Revision ea45ea70b6131fa0b006f5b687b9b1398b24f681 authored by Linus Torvalds on 21 July 2013, 17:11:04 UTC, committed by Linus Torvalds on 21 July 2013, 17:11:04 UTC
Pull ACPI video support fixes from Rafael Wysocki: "I'm sending a separate pull request for this as it may be somewhat controversial. The breakage addressed here is not really new and the fixes may not satisfy all users of the affected systems, but we've had so much back and forth dance in this area over the last several weeks that I think it's time to actually make some progress. The source of the problem is that about a year ago we started to tell BIOSes that we're compatible with Windows 8, which we really need to do, because some systems shipping with Windows 8 are tested with it and nothing else, so if we tell their BIOSes that we aren't compatible with Windows 8, we expose our users to untested BIOS/AML code paths. However, as it turns out, some Windows 8-specific AML code paths are not tested either, because Windows 8 actually doesn't use the ACPI methods containing them, so if we declare Windows 8 compatibility and attempt to use those ACPI methods, things break. That occurs mostly in the backlight support area where in particular the _BCM and _BQC methods are plain unusable on some systems if the OS declares Windows 8 compatibility. [ The additional twist is that they actually become usable if the OS says it is not compatible with Windows 8, but that may cause problems to show up elsewhere ] Investigation carried out by Matthew Garrett indicates that what Windows 8 does about backlight is to leave backlight control up to individual graphics drivers. At least there's evidence that it does that if the Intel graphics driver is used, so we've decided to follow Windows 8 in that respect and allow i915 to control backlight (Daniel likes that part). The first commit from Aaron Lu makes ACPICA export the variable from which we can infer whether or not the BIOS believes that we are compatible with Windows 8. The second commit from Matthew Garrett prepares the ACPI video driver by making it initialize the ACPI backlight even if it is not going to be used afterward (that is needed for backlight control to work on Thinkpads). The third commit implements the actual workaround making i915 take over backlight control if the firmware thinks it's dealing with Windows 8 and is based on the work of multiple developers, including Matthew Garrett, Chun-Yi Lee, Seth Forshee, and Aaron Lu. The final commit from Aaron Lu makes us follow Windows 8 by informing the firmware through the _DOS method that it should not carry out automatic brightness changes, so that brightness can be controlled by GUI. Hopefully, this approach will allow us to avoid using blacklists of systems that should not declare Windows 8 compatibility just to avoid backlight control problems in the future. - Change from Aaron Lu makes ACPICA export a variable which can be used by driver code to determine whether or not the BIOS believes that we are compatible with Windows 8. - Change from Matthew Garrett makes the ACPI video driver initialize the ACPI backlight even if it is not going to be used afterward (that is needed for backlight control to work on Thinkpads). - Fix from Rafael J Wysocki implements Windows 8 backlight support workaround making i915 take over bakclight control if the firmware thinks it's dealing with Windows 8. Based on the work of multiple developers including Matthew Garrett, Chun-Yi Lee, Seth Forshee, and Aaron Lu. - Fix from Aaron Lu makes the kernel follow Windows 8 by informing the firmware through the _DOS method that it should not carry out automatic brightness changes, so that brightness can be controlled by GUI" * tag 'acpi-video-3.11' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm: ACPI / video: no automatic brightness changes by win8-compatible firmware ACPI / video / i915: No ACPI backlight if firmware expects Windows 8 ACPI / video: Always call acpi_video_init_brightness() on init ACPICA: expose OSI version
Kbuild
#
# Kbuild for top-level directory of the kernel
# This file takes care of the following:
# 1) Generate bounds.h
# 2) Generate asm-offsets.h (may need bounds.h)
# 3) Check for missing system calls
#####
# 1) Generate bounds.h
bounds-file := include/generated/bounds.h
always := $(bounds-file)
targets := $(bounds-file) kernel/bounds.s
quiet_cmd_bounds = GEN $@
define cmd_bounds
(set -e; \
echo "#ifndef __LINUX_BOUNDS_H__"; \
echo "#define __LINUX_BOUNDS_H__"; \
echo "/*"; \
echo " * DO NOT MODIFY."; \
echo " *"; \
echo " * This file was generated by Kbuild"; \
echo " *"; \
echo " */"; \
echo ""; \
sed -ne $(sed-y) $<; \
echo ""; \
echo "#endif" ) > $@
endef
# We use internal kbuild rules to avoid the "is up to date" message from make
kernel/bounds.s: kernel/bounds.c FORCE
$(Q)mkdir -p $(dir $@)
$(call if_changed_dep,cc_s_c)
$(obj)/$(bounds-file): kernel/bounds.s Kbuild
$(Q)mkdir -p $(dir $@)
$(call cmd,bounds)
#####
# 2) Generate asm-offsets.h
#
offsets-file := include/generated/asm-offsets.h
always += $(offsets-file)
targets += $(offsets-file)
targets += arch/$(SRCARCH)/kernel/asm-offsets.s
# Default sed regexp - multiline due to syntax constraints
define sed-y
"/^->/{s:->#\(.*\):/* \1 */:; \
s:^->\([^ ]*\) [\$$#]*\([-0-9]*\) \(.*\):#define \1 \2 /* \3 */:; \
s:^->\([^ ]*\) [\$$#]*\([^ ]*\) \(.*\):#define \1 \2 /* \3 */:; \
s:->::; p;}"
endef
quiet_cmd_offsets = GEN $@
define cmd_offsets
(set -e; \
echo "#ifndef __ASM_OFFSETS_H__"; \
echo "#define __ASM_OFFSETS_H__"; \
echo "/*"; \
echo " * DO NOT MODIFY."; \
echo " *"; \
echo " * This file was generated by Kbuild"; \
echo " *"; \
echo " */"; \
echo ""; \
sed -ne $(sed-y) $<; \
echo ""; \
echo "#endif" ) > $@
endef
# We use internal kbuild rules to avoid the "is up to date" message from make
arch/$(SRCARCH)/kernel/asm-offsets.s: arch/$(SRCARCH)/kernel/asm-offsets.c \
$(obj)/$(bounds-file) FORCE
$(Q)mkdir -p $(dir $@)
$(call if_changed_dep,cc_s_c)
$(obj)/$(offsets-file): arch/$(SRCARCH)/kernel/asm-offsets.s Kbuild
$(call cmd,offsets)
#####
# 3) Check for missing system calls
#
always += missing-syscalls
targets += missing-syscalls
quiet_cmd_syscalls = CALL $<
cmd_syscalls = $(CONFIG_SHELL) $< $(CC) $(c_flags) $(missing_syscalls_flags)
missing-syscalls: scripts/checksyscalls.sh $(offsets-file) FORCE
$(call cmd,syscalls)
# Keep these two files during make clean
no-clean-files := $(bounds-file) $(offsets-file)
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