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hvc_console: Improve tty/console put_chars handling 

Currently, the hvc_console_print() function drops console output if the
hvc backend's put_chars() returns 0.  This patch changes this behavior
to allow a retry through returning -EAGAIN.

This change also affects the hvc_push() function.  Both functions are
changed to handle -EAGAIN and to retry the put_chars() operation.

If a hvc backend returns -EAGAIN, the retry handling differs:

  - hvc_console_print() spins to write the complete console output.
  - hvc_push() behaves the same way as for returning 0.

Now hvc backends can indirectly control the way how console output is
handled through the hvc console layer.

Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Acked-by: Anton Blanchard <anton@samba.org>
Cc: <stable@kernel.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Hendrik Brueckner 2011-07-05 21:50:18 +00:00 committed by Benjamin Herrenschmidt
parent 63f21a56f1
commit 8c2381af0d
1 changed files with 5 additions and 3 deletions
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8
drivers/tty/hvc/hvc_console.c
View File

@ -163,8 +163,10 @@ static void hvc_console_print(struct console *co, const char *b,
} else {
r = cons_ops[index]->put_chars(vtermnos[index], c, i);
if (r <= 0) {
/* throw away chars on error */
i = 0;
/* throw away characters on error
* but spin in case of -EAGAIN */
if (r != -EAGAIN)
i = 0;
} else if (r > 0) {
i -= r;
if (i > 0)
@ -448,7 +450,7 @@ static int hvc_push(struct hvc_struct *hp)
n = hp->ops->put_chars(hp->vtermno, hp->outbuf, hp->n_outbuf);
if (n <= 0) {
if (n == 0) {
if (n == 0 || n == -EAGAIN) {
hp->do_wakeup = 1;
return 0;
}