ACPI: support customizing ACPI control methods at runtime

Introduce a new debugfs I/F (/sys/kernel/debug/acpi/custom_method) for ACPI,
which can be used to customize the ACPI control methods at runtime.

We can use this to debug the AML code level bugs instead of overriding the
whole DSDT table, without rebuilding/rebooting kernel any more.

Detailed description about how to use this debugfs I/F is stated in
Documentation/acpi/method-customizing.txt

Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>

1 files changed, 82 insertions, 1 deletions

diff --git a/drivers/acpi/debug.c b/drivers/acpi/debug.c
index 8a690c3b8e23..0bedd1554f2f 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 +197,79 @@ 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;
+        }
+
+        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 +360,7 @@ 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 +395,10 @@ int __init acpi_debug_init(void)
         return 0;
 #endif
 }
+
+int __init acpi_debug_init(void)
+{
+        acpi_debugfs_init();
+        acpi_procfs_init();
+        return 0;
+}