Date:	Fri, 01 Dec 2006 13:36:19 -0500
From:	Ben Collins <ben.collins@...ntu.com>
To:	linux-kernel@...r.kernel.org
Cc:	Eric Piel <eric.piel@...mplin-utc>
Subject: [RFC] Include ACPI DSDT from INITRD patch into mainline

I'd be willing to bet that most distros have this patch in their kernel.
One of those things we can't really live without.

What I haven't understood is why it isn't included in the mainline
kernel yet. There's enough kernel hackers out there using this that I
doubt it will get stale or broken for very long.

I'm willing to do the grunt work to get it suitable.

Patch attached for convenience.

diff -urpN -X linux-2.6.18/Documentation/dontdiff linux-2.6.18.bak/Documentation/dsdt-initrd.txt linux-2.6.18/Documentation/dsdt-initrd.txt
--- linux-2.6.18.bak/Documentation/dsdt-initrd.txt	1970-01-01 01:00:00.000000000 +0100
+++ linux-2.6.18/Documentation/dsdt-initrd.txt	2006-08-12 11:15:13.000000000 +0200
@@ -0,0 +1,98 @@
+ACPI Custom DSDT read from initramfs
+
+2003 by Markuss Gaugusch < dsdt at gaugusch dot org >
+Special thanks go to Thomas Renninger from SuSE, who updated the patch for
+2.6.0 and later modified it to read inside initramfs
+2004 - 2006 maintained by Eric Piel < eric dot piel at tremplin-utc dot net >
+
+This option is intended for people who would like to hack their DSDT and don't want
+to recompile their kernel after every change. It can also be useful to distros
+which offers pre-compiled kernels and want to allow their users to use a
+modified DSDT. In the Kernel config, enable the initial RAM filesystem support
+(in Device Drivers|Block Devices) and enable ACPI_CUSTOM_DSDT_INITRD at the ACPI
+options (General Setup|ACPI Support|Read custom DSDT from initrd).
+
+A custom DSDT (Differentiated System Description Table) is useful when your
+computer uses ACPI but problems occur due to broken implementation. Typically,
+your computer works but there are some troubles with the hardware detection or
+the power management. You can check that troubles come from errors in the DSDT by
+activating the ACPI debug option and reading the logs. This table is provided
+by the BIOS, therefore it might be a good idea to check for BIOS update on your
+vendor website before going any further. Errors are often caused by vendors
+testing their hardware only with Windows or because there is code which is
+executed only on a specific OS with a specific version and Linux hasn't been
+considered during the development.
+
+Before you run away from customising your DSDT, you should note that already
+corrected tables are available for a fair amount of computers on this web-page:
+http://acpi.sf.net/dsdt . If you are part of the unluckies who cannot find
+their hardware in this database, you can modify your DSDT by yourself. This
+process is less painful than it sounds. Download the Intel ASL 
+compiler/decompiler at http://www.intel.com/technology/IAPC/acpi/downloads.htm .
+As root, you then have to dump your DSDT and decompile it. By using the
+compiler messages as well as the kernel ACPI debug messages and the reference book
+(available at the Intel website and also at http://www.acpi.info), it is quite
+easy to obtain a fully working table.
+
+Once your new DSDT is ready you'll have to add it to an initrd so that the
+kernel can read the table at the very beginning of the boot. As the file has
+to be accessed very early during the boot process the initrd has to be an
+initramfs. The file is contained into the initramfs under the name /DSDT.aml .
+To obtain such an initrd, you might have to modify your mkinitrd script or you
+can add it later to the initrd with the script appended to this document. The
+command will look like:
+initrd-add-dsdt initrd.img my-dsdt.aml
+
+In case you don't use any initrd, the possibilities you have are to either start
+using one (try mkinitrd or yaird), or use the "Include Custom DSDT" configure
+option to directly include your DSDT inside the kernel.
+
+The message "Looking for DSDT in initramfs..." will tell you if the DSDT was
+found or not. If you need to update your DSDT, generate a new initrd and
+perform the steps above. Don't forget that with Lilo, you'll have to re-run it.
+
+
+======================= Here starts initrd-add-dsdt ===============================
+#!/bin/bash
+# Adds a DSDT file to the initrd (if it's an initramfs)
+# first argument is the name of archive
+# second argurment is the name of the file to add
+# The file will be copied as /DSDT.aml
+
+# 20060126: fix "Premature end of file" with some old cpio (Roland Robic)
+# 20060205: this time it should really work
+
+# check the arguments
+if [ $# -ne 2 ]; then
+	program_name=$(basename $0)
+	echo "\
+$program_name: too few arguments
+Usage: $program_name initrd-name.img DSDT-to-add.aml
+Adds a DSDT file to an initrd (in initramfs format)
+
+  initrd-name.img: filename of the initrd in initramfs format
+  DSDT-to-add.aml: filename of the DSDT file to add
+  " 1>&2
+    exit 1
+fi
+
+# we should check it's an initramfs
+
+tempcpio=$(mktemp -d)
+# cleanup on exit, hangup, interrupt, quit, termination
+trap 'rm -rf $tempcpio' 0 1 2 3 15
+
+# extract the archive
+gunzip -c "$1" > "$tempcpio"/initramfs.cpio || exit 1
+
+# copy the DSDT file at the root of the directory so that we can call it "/DSDT.aml"
+cp -f "$2" "$tempcpio"/DSDT.aml
+
+# add the file
+cd "$tempcpio"
+(echo DSDT.aml | cpio --quiet -H newc -o -A -O "$tempcpio"/initramfs.cpio) || exit 1
+cd "$OLDPWD"
+
+# re-compress the archive
+gzip -c "$tempcpio"/initramfs.cpio > "$1"
+
diff -urpN -X linux-2.6.18/Documentation/dontdiff linux-2.6.18.bak/drivers/acpi/Kconfig linux-2.6.18/drivers/acpi/Kconfig
--- linux-2.6.18.bak/drivers/acpi/Kconfig	2006-08-12 11:14:05.000000000 +0200
+++ linux-2.6.18/drivers/acpi/Kconfig	2006-08-12 11:15:13.000000000 +0200
@@ -264,6 +264,23 @@ config ACPI_CUSTOM_DSDT_FILE
 	  Enter the full path name to the file which includes the AmlCode
 	  declaration.
 
+config ACPI_CUSTOM_DSDT_INITRD
+	bool "Read Custom DSDT from initramfs"
+	depends on BLK_DEV_INITRD
+	default y
+	help
+	  The DSDT (Differentiated System Description Table) often needs to be
+	  overridden because of broken BIOS implementations. If this feature is
+	  activated you will be able to provide a customized DSDT by adding it
+	  to your initramfs.  For now you need to use a special mkinitrd tool.
+	  For more details see <file:Documentation/dsdt-initrd.txt> or 
+	  <http://gaugusch.at/kernel.shtml>. If there is no table found, it 
+	  will fallback to the custom DSDT in-kernel (if activated) or to the
+	  DSDT from the BIOS.
+
+	  Even if you do not need a new one at the moment, you may want to use a
+	  better implemented DSDT later. It is safe to say Y here.
+
 config ACPI_BLACKLIST_YEAR
 	int "Disable ACPI for systems before Jan 1st this year" if X86_32
 	default 0
diff -urpN -X linux-2.6.18/Documentation/dontdiff linux-2.6.18.bak/drivers/acpi/osl.c linux-2.6.18/drivers/acpi/osl.c
--- linux-2.6.18.bak/drivers/acpi/osl.c	2006-08-12 11:14:05.000000000 +0200
+++ linux-2.6.18/drivers/acpi/osl.c	2006-08-12 11:16:08.000000000 +0200
@@ -69,6 +69,10 @@ extern char line_buf[80];
 int acpi_specific_hotkey_enabled = TRUE;
 EXPORT_SYMBOL(acpi_specific_hotkey_enabled);
 
+#ifdef CONFIG_ACPI_CUSTOM_DSDT_INITRD
+int acpi_must_unregister_table = FALSE;
+#endif
+
 static unsigned int acpi_irq_irq;
 static acpi_osd_handler acpi_irq_handler;
 static void *acpi_irq_context;
@@ -219,6 +223,67 @@ acpi_os_predefined_override(const struct
 	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;
+	/* maybe this could be an argument on the cmd line, but let's keep it simple for now */
+	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("error, file %s not found.\n", ramfs_dsdt_name);
+		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)
@@ -226,13 +291,20 @@ acpi_os_table_override(struct acpi_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;
+			acpi_must_unregister_table = TRUE;
+		}
+	}
 #endif
 	return AE_OK;
 }
diff -urpN -X linux-2.6.18/Documentation/dontdiff linux-2.6.18.bak/drivers/acpi/tables/tbget.c linux-2.6.18/drivers/acpi/tables/tbget.c
--- linux-2.6.18.bak/drivers/acpi/tables/tbget.c	2006-08-12 11:14:05.000000000 +0200
+++ linux-2.6.18/drivers/acpi/tables/tbget.c	2006-08-12 11:15:27.000000000 +0200
@@ -278,6 +278,14 @@ acpi_tb_table_override(struct acpi_table
 	address.pointer.logical = new_table;
 
 	status = acpi_tb_get_this_table(&address, new_table, table_info);
+
+#ifdef CONFIG_ACPI_CUSTOM_DSDT_INITRD
+	if (acpi_must_unregister_table) {
+		ACPI_FREE(new_table);
+		acpi_must_unregister_table = FALSE;
+	}
+#endif
+
 	if (ACPI_FAILURE(status)) {
 		ACPI_EXCEPTION((AE_INFO, status, "Could not copy ACPI table"));
 		return_ACPI_STATUS(status);
diff -urpN -X linux-2.6.18/Documentation/dontdiff linux-2.6.18.bak/include/acpi/acpiosxf.h linux-2.6.18/include/acpi/acpiosxf.h
--- linux-2.6.18.bak/include/acpi/acpiosxf.h	2006-08-12 11:14:05.000000000 +0200
+++ linux-2.6.18/include/acpi/acpiosxf.h	2006-08-12 11:15:13.000000000 +0200
@@ -95,6 +95,10 @@ acpi_status
 acpi_os_table_override(struct acpi_table_header *existing_table,
 		       struct acpi_table_header **new_table);
 
+#ifdef CONFIG_ACPI_CUSTOM_DSDT_INITRD
+extern int acpi_must_unregister_table;
+#endif
+
 /*
  * Spinlock primitives
  */
diff -urpN -X linux-2.6.18/Documentation/dontdiff linux-2.6.18.bak/init/main.c linux-2.6.18/init/main.c
--- linux-2.6.18.bak/init/main.c	2006-08-12 11:14:05.000000000 +0200
+++ linux-2.6.18/init/main.c	2006-08-12 11:15:13.000000000 +0200
@@ -581,8 +581,6 @@ asmlinkage void __init start_kernel(void
 
 	check_bugs();
 
-	acpi_early_init(); /* before LAPIC and SMP init */
-
 	/* Do the rest non-__init'ed, we're now alive */
 	rest_init();
 }
@@ -699,6 +697,14 @@ static int init(void * unused)
 	 */
 	child_reaper = current;
 
+ 	/*
+ 	 * Do this before initcalls, because some drivers want to access
+ 	 * firmware files.
+ 	 */
+ 	populate_rootfs();
+ 
+ 	acpi_early_init(); /* before LAPIC and SMP init */
+
 	smp_prepare_cpus(max_cpus);
 
 	do_pre_smp_initcalls();
@@ -708,12 +714,6 @@ static int init(void * unused)
 
 	cpuset_init_smp();
 
-	/*
-	 * Do this before initcalls, because some drivers want to access
-	 * firmware files.
-	 */
-	populate_rootfs();
-
 	do_basic_setup();
 
 	/*

-
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