[PATCH 2/5] vt: Fix up unregistration of vt drivers

Daniel Vetter
2014-06-05T14:59:32Z

A bunch of issues:
- We should not kick out the default console (which is tracked in
conswitchp), so check for that.
- Add better error codes so callers can differentiate between "something
went wrong" and "your driver isn't registered already". i915 needs
that so it doesn't fall over when reloading the driver and hence
vga_con is already unregistered.
- There's a mess with the driver flags: What we need to check for is
that the driver isn't used any more, i.e. unbound completely (FLAG_INIT).
And not whether it's the boot console or not (which is the only one
which doesn't have FLAG_MODULE). Otherwise there's no way to kick
out the boot console, which i915 wants to do to prevent havoc with
vga_con interferring (which tends to hang machines).

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
---
drivers/tty/vt/vt.c | 16 +++++++++-------
1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
index ea600f482eeb..5077fe87324d 100644
--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c
@@ -3573,17 +3573,20 @@ err:
*/
int do_unregister_con_driver(const struct consw *csw)
{
- int i, retval = -ENODEV;
+ int i;

/* cannot unregister a bound driver */
if (con_is_bound(csw))
- goto err;
+ return -EBUSY;
+
+ if (csw == conswitchp)
+ return -EINVAL;

for (i = 0; i < MAX_NR_CON_DRIVER; i++) {
struct con_driver *con_driver = &registered_con_driver[i];

if (con_driver->con == csw &&
- con_driver->flag & CON_DRIVER_FLAG_MODULE) {
+ con_driver->flag & CON_DRIVER_FLAG_INIT) {
vtconsole_deinit_device(con_driver);
device_destroy(vtconsole_class,
MKDEV(0, con_driver->node));
@@ -3594,12 +3597,11 @@ int do_unregister_con_driver(const struct consw *csw)
con_driver->flag = 0;
con_driver->first = 0;
con_driver->last = 0;
- retval = 0;
- break;
+ return 0;
}
}
-err:
- return retval;
+
+ return -ENODEV;
}
EXPORT_SYMBOL_GPL(do_unregister_con_driver);

--
1.8.1.4