| From 230ee59de286a459a37417eb797af77bd8cb0642 Mon Sep 17 00:00:00 2001 |
| From: Hendrik Brueckner <brueckner@linux.vnet.ibm.com> |
| Date: Tue, 5 Jul 2011 21:50:18 +0000 |
| Subject: [PATCH] hvc_console: Improve tty/console put_chars handling |
| |
| commit 8c2381af0d3ef62a681dac5a141b6dabb27bf2e1 upstream. |
| |
| 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> |
| Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> |
| [PG: map drivers/tty/hvc/ --> drivers/char for v2.6.34 baseline] |
| |
| Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> |
| |
| diff --git a/drivers/char/hvc_console.c b/drivers/char/hvc_console.c |
| index 35cca4c..8417efe 100644 |
| --- a/drivers/char/hvc_console.c |
| +++ b/drivers/char/hvc_console.c |
| @@ -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; |
| } |
| -- |
| 1.7.12.rc1.1.gbce1580 |
| |
