ACPI: basic initramfs DSDT override support
The basics of DSDT from initramfs. In case this option is selected, populate_rootfs() is called a bit earlier to have the initramfs content available during ACPI initialization. This is a very similar path to the one available at http://gaugusch.at/kernel.shtml but with some update in the documentation, default set to No and the change of populate_rootfs() the "Jeff Mahony way" (which avoids reading the initramfs twice). Signed-off-by: Thomas Renninger <trenn@suse.de> Signed-off-by: Eric Piel <eric.piel@tremplin-utc.net> Signed-off-by: Len Brown <len.brown@intel.com>
This commit is contained in:
Markus Gaugusch
Len Brown
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488b5ec871
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ACPI Custom DSDT read from initramfs
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2003 by Markus Gaugusch < dsdt at gaugusch dot at >
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Special thanks go to Thomas Renninger from SuSE, who updated the patch for
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2.6.0 and later modified it to read inside initramfs
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2004 - 2008 maintained by Eric Piel < eric dot piel at tremplin-utc dot net >
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This option is intended for people who would like to hack their DSDT and don't
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want to recompile their kernel after every change. It can also be useful to
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distros which offers pre-compiled kernels and want to allow their users to use
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a modified DSDT. In the Kernel config, enable the initial RAM filesystem
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support (in General Setup) and enable ACPI_CUSTOM_DSDT_INITRD at the ACPI
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options (General Setup|ACPI Support|Read Custom DSDT from initramfs).
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A custom DSDT (Differentiated System Description Table) is useful when your
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computer uses ACPI but problems occur due to broken implementation. Typically,
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your computer works but there are some troubles with the hardware detection or
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the power management. You can check that troubles come from errors in the DSDT by
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activating the ACPI debug option and reading the logs. This table is provided
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by the BIOS, therefore it might be a good idea to check for BIOS update on your
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vendor website before going any further. Errors are often caused by vendors
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testing their hardware only with Windows or because there is code which is
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executed only on a specific OS with a specific version and Linux hasn't been
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considered during the development.
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Before you run away from customising your DSDT, you should note that already
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corrected tables are available for a fair amount of computers on this web-page:
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http://acpi.sf.net/dsdt . Be careful though, to work correctly a DSDT has to
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match closely the hardware, including the amount of RAM, the frequency of the
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processor and the PCI cards present! If you are part of the unluckies who
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cannot find their hardware in this database, you can modify your DSDT by
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yourself. This process is less painful than it sounds. Download the Intel ASL
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compiler/decompiler at http://www.intel.com/technology/IAPC/acpi/downloads.htm .
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As root, you then have to dump your DSDT and decompile it. By using the
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compiler messages as well as the kernel ACPI debug messages and the reference
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book (available at the Intel website and also at http://www.acpi.info), it is
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quite easy to obtain a fully working table.
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Once your new DSDT is ready you'll have to add it to an initramfs so that the
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kernel can read the table at the very beginning of the boot. As the file has to
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be accessed very early during the boot process the initramfs has to be an
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initramfs. The file is contained into the initramfs under the name /DSDT.aml .
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To obtain such an initramfs, you might have to modify your initramfs script or
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you can add it later to the initramfs with the script appended to this
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document. The command will look like:
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initramfs-add-dsdt initramfs.img my-dsdt.aml
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In case you don't use any initramfs, the possibilities you have are to either
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start using one (try mkinitrd or yaird), or use the "Include Custom DSDT"
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configure option to directly include your DSDT inside the kernel.
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The message "Looking for DSDT in initramfs..." will tell you if the DSDT was
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found or not. If you need to update your DSDT, generate a new initramfs and
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perform the steps above. Don't forget that with Lilo, you'll have to re-run it.
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====================== Here starts initramfs-add-dsdt ==========================
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#!/bin/bash
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# Adds a DSDT file to the initrd (if it's an initramfs)
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# first argument is the name of archive
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# second argument is the name of the file to add
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# The file will be copied as /DSDT.aml
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# 20060126: fix "Premature end of file" with some old cpio (Roland Robic)
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# 20060205: this time it should really work
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# check the arguments
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if [ $# -ne 2 ]; then
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program_name=$(basename $0)
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echo "\
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$program_name: too few arguments
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Usage: $program_name initrd-name.img DSDT-to-add.aml
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Adds a DSDT file to an initrd (in initramfs format)
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initrd-name.img: filename of the initrd in initramfs format
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DSDT-to-add.aml: filename of the DSDT file to add
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" 1>&2
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exit 1
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fi
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# we should check it's an initramfs
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tempcpio=$(mktemp -d)
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# cleanup on exit, hangup, interrupt, quit, termination
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trap 'rm -rf $tempcpio' 0 1 2 3 15
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# extract the archive
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gunzip -c "$1" > "$tempcpio"/initramfs.cpio || exit 1
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# copy the DSDT file at the root of the directory so that we can call it "/DSDT.aml"
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cp -f "$2" "$tempcpio"/DSDT.aml
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# add the file
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cd "$tempcpio"
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(echo DSDT.aml | cpio --quiet -H newc -o -A -O "$tempcpio"/initramfs.cpio) || exit 1
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cd "$OLDPWD"
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# re-compress the archive
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gzip -c "$tempcpio"/initramfs.cpio > "$1"
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@ -274,6 +274,23 @@ config ACPI_CUSTOM_DSDT_FILE
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Enter the full path name to the file which includes the AmlCode
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declaration.
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config ACPI_CUSTOM_DSDT_INITRD
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bool "Read Custom DSDT from initramfs"
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depends on BLK_DEV_INITRD
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default n
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help
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The DSDT (Differentiated System Description Table) often needs to be
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overridden because of broken BIOS implementations. If this feature is
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activated you will be able to provide a customized DSDT by adding it
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to your initramfs. If your mkinitrd tool does not support this feature
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a script is provided in the documentation. For more details see
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<file:Documentation/dsdt-initrd.txt> or <http://gaugusch.at/kernel.shtml>.
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If there is no table found, it will fall-back to the custom DSDT
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in-kernel (if activated) or to the DSDT from the BIOS.
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Even if you do not need a new one at the moment, you may want to use a
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better DSDT later. It is safe to say Y here.
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config ACPI_BLACKLIST_YEAR
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int "Disable ACPI for systems before Jan 1st this year" if X86_32
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default 0
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@ -312,6 +312,66 @@ acpi_os_predefined_override(const struct acpi_predefined_names *init_val,
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return AE_OK;
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}
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#ifdef CONFIG_ACPI_CUSTOM_DSDT_INITRD
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struct acpi_table_header *acpi_find_dsdt_initrd(void)
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{
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struct file *firmware_file;
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mm_segment_t oldfs;
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unsigned long len, len2;
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struct acpi_table_header *dsdt_buffer, *ret = NULL;
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struct kstat stat;
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char *ramfs_dsdt_name = "/DSDT.aml";
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printk(KERN_INFO PREFIX "Looking for DSDT in initramfs... ");
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/*
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* Never do this at home, only the user-space is allowed to open a file.
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* The clean way would be to use the firmware loader. But this code must be run
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* before there is any userspace available. So we need a static/init firmware
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* infrastructure, which doesn't exist yet...
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*/
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if (vfs_stat(ramfs_dsdt_name, &stat) < 0) {
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printk("not found.\n");
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return ret;
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}
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len = stat.size;
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/* check especially against empty files */
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if (len <= 4) {
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printk("error, file is too small: only %lu bytes.\n", len);
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return ret;
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}
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firmware_file = filp_open(ramfs_dsdt_name, O_RDONLY, 0);
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if (IS_ERR(firmware_file)) {
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printk("error, could not open file %s.\n", ramfs_dsdt_name);
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return ret;
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}
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dsdt_buffer = ACPI_ALLOCATE(len);
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if (!dsdt_buffer) {
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printk("error when allocating %lu bytes of memory.\n", len);
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goto err;
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}
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oldfs = get_fs();
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set_fs(KERNEL_DS);
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len2 = vfs_read(firmware_file, (char __user *)dsdt_buffer, len, &firmware_file->f_pos);
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set_fs(oldfs);
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if (len2 < len) {
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printk("error trying to read %lu bytes from %s.\n", len, ramfs_dsdt_name);
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ACPI_FREE(dsdt_buffer);
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goto err;
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}
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printk("successfully read %lu bytes from %s.\n", len, ramfs_dsdt_name);
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ret = dsdt_buffer;
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err:
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filp_close(firmware_file, NULL);
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return ret;
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}
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#endif
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acpi_status
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acpi_os_table_override(struct acpi_table_header * existing_table,
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struct acpi_table_header ** new_table)
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@ -319,13 +379,18 @@ acpi_os_table_override(struct acpi_table_header * existing_table,
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if (!existing_table || !new_table)
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return AE_BAD_PARAMETER;
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*new_table = NULL;
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#ifdef CONFIG_ACPI_CUSTOM_DSDT
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if (strncmp(existing_table->signature, "DSDT", 4) == 0)
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*new_table = (struct acpi_table_header *)AmlCode;
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else
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*new_table = NULL;
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#else
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*new_table = NULL;
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#endif
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#ifdef CONFIG_ACPI_CUSTOM_DSDT_INITRD
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if (strncmp(existing_table->signature, "DSDT", 4) == 0) {
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struct acpi_table_header *initrd_table = acpi_find_dsdt_initrd();
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if (initrd_table)
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*new_table = initrd_table;
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}
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#endif
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return AE_OK;
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}
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@ -538,7 +538,7 @@ skip:
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initrd_end = 0;
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}
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static int __init populate_rootfs(void)
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int __init populate_rootfs(void)
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{
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char *err = unpack_to_rootfs(__initramfs_start,
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__initramfs_end - __initramfs_start, 0);
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@ -577,4 +577,10 @@ static int __init populate_rootfs(void)
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}
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return 0;
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}
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#ifndef CONFIG_ACPI_CUSTOM_DSDT_INITRD
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/*
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* if this option is enabled, populate_rootfs() is called _earlier_ in the
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* boot sequence. This insures that the ACPI initialisation can find the file.
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*/
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rootfs_initcall(populate_rootfs);
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#endif
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@ -102,6 +102,12 @@ static inline void mark_rodata_ro(void) { }
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extern void tc_init(void);
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#endif
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#ifdef CONFIG_ACPI_CUSTOM_DSDT_INITRD
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extern int populate_rootfs(void);
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#else
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static inline void populate_rootfs(void) {}
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#endif
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enum system_states system_state;
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EXPORT_SYMBOL(system_state);
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@ -648,6 +654,7 @@ asmlinkage void __init start_kernel(void)
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check_bugs();
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populate_rootfs(); /* For DSDT override from initramfs */
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acpi_early_init(); /* before LAPIC and SMP init */
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/* Do the rest non-__init'ed, we're now alive */
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