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