ACPI: basic initramfs DSDT override support

[linux-2.6] / drivers / acpi / osl.c

diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
index e53fb516f9d45538dbfdedc002ad3dcb753e200e..131936e7ff1765d6663c5813a0781555673aa2a7 100644 (file)
--- a/drivers/acpi/osl.c
+++ b/drivers/acpi/osl.c
@@ -312,6 +312,66 @@ acpi_os_predefined_override(const struct acpi_predefined_names *init_val,
        return AE_OK;
 }
 
+#ifdef CONFIG_ACPI_CUSTOM_DSDT_INITRD
+struct acpi_table_header *acpi_find_dsdt_initrd(void)
+{
+       struct file *firmware_file;
+       mm_segment_t oldfs;
+       unsigned long len, len2;
+       struct acpi_table_header *dsdt_buffer, *ret = NULL;
+       struct kstat stat;
+       char *ramfs_dsdt_name = "/DSDT.aml";
+
+       printk(KERN_INFO PREFIX "Looking for DSDT in initramfs... ");
+
+       /*
+        * Never do this at home, only the user-space is allowed to open a file.
+        * The clean way would be to use the firmware loader. But this code must be run
+        * before there is any userspace available. So we need a static/init firmware
+        * infrastructure, which doesn't exist yet...
+        */
+       if (vfs_stat(ramfs_dsdt_name, &stat) < 0) {
+               printk("not found.\n");
+               return ret;
+       }
+
+       len = stat.size;
+       /* check especially against empty files */
+       if (len <= 4) {
+               printk("error, file is too small: only %lu bytes.\n", len);
+               return ret;
+       }
+
+       firmware_file = filp_open(ramfs_dsdt_name, O_RDONLY, 0);
+       if (IS_ERR(firmware_file)) {
+               printk("error, could not open file %s.\n", ramfs_dsdt_name);
+               return ret;
+       }
+
+       dsdt_buffer = ACPI_ALLOCATE(len);
+       if (!dsdt_buffer) {
+               printk("error when allocating %lu bytes of memory.\n", len);
+               goto err;
+       }
+
+       oldfs = get_fs();
+       set_fs(KERNEL_DS);
+       len2 = vfs_read(firmware_file, (char __user *)dsdt_buffer, len, &firmware_file->f_pos);
+       set_fs(oldfs);
+       if (len2 < len) {
+               printk("error trying to read %lu bytes from %s.\n", len, ramfs_dsdt_name);
+               ACPI_FREE(dsdt_buffer);
+               goto err;
+       }
+
+       printk("successfully read %lu bytes from %s.\n", len, ramfs_dsdt_name);
+       ret = dsdt_buffer;
+err:
+       filp_close(firmware_file, NULL);
+       return ret;
+}
+#endif
+
 acpi_status
 acpi_os_table_override(struct acpi_table_header * existing_table,
                       struct acpi_table_header ** new_table)
@@ -319,13 +379,18 @@ acpi_os_table_override(struct acpi_table_header * existing_table,
        if (!existing_table || !new_table)
                return AE_BAD_PARAMETER;
 
+       *new_table = NULL;
+
 #ifdef CONFIG_ACPI_CUSTOM_DSDT
        if (strncmp(existing_table->signature, "DSDT", 4) == 0)
                *new_table = (struct acpi_table_header *)AmlCode;
-       else
-               *new_table = NULL;
-#else
-       *new_table = NULL;
+#endif
+#ifdef CONFIG_ACPI_CUSTOM_DSDT_INITRD
+       if (strncmp(existing_table->signature, "DSDT", 4) == 0) {
+               struct acpi_table_header *initrd_table = acpi_find_dsdt_initrd();
+               if (initrd_table)
+                       *new_table = initrd_table;
+       }
 #endif
        return AE_OK;
 }