diff options
| -rw-r--r-- | Documentation/acpi/method-customizing.txt | 66 | ||||
| -rw-r--r-- | drivers/acpi/debug.c | 84 |
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; +} |