summaryrefslogtreecommitdiff
path: root/drivers/tty/vt
diff options
context:
space:
mode:
authorYifeng Li <tomli@tomli.me>2019-03-05 07:02:49 +0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2019-03-28 01:28:23 +0900
commit75ddbc1fb11efac87b611d48e9802f6fe2bb2163 (patch)
tree4910a343069646c6396f8b620c432b87bfa4eddf /drivers/tty/vt
parent46ca3f735f345c9d87383dd3a09fa5d43870770e (diff)
tty: vt.c: Fix TIOCL_BLANKSCREEN console blanking if blankinterval == 0
Previously, in the userspace, it was possible to use the "setterm" command from util-linux to blank the VT console by default, using the following command. According to the man page, > The force option keeps the screen blank even if a key is pressed. It was implemented by calling TIOCL_BLANKSCREEN. case BLANKSCREEN: ioctlarg = TIOCL_BLANKSCREEN; if (ioctl(STDIN_FILENO, TIOCLINUX, &ioctlarg)) warn(_("cannot force blank")); break; However, after Linux 4.12, this command ceased to work anymore, which is unexpected. By inspecting the kernel source, it shows that the issue was triggered by the side-effect from commit a4199f5eb809 ("tty: Disable default console blanking interval"). The console blanking is implemented by function do_blank_screen() in vt.c: "blank_state" will be initialized to "blank_normal_wait" in con_init() if AND ONLY IF ("blankinterval" > 0). If "blankinterval" is 0, "blank_state" will be "blank_off" (== 0), and a call to do_blank_screen() will always abort, even if a forced blanking is required from the user by calling TIOCL_BLANKSCREEN, the console won't be blanked. This behavior is unexpected from a user's point-of-view, since it's not mentioned in any documentation. The setterm man page suggests it will always work, and the kernel comments in uapi/linux/tiocl.h says > /* keep screen blank even if a key is pressed */ > #define TIOCL_BLANKSCREEN 14 To fix it, we simply remove the "blank_state != blank_off" check, as pointed out by Nicolas Pitre, this check doesn't logically make sense and it's safe to remove. Suggested-by: Nicolas Pitre <nicolas.pitre@linaro.org> Fixes: a4199f5eb809 ("tty: Disable default console blanking interval") Signed-off-by: Yifeng Li <tomli@tomli.me> Cc: stable <stable@vger.kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty/vt')
-rw-r--r--drivers/tty/vt/vt.c2
1 files changed, 0 insertions, 2 deletions
diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
index d34984aa646d..721edee50234 100644
--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c
@@ -4178,8 +4178,6 @@ void do_blank_screen(int entering_gfx)
return;
}
- if (blank_state != blank_normal_wait)
- return;
blank_state = blank_off;
/* don't blank graphics */