Commit 2c4e9671 authored Aug 28, 2010 by Arnd Bergmann Committed by Dmitry Torokhov Aug 28, 2010

Input: use PIT_TICK_RATE in vt beep ioctl



The KIOCSOUND and KDMKTONE ioctls are based on the CLOCK_TICK_RATE,
which is architecture and sometimes configuration specific.

In practice, most user applications assume that it is actually defined
as the i8253 PIT base clock of 1193182 Hz, which is true on some
architectures but not on others.

This patch makes the vt code use the PIT frequency on all
architectures, which is much more well-defined.  It will change the
behavior of user applications sending the beep ioctl on all
architectures that define CLOCK_TICK_RATE different from
PIT_TICK_RATE.

The original breakage was introduced in commit bcc8ca09 "Adapt
drivers/char/vt_ioctl.c to non-x86".  Hopefully, reverting this change
will make the frequency correct in more cases than it will make it
incorrect.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

parent d9f66c1a

drivers/char/vt_ioctl.c

+8 −8

Original line number	Diff line number	Diff line
		@@ -533,11 +533,14 @@ int vt_ioctl(struct tty_struct tty, struct file file,
		case KIOCSOUND:
		if (!perm)
		goto eperm;
		/* FIXME: This is an old broken API but we need to keep it
		supported and somehow separate the historic advertised
		tick rate from any real one */
		/*
		* The use of PIT_TICK_RATE is historic, it used to be
		* the platform-dependent CLOCK_TICK_RATE between 2.6.12
		* and 2.6.36, which was a minor but unfortunate ABI
		* change.
		*/
		if (arg)
		arg = CLOCK_TICK_RATE / arg;
		arg = PIT_TICK_RATE / arg;
		kd_mksound(arg, 0);
		break;

		@@ -553,11 +556,8 @@ int vt_ioctl(struct tty_struct tty, struct file file,
		*/
		ticks = HZ * ((arg >> 16) & 0xffff) / 1000;
		count = ticks ? (arg & 0xffff) : 0;
		/* FIXME: This is an old broken API but we need to keep it
		supported and somehow separate the historic advertised
		tick rate from any real one */
		if (count)
		count = CLOCK_TICK_RATE / count;
		count = PIT_TICK_RATE / count;
		kd_mksound(count, ticks);
		break;
		}