linux-kernel - [PATCH] fbcon: warn on invalid cursor blink intervals

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Date:	Thu, 19 May 2016 17:31:26 -0500 (CDT)
From:	Scot Doyle <lkml14@...tdoyle.com>
To:	Tomi Valkeinen <tomi.valkeinen@...com>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>
cc:	David Daney <david.daney@...ium.com>,
	Ming Lei <ming.lei@...onical.com>,
	Dann Frazier <dann.frazier@...onical.com>,
	Jeremy Kerr <jk@...abs.org>,
	Peter Hurley <peter@...leysoftware.com>,
	Pavel Machek <pavel@....cz>, Jonathan Liu <net147@...il.com>,
	Alistair Popple <alistair@...ple.id.au>,
	Jean-Philippe Brucker <jean-philippe.brucker@....com>,
	"Chintakuntla, Radha" <Radha.Chintakuntla@...iumnetworks.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.com>, David Airlie <airlied@...ux.ie>,
	ddaney.cavm@...il.com, Scot Doyle <lkml14@...tdoyle.com>,
	dri-devel@...ts.freedesktop.org, linux-fbdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: [PATCH] fbcon: warn on invalid cursor blink intervals

Two systems are locking on boot [1] because ops->cur_blink_jiffies
is set to zero from vc->vc_cur_blink_ms.

Ignore such invalid intervals and log a warning.

[1] https://bugs.launchpad.net/bugs/1574814

Suggested-by: David Daney <david.daney@...ium.com>
Signed-off-by: Scot Doyle <lkml14@...tdoyle.com>
Cc: <stable@...r.kernel.org> [v4.2]
---
 drivers/video/console/fbcon.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/drivers/video/console/fbcon.c b/drivers/video/console/fbcon.c
index 6e92917..fad5b89 100644
--- a/drivers/video/console/fbcon.c
+++ b/drivers/video/console/fbcon.c
@@ -1095,7 +1095,13 @@ static void fbcon_init(struct vc_data *vc, int init)
 		con_copy_unimap(vc, svc);
 
 	ops = info->fbcon_par;
-	ops->cur_blink_jiffies = msecs_to_jiffies(vc->vc_cur_blink_ms);
+
+	if (vc->vc_cur_blink_ms >= 50)
+		ops->cur_blink_jiffies =
+		    msecs_to_jiffies(vc->vc_cur_blink_ms);
+	else
+		WARN_ONCE(1, "blink interval < 50 ms");
+
 	p->con_rotate = initial_rotation;
 	set_blitting_type(vc, info);
 
@@ -1309,7 +1315,11 @@ static void fbcon_cursor(struct vc_data *vc, int mode)
 	int y;
  	int c = scr_readw((u16 *) vc->vc_pos);
 
-	ops->cur_blink_jiffies = msecs_to_jiffies(vc->vc_cur_blink_ms);
+	if (vc->vc_cur_blink_ms >= 50)
+		ops->cur_blink_jiffies =
+		    msecs_to_jiffies(vc->vc_cur_blink_ms);
+	else
+		WARN_ONCE(1, "blink interval < 50 ms");
 
 	if (fbcon_is_inactive(vc, info) || vc->vc_deccm != 1)
 		return;
-- 
2.1.4