Revision 0a4c56c80f90797e9b9f8426c6aae4c0cf1c9785 authored by Linus Torvalds on 29 August 2020, 20:50:56 UTC, committed by Linus Torvalds on 29 August 2020, 20:50:56 UTC
Commit ef91bb196b0d ("kernel.h: Silence sparse warning in lower_32_bits") caused new warnings to show in the fsldma driver, but that commit was not to blame: it only exposed some very incorrect code that tried to take the low 32 bits of an address. That made no sense for multiple reasons, the most notable one being that that code was intentionally limited to only 32-bit ppc builds, so "only low 32 bits of an address" was completely nonsensical. There were no high bits to mask off to begin with. But even more importantly fropm a correctness standpoint, turning the address into an integer then caused the subsequent address arithmetic to be completely wrong too, and the "+1" actually incremented the address by one, rather than by four. Which again was incorrect, since the code was reading two 32-bit values and trying to make a 64-bit end result of it all. Surprisingly, the iowrite64() did not suffer from the same odd and incorrect model. This code has never worked, but it's questionable whether anybody cared: of the two users that actually read the 64-bit value (by way of some C preprocessor hackery and eventually the 'get_cdar()' inline function), one of them explicitly ignored the value, and the other one might just happen to work despite the incorrect value being read. This patch at least makes it not fail the build any more, and makes the logic superficially sane. Whether it makes any difference to the code _working_ or not shall remain a mystery. Compile-tested-by: Guenter Roeck <linux@roeck-us.net> Reviewed-by: Guenter Roeck <linux@roeck-us.net> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Kconfig
# SPDX-License-Identifier: GPL-2.0-only
config SYSFS
bool "sysfs file system support" if EXPERT
default y
select KERNFS
help
The sysfs filesystem is a virtual filesystem that the kernel uses to
export internal kernel objects, their attributes, and their
relationships to one another.
Users can use sysfs to ascertain useful information about the running
kernel, such as the devices the kernel has discovered on each bus and
which driver each is bound to. sysfs can also be used to tune devices
and other kernel subsystems.
Some system agents rely on the information in sysfs to operate.
/sbin/hotplug uses device and object attributes in sysfs to assist in
delegating policy decisions, like persistently naming devices.
sysfs is currently used by the block subsystem to mount the root
partition. If sysfs is disabled you must specify the boot device on
the kernel boot command line via its major and minor numbers. For
example, "root=03:01" for /dev/hda1.
Designers of embedded systems may wish to say N here to conserve space.
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