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-rw-r--r--Documentation/acpi/method-customizing.txt66
-rw-r--r--drivers/acpi/debug.c84
2 files changed, 149 insertions, 1 deletions
diff --git a/Documentation/acpi/method-customizing.txt b/Documentation/acpi/method-customizing.txt
new file mode 100644
index 00000000000..e628cd23ca8
--- /dev/null
+++ b/Documentation/acpi/method-customizing.txt
@@ -0,0 +1,66 @@
+Linux ACPI Custom Control Method How To
+=======================================
+
+Written by Zhang Rui <rui.zhang@intel.com>
+
+
+Linux supports customizing ACPI control methods at runtime.
+
+Users can use this to
+1. override an existing method which may not work correctly,
+ or just for debugging purposes.
+2. insert a completely new method in order to create a missing
+ method such as _OFF, _ON, _STA, _INI, etc.
+For these cases, it is far simpler to dynamically install a single
+control method rather than override the entire DSDT, because kernel
+rebuild/reboot is not needed and test result can be got in minutes.
+
+Note: Only ACPI METHOD can be overridden, any other object types like
+ "Device", "OperationRegion", are not recognized.
+Note: The same ACPI control method can be overridden for many times,
+ and it's always the latest one that used by Linux/kernel.
+
+1. override an existing method
+ a) get the ACPI table via ACPI sysfs I/F. e.g. to get the DSDT,
+ just run "cat /sys/firmware/acpi/tables/DSDT > /tmp/dsdt.dat"
+ b) disassemble the table by running "iasl -d dsdt.dat".
+ c) rewrite the ASL code of the method and save it in a new file,
+ d) package the new file (psr.asl) to an ACPI table format.
+ Here is an example of a customized \_SB._AC._PSR method,
+
+ DefinitionBlock ("", "SSDT", 1, "", "", 0x20080715)
+ {
+ External (ACON)
+
+ Method (\_SB_.AC._PSR, 0, NotSerialized)
+ {
+ Store ("In AC _PSR", Debug)
+ Return (ACON)
+ }
+ }
+ Note that the full pathname of the method in ACPI namespace
+ should be used.
+ And remember to use "External" to declare external objects.
+ e) assemble the file to generate the AML code of the method.
+ e.g. "iasl psr.asl" (psr.aml is generated as a result)
+ f) mount debugfs by "mount -t debugfs none /sys/kernel/debug"
+ g) override the old method via the debugfs by running
+ "cat /tmp/psr.aml > /sys/kernel/debug/acpi/custom_method"
+
+2. insert a new method
+ This is easier than overriding an existing method.
+ We just need to create the ASL code of the method we want to
+ insert and then follow the step c) ~ g) in section 1.
+
+3. undo your changes
+ The "undo" operation is not supported for a new inserted method
+ right now, i.e. we can not remove a method currently.
+ For an overrided method, in order to undo your changes, please
+ save a copy of the method original ASL code in step c) section 1,
+ and redo step c) ~ g) to override the method with the original one.
+
+
+Note: We can use a kernel with multiple custom ACPI method running,
+ But each individual write to debugfs can implement a SINGLE
+ method override. i.e. if we want to insert/override multiple
+ ACPI methods, we need to redo step c) ~ g) for multiple times.
diff --git a/drivers/acpi/debug.c b/drivers/acpi/debug.c
index 8a690c3b8e2..cc421b7ae16 100644
--- a/drivers/acpi/debug.c
+++ b/drivers/acpi/debug.c
@@ -8,6 +8,7 @@
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/moduleparam.h>
+#include <linux/debugfs.h>
#include <asm/uaccess.h>
#include <acpi/acpi_drivers.h>
@@ -196,6 +197,80 @@ module_param_call(trace_state, param_set_trace_state, param_get_trace_state,
NULL, 0644);
/* --------------------------------------------------------------------------
+ DebugFS Interface
+ -------------------------------------------------------------------------- */
+
+static ssize_t cm_write(struct file *file, const char __user *user_buf,
+ size_t count, loff_t *ppos)
+{
+ static char *buf;
+ static int uncopied_bytes;
+ struct acpi_table_header table;
+ acpi_status status;
+
+ if (!(*ppos)) {
+ /* parse the table header to get the table length */
+ if (count <= sizeof(struct acpi_table_header))
+ return -EINVAL;
+ if (copy_from_user(&table, user_buf,
+ sizeof(struct acpi_table_header)))
+ return -EFAULT;
+ uncopied_bytes = table.length;
+ buf = kzalloc(uncopied_bytes, GFP_KERNEL);
+ if (!buf)
+ return -ENOMEM;
+ }
+
+ if (uncopied_bytes < count) {
+ kfree(buf);
+ return -EINVAL;
+ }
+
+ if (copy_from_user(buf + (*ppos), user_buf, count)) {
+ kfree(buf);
+ return -EFAULT;
+ }
+
+ uncopied_bytes -= count;
+ *ppos += count;
+
+ if (!uncopied_bytes) {
+ status = acpi_install_method(buf);
+ kfree(buf);
+ if (ACPI_FAILURE(status))
+ return -EINVAL;
+ add_taint(TAINT_OVERRIDDEN_ACPI_TABLE);
+ }
+
+ return count;
+}
+
+static const struct file_operations cm_fops = {
+ .write = cm_write,
+};
+
+static int acpi_debugfs_init(void)
+{
+ struct dentry *acpi_dir, *cm_dentry;
+
+ acpi_dir = debugfs_create_dir("acpi", NULL);
+ if (!acpi_dir)
+ goto err;
+
+ cm_dentry = debugfs_create_file("custom_method", S_IWUGO,
+ acpi_dir, NULL, &cm_fops);
+ if (!cm_dentry)
+ goto err;
+
+ return 0;
+
+err:
+ if (acpi_dir)
+ debugfs_remove(acpi_dir);
+ return -EINVAL;
+}
+
+/* --------------------------------------------------------------------------
FS Interface (/proc)
-------------------------------------------------------------------------- */
#ifdef CONFIG_ACPI_PROCFS
@@ -286,7 +361,7 @@ static const struct file_operations acpi_system_debug_proc_fops = {
};
#endif
-int __init acpi_debug_init(void)
+int __init acpi_procfs_init(void)
{
#ifdef CONFIG_ACPI_PROCFS
struct proc_dir_entry *entry;
@@ -321,3 +396,10 @@ int __init acpi_debug_init(void)
return 0;
#endif
}
+
+int __init acpi_debug_init(void)
+{
+ acpi_debugfs_init();
+ acpi_procfs_init();
+ return 0;
+}