Revision bd8733738c5af6114dd15d340b3f8713e9b624c2 authored by Boris Brezillon on 08 February 2015, 18:23:42 UTC, committed by Linus Walleij on 18 March 2015, 01:01:36 UTC
The gpiochip_lock_as_irq call can fail and return an error, while the irq_startup is not expected to fail (returns an unsigned int which is not checked by irq core code). irq_request/release_resources functions have been created to address this problem. Move gpiochip_lock/unlock_as_irq calls into irq_request/release_resources functions to prevent using a gpio as an irq if the gpiochip_lock_as_irq call failed. Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com> Acked-by: Ludovic Desroches <ludovic.desroches@atmel.com> Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com> Acked-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
1 parent 549e783
initrd_table_override.txt
Overriding ACPI tables via initrd
=================================
1) Introduction (What is this about)
2) What is this for
3) How does it work
4) References (Where to retrieve userspace tools)
1) What is this about
---------------------
If the ACPI_INITRD_TABLE_OVERRIDE compile option is true, it is possible to
override nearly any ACPI table provided by the BIOS with an instrumented,
modified one.
For a full list of ACPI tables that can be overridden, take a look at
the char *table_sigs[MAX_ACPI_SIGNATURE]; definition in drivers/acpi/osl.c
All ACPI tables iasl (Intel's ACPI compiler and disassembler) knows should
be overridable, except:
- ACPI_SIG_RSDP (has a signature of 6 bytes)
- ACPI_SIG_FACS (does not have an ordinary ACPI table header)
Both could get implemented as well.
2) What is this for
-------------------
Please keep in mind that this is a debug option.
ACPI tables should not get overridden for productive use.
If BIOS ACPI tables are overridden the kernel will get tainted with the
TAINT_OVERRIDDEN_ACPI_TABLE flag.
Complain to your platform/BIOS vendor if you find a bug which is so sever
that a workaround is not accepted in the Linux kernel.
Still, it can and should be enabled in any kernel, because:
- There is no functional change with not instrumented initrds
- It provides a powerful feature to easily debug and test ACPI BIOS table
compatibility with the Linux kernel.
3) How does it work
-------------------
# Extract the machine's ACPI tables:
cd /tmp
acpidump >acpidump
acpixtract -a acpidump
# Disassemble, modify and recompile them:
iasl -d *.dat
# For example add this statement into a _PRT (PCI Routing Table) function
# of the DSDT:
Store("HELLO WORLD", debug)
iasl -sa dsdt.dsl
# Add the raw ACPI tables to an uncompressed cpio archive.
# They must be put into a /kernel/firmware/acpi directory inside the
# cpio archive.
# The uncompressed cpio archive must be the first.
# Other, typically compressed cpio archives, must be
# concatenated on top of the uncompressed one.
mkdir -p kernel/firmware/acpi
cp dsdt.aml kernel/firmware/acpi
# A maximum of: #define ACPI_OVERRIDE_TABLES 10
# tables are currently allowed (see osl.c):
iasl -sa facp.dsl
iasl -sa ssdt1.dsl
cp facp.aml kernel/firmware/acpi
cp ssdt1.aml kernel/firmware/acpi
# Create the uncompressed cpio archive and concatenate the original initrd
# on top:
find kernel | cpio -H newc --create > /boot/instrumented_initrd
cat /boot/initrd >>/boot/instrumented_initrd
# reboot with increased acpi debug level, e.g. boot params:
acpi.debug_level=0x2 acpi.debug_layer=0xFFFFFFFF
# and check your syslog:
[ 1.268089] ACPI: PCI Interrupt Routing Table [\_SB_.PCI0._PRT]
[ 1.272091] [ACPI Debug] String [0x0B] "HELLO WORLD"
iasl is able to disassemble and recompile quite a lot different,
also static ACPI tables.
4) Where to retrieve userspace tools
------------------------------------
iasl and acpixtract are part of Intel's ACPICA project:
http://acpica.org/
and should be packaged by distributions (for example in the acpica package
on SUSE).
acpidump can be found in Len Browns pmtools:
ftp://kernel.org/pub/linux/kernel/people/lenb/acpi/utils/pmtools/acpidump
This tool is also part of the acpica package on SUSE.
Alternatively, used ACPI tables can be retrieved via sysfs in latest kernels:
/sys/firmware/acpi/tables
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