linux-uconsole/include
Linus Torvalds c1f95ce58f linux/log2.h: Fix rounddown_pow_of_two(1)
commit 13c07b0286 upstream.

Exactly like roundup_pow_of_two(1), the rounddown version was buggy for
the case of a compile-time constant '1' argument.  Probably because it
originated from the same code, sharing history with the roundup version
from before the bugfix (for that one, see commit 1a06a52ee1: "Fix
roundup_pow_of_two(1)").

However, unlike the roundup version, the fix for rounddown is to just
remove the broken special case entirely.  It's simply not needed - the
generic code

    1UL << ilog2(n)

does the right thing for the constant '1' argment too.  The only reason
roundup needed that special case was because rounding up does so by
subtracting one from the argument (and then adding one to the result)
causing the obvious problems with "ilog2(0)".

But rounddown doesn't do any of that, since ilog2() naturally truncates
(ie "rounds down") to the right rounded down value.  And without the
ilog2(0) case, there's no reason for the special case that had the wrong
value.

tl;dr: rounddown_pow_of_two(1) should be 1, not 0.

Acked-by: Dmitry Torokhov <dtor@vmware.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2011-12-21 12:57:38 -08:00
..
acpi Merge branches 'd3cold', 'bugzilla-37412' and 'bugzilla-38152' into release 2011-07-14 00:16:38 -04:00
asm-generic Merge branches 'gpio/merge' and 'spi/merge' of git://git.secretlab.ca/git/linux-2.6 2011-06-17 10:36:32 -07:00
crypto
drm drm/radeon/kms: add some new pci ids 2011-12-09 08:52:37 -08:00
keys
linux linux/log2.h: Fix rounddown_pow_of_two(1) 2011-12-21 12:57:38 -08:00
math-emu
media [media] tuner-core/v4l2-subdev: document that the type field has to be filled in 2011-07-07 15:04:23 -03:00
mtd
net net: Handle different key sizes between address families in flow cache 2011-11-11 09:37:17 -08:00
pcmcia
rdma Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/roland/infiniband 2011-05-26 12:13:57 -07:00
rxrpc
scsi [SCSI] libsas: Add option for SATA soft reset 2011-05-26 22:49:33 -05:00
sound ALSA: sb16 - Fix build errors on MIPS and others with 13bit ioctl size 2011-06-30 15:33:57 +02:00
target [SCSI] target: Convert REPORT_LUNs to use int_to_scsilun 2011-05-24 13:02:42 -04:00
trace Merge branch 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4 2011-06-21 10:22:35 -07:00
video Merge branches 'common/fbdev' and 'common/fbdev-meram' of master.kernel.org:/pub/scm/linux/kernel/git/lethal/sh-2.6 2011-05-24 15:49:57 +09:00
xen xen: allow enable use of VGA console on dom0 2011-08-15 18:31:34 -07:00
Kbuild