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path: root/drivers/tty/n_hdlc.c
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Diffstat (limited to 'drivers/tty/n_hdlc.c')
-rw-r--r--drivers/tty/n_hdlc.c60
1 files changed, 41 insertions, 19 deletions
diff --git a/drivers/tty/n_hdlc.c b/drivers/tty/n_hdlc.c
index 12557ee1edb6..1363e659dc1d 100644
--- a/drivers/tty/n_hdlc.c
+++ b/drivers/tty/n_hdlc.c
@@ -416,13 +416,19 @@ static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *data,
* Returns the number of bytes returned or error code.
*/
static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
- __u8 __user *buf, size_t nr)
+ __u8 *kbuf, size_t nr,
+ void **cookie, unsigned long offset)
{
struct n_hdlc *n_hdlc = tty->disc_data;
int ret = 0;
struct n_hdlc_buf *rbuf;
DECLARE_WAITQUEUE(wait, current);
+ /* Is this a repeated call for an rbuf we already found earlier? */
+ rbuf = *cookie;
+ if (rbuf)
+ goto have_rbuf;
+
add_wait_queue(&tty->read_wait, &wait);
for (;;) {
@@ -436,25 +442,8 @@ static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
set_current_state(TASK_INTERRUPTIBLE);
rbuf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
- if (rbuf) {
- if (rbuf->count > nr) {
- /* too large for caller's buffer */
- ret = -EOVERFLOW;
- } else {
- __set_current_state(TASK_RUNNING);
- if (copy_to_user(buf, rbuf->buf, rbuf->count))
- ret = -EFAULT;
- else
- ret = rbuf->count;
- }
-
- if (n_hdlc->rx_free_buf_list.count >
- DEFAULT_RX_BUF_COUNT)
- kfree(rbuf);
- else
- n_hdlc_buf_put(&n_hdlc->rx_free_buf_list, rbuf);
+ if (rbuf)
break;
- }
/* no data */
if (tty_io_nonblock(tty, file)) {
@@ -473,6 +462,39 @@ static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
remove_wait_queue(&tty->read_wait, &wait);
__set_current_state(TASK_RUNNING);
+ if (!rbuf)
+ return ret;
+ *cookie = rbuf;
+
+have_rbuf:
+ /* Have we used it up entirely? */
+ if (offset >= rbuf->count)
+ goto done_with_rbuf;
+
+ /* More data to go, but can't copy any more? EOVERFLOW */
+ ret = -EOVERFLOW;
+ if (!nr)
+ goto done_with_rbuf;
+
+ /* Copy as much data as possible */
+ ret = rbuf->count - offset;
+ if (ret > nr)
+ ret = nr;
+ memcpy(kbuf, rbuf->buf+offset, ret);
+ offset += ret;
+
+ /* If we still have data left, we leave the rbuf in the cookie */
+ if (offset < rbuf->count)
+ return ret;
+
+done_with_rbuf:
+ *cookie = NULL;
+
+ if (n_hdlc->rx_free_buf_list.count > DEFAULT_RX_BUF_COUNT)
+ kfree(rbuf);
+ else
+ n_hdlc_buf_put(&n_hdlc->rx_free_buf_list, rbuf);
+
return ret;
} /* end of n_hdlc_tty_read() */