@@ -0,0 +1,524 @@
+/*
+ * Tty buffer allocation management
+ */
+
+#include <linux/types.h>
+#include <linux/errno.h>
+#include <linux/tty.h>
+#include <linux/tty_driver.h>
+#include <linux/tty_flip.h>
+#include <linux/timer.h>
+#include <linux/string.h>
+#include <linux/slab.h>
+#include <linux/sched.h>
+#include <linux/init.h>
+#include <linux/wait.h>
+#include <linux/bitops.h>
+#include <linux/delay.h>
+#include <linux/module.h>
+
+/**
+ *      tty_buffer_free_all             -       free buffers used by a tty
+ *      @tty: tty to free from
+ *
+ *      Remove all the buffers pending on a tty whether queued with data
+ *      or in the free ring. Must be called when the tty is no longer in use
+ *
+ *      Locking: none
+ */
+
+void tty_buffer_free_all(struct tty_struct *tty)
+{
+        struct tty_buffer *thead;
+        while ((thead = tty->buf.head) != NULL) {
+                tty->buf.head = thead->next;
+                kfree(thead);
+        }
+        while ((thead = tty->buf.free) != NULL) {
+                tty->buf.free = thead->next;
+                kfree(thead);
+        }
+        tty->buf.tail = NULL;
+        tty->buf.memory_used = 0;
+}
+
+/**
+ *      tty_buffer_alloc        -       allocate a tty buffer
+ *      @tty: tty device
+ *      @size: desired size (characters)
+ *
+ *      Allocate a new tty buffer to hold the desired number of characters.
+ *      Return NULL if out of memory or the allocation would exceed the
+ *      per device queue
+ *
+ *      Locking: Caller must hold tty->buf.lock
+ */
+
+static struct tty_buffer *tty_buffer_alloc(struct tty_struct *tty, size_t size)
+{
+        struct tty_buffer *p;
+
+        if (tty->buf.memory_used + size > 65536)
+                return NULL;
+        p = kmalloc(sizeof(struct tty_buffer) + 2 * size, GFP_ATOMIC);
+        if (p == NULL)
+                return NULL;
+        p->used = 0;
+        p->size = size;
+        p->next = NULL;
+        p->commit = 0;
+        p->read = 0;
+        p->char_buf_ptr = (char *)(p->data);
+        p->flag_buf_ptr = (unsigned char *)p->char_buf_ptr + size;
+        tty->buf.memory_used += size;
+        return p;
+}
+
+/**
+ *      tty_buffer_free         -       free a tty buffer
+ *      @tty: tty owning the buffer
+ *      @b: the buffer to free
+ *
+ *      Free a tty buffer, or add it to the free list according to our
+ *      internal strategy
+ *
+ *      Locking: Caller must hold tty->buf.lock
+ */
+
+static void tty_buffer_free(struct tty_struct *tty, struct tty_buffer *b)
+{
+        /* Dumb strategy for now - should keep some stats */
+        tty->buf.memory_used -= b->size;
+        WARN_ON(tty->buf.memory_used < 0);
+
+        if (b->size >= 512)
+                kfree(b);
+        else {
+                b->next = tty->buf.free;
+                tty->buf.free = b;
+        }
+}
+
+/**
+ *      __tty_buffer_flush              -       flush full tty buffers
+ *      @tty: tty to flush
+ *
+ *      flush all the buffers containing receive data. Caller must
+ *      hold the buffer lock and must have ensured no parallel flush to
+ *      ldisc is running.
+ *
+ *      Locking: Caller must hold tty->buf.lock
+ */
+
+static void __tty_buffer_flush(struct tty_struct *tty)
+{
+        struct tty_buffer *thead;
+
+        while ((thead = tty->buf.head) != NULL) {
+                tty->buf.head = thead->next;
+                tty_buffer_free(tty, thead);
+        }
+        tty->buf.tail = NULL;
+}
+
+/**
+ *      tty_buffer_flush                -       flush full tty buffers
+ *      @tty: tty to flush
+ *
+ *      flush all the buffers containing receive data. If the buffer is
+ *      being processed by flush_to_ldisc then we defer the processing
+ *      to that function
+ *
+ *      Locking: none
+ */
+
+void tty_buffer_flush(struct tty_struct *tty)
+{
+        unsigned long flags;
+        spin_lock_irqsave(&tty->buf.lock, flags);
+
+        /* If the data is being pushed to the tty layer then we can't
+           process it here. Instead set a flag and the flush_to_ldisc
+           path will process the flush request before it exits */
+        if (test_bit(TTY_FLUSHING, &tty->flags)) {
+                set_bit(TTY_FLUSHPENDING, &tty->flags);
+                spin_unlock_irqrestore(&tty->buf.lock, flags);
+                wait_event(tty->read_wait,
+                                test_bit(TTY_FLUSHPENDING, &tty->flags) == 0);
+                return;
+        } else
+                __tty_buffer_flush(tty);
+        spin_unlock_irqrestore(&tty->buf.lock, flags);
+}
+
+/**
+ *      tty_buffer_find         -       find a free tty buffer
+ *      @tty: tty owning the buffer
+ *      @size: characters wanted
+ *
+ *      Locate an existing suitable tty buffer or if we are lacking one then
+ *      allocate a new one. We round our buffers off in 256 character chunks
+ *      to get better allocation behaviour.
+ *
+ *      Locking: Caller must hold tty->buf.lock
+ */
+
+static struct tty_buffer *tty_buffer_find(struct tty_struct *tty, size_t size)
+{
+        struct tty_buffer **tbh = &tty->buf.free;
+        while ((*tbh) != NULL) {
+                struct tty_buffer *t = *tbh;
+                if (t->size >= size) {
+                        *tbh = t->next;
+                        t->next = NULL;
+                        t->used = 0;
+                        t->commit = 0;
+                        t->read = 0;
+                        tty->buf.memory_used += t->size;
+                        return t;
+                }
+                tbh = &((*tbh)->next);
+        }
+        /* Round the buffer size out */
+        size = (size + 0xFF) & ~0xFF;
+        return tty_buffer_alloc(tty, size);
+        /* Should possibly check if this fails for the largest buffer we
+           have queued and recycle that ? */
+}
+
+/**
+ *      tty_buffer_request_room         -       grow tty buffer if needed
+ *      @tty: tty structure
+ *      @size: size desired
+ *
+ *      Make at least size bytes of linear space available for the tty
+ *      buffer. If we fail return the size we managed to find.
+ *
+ *      Locking: Takes tty->buf.lock
+ */
+int tty_buffer_request_room(struct tty_struct *tty, size_t size)
+{
+        struct tty_buffer *b, *n;
+        int left;
+        unsigned long flags;
+
+        spin_lock_irqsave(&tty->buf.lock, flags);
+
+        /* OPTIMISATION: We could keep a per tty "zero" sized buffer to
+           remove this conditional if its worth it. This would be invisible
+           to the callers */
+        if ((b = tty->buf.tail) != NULL)
+                left = b->size - b->used;
+        else
+                left = 0;
+
+        if (left < size) {
+                /* This is the slow path - looking for new buffers to use */
+                if ((n = tty_buffer_find(tty, size)) != NULL) {
+                        if (b != NULL) {
+                                b->next = n;
+                                b->commit = b->used;
+                        } else
+                                tty->buf.head = n;
+                        tty->buf.tail = n;
+                } else
+                        size = left;
+        }
+
+        spin_unlock_irqrestore(&tty->buf.lock, flags);
+        return size;
+}
+EXPORT_SYMBOL_GPL(tty_buffer_request_room);
+
+/**
+ *      tty_insert_flip_string_fixed_flag - Add characters to the tty buffer
+ *      @tty: tty structure
+ *      @chars: characters
+ *      @flag: flag value for each character
+ *      @size: size
+ *
+ *      Queue a series of bytes to the tty buffering. All the characters
+ *      passed are marked with the supplied flag. Returns the number added.
+ *
+ *      Locking: Called functions may take tty->buf.lock
+ */
+
+int tty_insert_flip_string_fixed_flag(struct tty_struct *tty,
+                const unsigned char *chars, char flag, size_t size)
+{
+        int copied = 0;
+        do {
+                int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE);
+                int space = tty_buffer_request_room(tty, goal);
+                struct tty_buffer *tb = tty->buf.tail;
+                /* If there is no space then tb may be NULL */
+                if (unlikely(space == 0))
+                        break;
+                memcpy(tb->char_buf_ptr + tb->used, chars, space);
+                memset(tb->flag_buf_ptr + tb->used, flag, space);
+                tb->used += space;
+                copied += space;
+                chars += space;
+                /* There is a small chance that we need to split the data over
+                   several buffers. If this is the case we must loop */
+        } while (unlikely(size > copied));
+        return copied;
+}
+EXPORT_SYMBOL(tty_insert_flip_string_fixed_flag);
+
+/**
+ *      tty_insert_flip_string_flags    -       Add characters to the tty buffer
+ *      @tty: tty structure
+ *      @chars: characters
+ *      @flags: flag bytes
+ *      @size: size
+ *
+ *      Queue a series of bytes to the tty buffering. For each character
+ *      the flags array indicates the status of the character. Returns the
+ *      number added.
+ *
+ *      Locking: Called functions may take tty->buf.lock
+ */
+
+int tty_insert_flip_string_flags(struct tty_struct *tty,
+                const unsigned char *chars, const char *flags, size_t size)
+{
+        int copied = 0;
+        do {
+                int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE);
+                int space = tty_buffer_request_room(tty, goal);
+                struct tty_buffer *tb = tty->buf.tail;
+                /* If there is no space then tb may be NULL */
+                if (unlikely(space == 0))
+                        break;
+                memcpy(tb->char_buf_ptr + tb->used, chars, space);
+                memcpy(tb->flag_buf_ptr + tb->used, flags, space);
+                tb->used += space;
+                copied += space;
+                chars += space;
+                flags += space;
+                /* There is a small chance that we need to split the data over
+                   several buffers. If this is the case we must loop */
+        } while (unlikely(size > copied));
+        return copied;
+}
+EXPORT_SYMBOL(tty_insert_flip_string_flags);
+
+/**
+ *      tty_schedule_flip       -       push characters to ldisc
+ *      @tty: tty to push from
+ *
+ *      Takes any pending buffers and transfers their ownership to the
+ *      ldisc side of the queue. It then schedules those characters for
+ *      processing by the line discipline.
+ *
+ *      Locking: Takes tty->buf.lock
+ */
+
+void tty_schedule_flip(struct tty_struct *tty)
+{
+        unsigned long flags;
+        spin_lock_irqsave(&tty->buf.lock, flags);
+        if (tty->buf.tail != NULL)
+                tty->buf.tail->commit = tty->buf.tail->used;
+        spin_unlock_irqrestore(&tty->buf.lock, flags);
+        schedule_delayed_work(&tty->buf.work, 1);
+}
+EXPORT_SYMBOL(tty_schedule_flip);
+
+/**
+ *      tty_prepare_flip_string         -       make room for characters
+ *      @tty: tty
+ *      @chars: return pointer for character write area
+ *      @size: desired size
+ *
+ *      Prepare a block of space in the buffer for data. Returns the length
+ *      available and buffer pointer to the space which is now allocated and
+ *      accounted for as ready for normal characters. This is used for drivers
+ *      that need their own block copy routines into the buffer. There is no
+ *      guarantee the buffer is a DMA target!
+ *
+ *      Locking: May call functions taking tty->buf.lock
+ */
+
+int tty_prepare_flip_string(struct tty_struct *tty, unsigned char **chars,
+                                                                size_t size)
+{
+        int space = tty_buffer_request_room(tty, size);
+        if (likely(space)) {
+                struct tty_buffer *tb = tty->buf.tail;
+                *chars = tb->char_buf_ptr + tb->used;
+                memset(tb->flag_buf_ptr + tb->used, TTY_NORMAL, space);
+                tb->used += space;
+        }
+        return space;
+}
+EXPORT_SYMBOL_GPL(tty_prepare_flip_string);
+
+/**
+ *      tty_prepare_flip_string_flags   -       make room for characters
+ *      @tty: tty
+ *      @chars: return pointer for character write area
+ *      @flags: return pointer for status flag write area
+ *      @size: desired size
+ *
+ *      Prepare a block of space in the buffer for data. Returns the length
+ *      available and buffer pointer to the space which is now allocated and
+ *      accounted for as ready for characters. This is used for drivers
+ *      that need their own block copy routines into the buffer. There is no
+ *      guarantee the buffer is a DMA target!
+ *
+ *      Locking: May call functions taking tty->buf.lock
+ */
+
+int tty_prepare_flip_string_flags(struct tty_struct *tty,
+                        unsigned char **chars, char **flags, size_t size)
+{
+        int space = tty_buffer_request_room(tty, size);
+        if (likely(space)) {
+                struct tty_buffer *tb = tty->buf.tail;
+                *chars = tb->char_buf_ptr + tb->used;
+                *flags = tb->flag_buf_ptr + tb->used;
+                tb->used += space;
+        }
+        return space;
+}
+EXPORT_SYMBOL_GPL(tty_prepare_flip_string_flags);
+
+
+
+/**
+ *      flush_to_ldisc
+ *      @work: tty structure passed from work queue.
+ *
+ *      This routine is called out of the software interrupt to flush data
+ *      from the buffer chain to the line discipline.
+ *
+ *      Locking: holds tty->buf.lock to guard buffer list. Drops the lock
+ *      while invoking the line discipline receive_buf method. The
+ *      receive_buf method is single threaded for each tty instance.
+ */
+
+static void flush_to_ldisc(struct work_struct *work)
+{
+        struct tty_struct *tty =
+                container_of(work, struct tty_struct, buf.work.work);
+        unsigned long   flags;
+        struct tty_ldisc *disc;
+
+        disc = tty_ldisc_ref(tty);
+        if (disc == NULL)       /*  !TTY_LDISC */
+                return;
+
+        spin_lock_irqsave(&tty->buf.lock, flags);
+
+        if (!test_and_set_bit(TTY_FLUSHING, &tty->flags)) {
+                struct tty_buffer *head;
+                while ((head = tty->buf.head) != NULL) {
+                        int count;
+                        char *char_buf;
+                        unsigned char *flag_buf;
+
+                        count = head->commit - head->read;
+                        if (!count) {
+                                if (head->next == NULL)
+                                        break;
+                                tty->buf.head = head->next;
+                                tty_buffer_free(tty, head);
+                                continue;
+                        }
+                        /* Ldisc or user is trying to flush the buffers
+                           we are feeding to the ldisc, stop feeding the
+                           line discipline as we want to empty the queue */
+                        if (test_bit(TTY_FLUSHPENDING, &tty->flags))
+                                break;
+                        if (!tty->receive_room) {
+                                schedule_delayed_work(&tty->buf.work, 1);
+                                break;
+                        }
+                        if (count > tty->receive_room)
+                                count = tty->receive_room;
+                        char_buf = head->char_buf_ptr + head->read;
+                        flag_buf = head->flag_buf_ptr + head->read;
+                        head->read += count;
+                        spin_unlock_irqrestore(&tty->buf.lock, flags);
+                        disc->ops->receive_buf(tty, char_buf,
+                                                        flag_buf, count);
+                        spin_lock_irqsave(&tty->buf.lock, flags);
+                }
+                clear_bit(TTY_FLUSHING, &tty->flags);
+        }
+
+        /* We may have a deferred request to flush the input buffer,
+           if so pull the chain under the lock and empty the queue */
+        if (test_bit(TTY_FLUSHPENDING, &tty->flags)) {
+                __tty_buffer_flush(tty);
+                clear_bit(TTY_FLUSHPENDING, &tty->flags);
+                wake_up(&tty->read_wait);
+        }
+        spin_unlock_irqrestore(&tty->buf.lock, flags);
+
+        tty_ldisc_deref(disc);
+}
+
+/**
+ *      tty_flush_to_ldisc
+ *      @tty: tty to push
+ *
+ *      Push the terminal flip buffers to the line discipline.
+ *
+ *      Must not be called from IRQ context.
+ */
+void tty_flush_to_ldisc(struct tty_struct *tty)
+{
+        flush_delayed_work(&tty->buf.work);
+}
+
+/**
+ *      tty_flip_buffer_push    -       terminal
+ *      @tty: tty to push
+ *
+ *      Queue a push of the terminal flip buffers to the line discipline. This
+ *      function must not be called from IRQ context if tty->low_latency is set.
+ *
+ *      In the event of the queue being busy for flipping the work will be
+ *      held off and retried later.
+ *
+ *      Locking: tty buffer lock. Driver locks in low latency mode.
+ */
+
+void tty_flip_buffer_push(struct tty_struct *tty)
+{
+        unsigned long flags;
+        spin_lock_irqsave(&tty->buf.lock, flags);
+        if (tty->buf.tail != NULL)
+                tty->buf.tail->commit = tty->buf.tail->used;
+        spin_unlock_irqrestore(&tty->buf.lock, flags);
+
+        if (tty->low_latency)
+                flush_to_ldisc(&tty->buf.work.work);
+        else
+                schedule_delayed_work(&tty->buf.work, 1);
+}
+EXPORT_SYMBOL(tty_flip_buffer_push);
+
+/**
+ *      tty_buffer_init         -       prepare a tty buffer structure
+ *      @tty: tty to initialise
+ *
+ *      Set up the initial state of the buffer management for a tty device.
+ *      Must be called before the other tty buffer functions are used.
+ *
+ *      Locking: none
+ */
+
+void tty_buffer_init(struct tty_struct *tty)
+{
+        spin_lock_init(&tty->buf.lock);
+        tty->buf.head = NULL;
+        tty->buf.tail = NULL;
+        tty->buf.free = NULL;
+        tty->buf.memory_used = 0;
+        INIT_DELAYED_WORK(&tty->buf.work, flush_to_ldisc);
+}
+