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Machine-independent devices

i386-dependent devices

Verbose messages

The ACPIVERBOSE compile time option enables some verbose debug messages printed during the system startup. In a MODULAR (see options(4)) system, the information can be printed also at runtime, regardless of the presence of ACPIVERBOSE. To print the messages, modload(8) the acpiverbose module using the option -b dump=true.

Custom DSDT

ACPI interprets bytecode known as ACPI Machine Language (AML), provided by the BIOS as a memory image during the system bootstrap. Most of the AML relevant to acpi is implemented in the so-called Differentiated System Descriptor Table (DSDT). NetBSD provides support for overriding the default DSDT supplied by the BIOS.

The following steps can be used to override the DSDT:

1. Dump the raw DSDT with acpidump(8).
2. Disassemble the table with iasl(8).
3. Modify the disassembled table.
4. Compile the table with iasl(8) using the option -tc.
5. Either copy the (*.hex) file to

   src/sys/dev/acpi/acpica/Osd/custom_dsdt.hex

   or use the option

   ACPI_DSDT_FILE="/some/directory/custom_dsdt.hex"

   in the kernel configuration file.

6. Define ACPI_DSDT_OVERRIDE in the kernel configuration file and rebuild.

Debugger

The ACPICA interpreter provides its own debugger for low-level debugging. It can be used to display internal data structures and namespace objects, and to debug the execution of control methods. Single step and breakpoint functionality are available. In NetBSD this is integrated to the in-kernel ddb(4). In order to enter the ACPICA debugger from ddb(4), use the command call with the argument acpi_osd_debugger.

Debug Output

NetBSD provides three sysctl(8) variables that control the debug output at runtime. The hw.acpi.debug.layer variable limits the output to a specific ACPI layer and the hw.acpi.debug.level variable controls the debug level. Both sysctl(8) variables are string literals. The third variable is hw.acpi.debug.object. This is a boolean that controls whether debug messages internal to the AML are enabled.

For the first two variables, the possible values are:

In addition, there is ACPI_DEBUG_DEFAULT that is used by ACPICA as the default debug level. It includes ACPI_LV_INIT and ACPI_LV_DEBUG_OBJECT.

The debug layer can be divided into two groups: the first one is specific to the ACPICA interpreter and the second one contains the internal ACPI components of NetBSD. The constant ACPI_ALL_DRIVERS includes all NetBSD specific parts.

The ACPICA interpreter uses several debug levels internally, but the NetBSD specific parts are typically limited to ACPI_LV_DEBUG_OBJECT and ACPI_LV_INFO. The debug output can be stopped by setting hw.acpi.debug.level to ACPI_DEBUG_NONE.

Example

As an example, a driver may have defined the component it belongs to and the name of the module:

#define _COMPONENT	ACPI_BUS_COMPONENT
ACPI_MODULE_NAME	("acpi_example")

The driver may also utilize the debug facility:

ACPI_DEBUG_PRINT((ACPI_DB_INFO, "Failed to evaluate _STA\n"));

With these options the debug message from the ACPI_DEBUG_PRINT macro is only visible when hw.acpi.debug.layer is either ACPI_BUS_COMPONENT or a compound constant including it, and hw.acpi.debug.level is ACPI_LV_INFO or some constant that includes it. Finally, it can be noted that the ACPI implementation uses the prefix ACPI_DB, whereas the debug level sysctl(8) variable is always specified with the prefix ACPI_LV.

Another example can be mentioned for the use of hw.acpi.debug.object. The following could appear in an ASL code:

Method(_Q19, 0, NotSerialized)
{
	Store("_Q19 invoked", Debug)
	Notify(ACAD, 0x80)
}

When hw.acpi.debug.object is set to 1, the message stored to the debug object is printed every time the method is called by the interpreter.