linux-kernel - [PATCH] vt: Don't check KD_GRAPHICS when binding/unbinding

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Date:	Mon, 13 Apr 2015 11:16:21 +0200
From:	Daniel Vetter <daniel.vetter@...ll.ch>
To:	DRI Development <dri-devel@...ts.freedesktop.org>,
	LKML <linux-kernel@...r.kernel.org>
Cc:	Intel Graphics Development <intel-gfx@...ts.freedesktop.org>,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Antonino A. Daplas" <adaplas@...il.com>,
	David Herrmann <dh.herrmann@...il.com>,
	Peter Hurley <peter@...leysoftware.com>,
	Imre Deak <imre.deak@...el.com>,
	Daniel Vetter <daniel.vetter@...el.com>
Subject: [PATCH] vt: Don't check KD_GRAPHICS when binding/unbinding

This was introduced in

commit 6db4063c5b72b46e9793b0f141a7a3984ac6facf
Author: Antonino A. Daplas <adaplas@...il.com>
Date:   Mon Jun 26 00:27:12 2006 -0700

    [PATCH] VT binding: Add sysfs control to the VT layer

with the justification

    "In addition, if any of the consoles are in KD_GRAPHICS mode, binding and
    unbinding will not succeed.  KD_GRAPHICS mode usually indicates that the
    underlying console hardware is used for other purposes other than displaying
    text (ie X).  This feature should prevent binding/unbinding from interfering
    with a graphics application using the VT."

I think we should lift this artificial restriction though:
- KD_GRAPHICS doesn't get cleaned up automatically, which means it's
  easy to have terminals stuck in KD_GRAPHICS when hacking around on
  X.
- X doesn't really care, especially with drm where kms already blocks
  fbdev (and hence fbcon) when there's an active compositor.
- This is a root-only interface with a separate .config option and
  it's possible to hang your machine already anyway if you
  unload/reload drivers and don't know what you're doing.

With this patch i915.ko module reloading works again reliably,
something in the recent fedora upgrades broke things.

Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Antonino A. Daplas <adaplas@...il.com>
Cc: David Herrmann <dh.herrmann@...il.com>
Cc: Peter Hurley <peter@...leysoftware.com>
Cc: Imre Deak <imre.deak@...el.com>
Signed-off-by: Daniel Vetter <daniel.vetter@...el.com>
---
 drivers/tty/vt/vt.c | 22 ++--------------------
 1 file changed, 2 insertions(+), 20 deletions(-)

diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
index 6e00572cbeb9..b84f7d80c8b4 100644
--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c
@@ -3185,22 +3185,6 @@ err:
 
 
 #ifdef CONFIG_VT_HW_CONSOLE_BINDING
-static int con_is_graphics(const struct consw *csw, int first, int last)
-{
-	int i, retval = 0;
-
-	for (i = first; i <= last; i++) {
-		struct vc_data *vc = vc_cons[i].d;
-
-		if (vc && vc->vc_mode == KD_GRAPHICS) {
-			retval = 1;
-			break;
-		}
-	}
-
-	return retval;
-}
-
 /* unlocked version of unbind_con_driver() */
 int do_unbind_con_driver(const struct consw *csw, int first, int last, int deflt)
 {
@@ -3286,8 +3270,7 @@ static int vt_bind(struct con_driver *con)
 	const struct consw *defcsw = NULL, *csw = NULL;
 	int i, more = 1, first = -1, last = -1, deflt = 0;
 
- 	if (!con->con || !(con->flag & CON_DRIVER_FLAG_MODULE) ||
-	    con_is_graphics(con->con, con->first, con->last))
+ 	if (!con->con || !(con->flag & CON_DRIVER_FLAG_MODULE))
 		goto err;
 
 	csw = con->con;
@@ -3338,8 +3321,7 @@ static int vt_unbind(struct con_driver *con)
 	int i, more = 1, first = -1, last = -1, deflt = 0;
 	int ret;
 
- 	if (!con->con || !(con->flag & CON_DRIVER_FLAG_MODULE) ||
-	    con_is_graphics(con->con, con->first, con->last))
+ 	if (!con->con || !(con->flag & CON_DRIVER_FLAG_MODULE))
 		goto err;
 
 	csw = con->con;
-- 
2.1.0

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