Add a new tain flag that indicates wheather the user has loaded ACPI
SSDT overlays. This will provide a clean indication in bug reports that
the user has added new information to the ACPI tables.
Signed-off-by: Octavian Purdila <octavian.purdila@xxxxxxxxx>
---
Documentation/acpi/ssdt-overlays.txt | 64 ++++++++++++++++++++++++++++++++++++
Documentation/oops-tracing.txt | 2 ++
Documentation/sysctl/kernel.txt | 1 +
include/linux/kernel.h | 1 +
kernel/panic.c | 2 ++
5 files changed, 70 insertions(+)
create mode 100644 Documentation/acpi/ssdt-overlays.txt
diff --git a/Documentation/acpi/ssdt-overlays.txt b/Documentation/acpi/ssdt-overlays.txt
new file mode 100644
index 0000000..54ee74a
--- /dev/null
+++ b/Documentation/acpi/ssdt-overlays.txt
@@ -0,0 +1,64 @@
+
+In order to support ACPI open-ended hardware configurations (e.g. development
+boards) we need a way to augment the ACPI configuration provided by the firmware
+image. A common example is connecting sensors on I2C / SPI buses on development
+boards.
+
+Although this can be accomplished by creating a kernel platform driver or
+recompiling the firmware image with updated ACPI tables, neither is practical:
+the former proliferates board specific kernel code while the latter requires
+access to firmware tools which are often not publicly available.
+
+Because ACPI supports external references in AML code a more practical
+way to augment firmware ACPI configuration is by dynamically loading
+user defined SSDT tables that contain the board specific information.
+
+For example, to enumerate a Bosch BMA222E accelerometer on the I2C bus of the
+Minnowboard MAX development board exposed via the LSE connector [1], the
+following ASL code can be used:
+
+DefinitionBlock ("minnowmax.aml", "SSDT", 1, "Vendor", "Accel", 0x00000003)
+{
+ External (\_SB.I2C6, DeviceObj)
+
+ Scope (\_SB.I2C6)
+ {
+ Device (STAC)
+ {
+ Name (_ADR, Zero)
+ Name (_HID, "BMA222E")
+
+ Method (_CRS, 0, Serialized)
+ {
+ Name (RBUF, ResourceTemplate ()
+ {
+ I2cSerialBus (0x0018, ControllerInitiated, 0x00061A80,
+ AddressingMode7Bit, "\\_SB.I2C6", 0x00,
+ ResourceConsumer, ,)
+ GpioInt (Edge, ActiveHigh, Exclusive, PullDown, 0x0000,
+ "\\_SB.GPO2", 0x00, ResourceConsumer, , )
+ { // Pin list
+ 0
+ }
+ })
+ Return (RBUF)
+ }
+ }
+ }
+}
+
+which can then be compiled to AML binary format:
+
+$ iasl minnowmax.asl
+
+Intel ACPI Component Architecture
+ASL Optimizing Compiler version 20140214-64 [Mar 29 2014]
+Copyright (c) 2000 - 2014 Intel Corporation
+
+ASL Input: minnomax.asl - 30 lines, 614 bytes, 7 keywords
+AML Output: minnowmax.aml - 165 bytes, 6 named objects, 1 executable opcodes
+
+[1] http://wiki.minnowboard.org/MinnowBoard_MAX#Low_Speed_Expansion_Connector_.28Top.29
+
+The resulting AML code can then be loaded by the kernel using one of the methods
+below.
diff --git a/Documentation/oops-tracing.txt b/Documentation/oops-tracing.txt
index f3ac05c..40e1117 100644
--- a/Documentation/oops-tracing.txt
+++ b/Documentation/oops-tracing.txt
@@ -272,6 +272,8 @@ characters, each representing a particular tainted value.
16: 'K' if the kernel has been live patched.
+ 17: 'N' if ACPI SSDT overlays have been loaded.
+
The primary reason for the 'Tainted: ' string is to tell kernel
debuggers if this is a clean kernel or if anything unusual has
occurred. Tainting is permanent: even if an offending module is
diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
index 57653a4..e68d4168 100644
--- a/Documentation/sysctl/kernel.txt
+++ b/Documentation/sysctl/kernel.txt
@@ -917,6 +917,7 @@ can be ORed together:
signature.
16384 - A soft lockup has previously occurred on the system.
32768 - The kernel has been live patched.
+65536 - ACPI SSDT overlays have been loaded.
==============================================================
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 2f7775e..8c90125 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -502,6 +502,7 @@ extern enum system_states {
#define TAINT_UNSIGNED_MODULE 13
#define TAINT_SOFTLOCKUP 14
#define TAINT_LIVEPATCH 15
+#define TAINT_OVERLAY_ACPI_TABLE 16
extern const char hex_asc[];
#define hex_asc_lo(x) hex_asc[((x) & 0x0f)]
diff --git a/kernel/panic.c b/kernel/panic.c
index 535c965..1ff0819 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -284,6 +284,7 @@ static const struct tnt tnts[] = {
{ TAINT_UNSIGNED_MODULE, 'E', ' ' },
{ TAINT_SOFTLOCKUP, 'L', ' ' },
{ TAINT_LIVEPATCH, 'K', ' ' },
+ { TAINT_OVERLAY_ACPI_TABLE, 'N', ' ' },
};
/**
@@ -305,6 +306,7 @@ static const struct tnt tnts[] = {
* 'E' - Unsigned module has been loaded.
* 'L' - A soft lockup has previously occurred.
* 'K' - Kernel has been live patched.
+ * 'N' - ACPI SSDT overlays have been loaded.
*
* The string is overwritten by the next call to print_tainted().
*/
--
1.9.1
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