From: Markus Gaugusch <dsdt@xxxxxxxxxxx> 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@xxxxxxx> Signed-off-by: Eric Piel <eric.piel@xxxxxxxxxxxxxxxx> Signed-off-by: Len Brown <len.brown@xxxxxxxxx> --- Documentation/acpi/dsdt-initrd.txt | 99 ++++++++++++++++++++++++++++++++++++ drivers/acpi/Kconfig | 17 ++++++ drivers/acpi/osl.c | 73 +++++++++++++++++++++++++-- init/initramfs.c | 8 +++- init/main.c | 7 +++ 5 files changed, 199 insertions(+), 5 deletions(-) create mode 100644 Documentation/acpi/dsdt-initrd.txt diff --git a/Documentation/acpi/dsdt-initrd.txt b/Documentation/acpi/dsdt-initrd.txt new file mode 100644 index 0000000..7360433 --- /dev/null +++ b/Documentation/acpi/dsdt-initrd.txt @@ -0,0 +1,99 @@ +ACPI Custom DSDT read from initramfs + +2003 by Markus Gaugusch < dsdt at gaugusch dot at > +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 - 2008 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 General Setup) and enable ACPI_CUSTOM_DSDT_INITRD at the ACPI +options (General Setup|ACPI Support|Read Custom DSDT from initramfs). + +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 . Be careful though, to work correctly a DSDT has to +match closely the hardware, including the amount of RAM, the frequency of the +processor and the PCI cards present! 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 initramfs 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 initramfs has to be an +initramfs. The file is contained into the initramfs under the name /DSDT.aml . +To obtain such an initramfs, you might have to modify your initramfs script or +you can add it later to the initramfs with the script appended to this +document. The command will look like: +initramfs-add-dsdt initramfs.img my-dsdt.aml + +In case you don't use any initramfs, 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 initramfs and +perform the steps above. Don't forget that with Lilo, you'll have to re-run it. + + +====================== Here starts initramfs-add-dsdt ========================== +#!/bin/bash +# Adds a DSDT file to the initrd (if it's an initramfs) +# first argument is the name of archive +# second argument 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 --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig index ccf6ea9..0442ae1 100644 --- a/drivers/acpi/Kconfig +++ b/drivers/acpi/Kconfig @@ -274,6 +274,23 @@ 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 n + 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. If your mkinitrd tool does not support this feature + a script is provided in the documentation. For more details see + <file:Documentation/dsdt-initrd.txt> or <http://gaugusch.at/kernel.shtml>. + If there is no table found, it will fall-back 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 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 --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c index e53fb51..131936e 100644 --- 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; } diff --git a/init/initramfs.c b/init/initramfs.c index d53fee8..c0b1e05 100644 --- a/init/initramfs.c +++ b/init/initramfs.c @@ -538,7 +538,7 @@ skip: initrd_end = 0; } -static int __init populate_rootfs(void) +int __init populate_rootfs(void) { char *err = unpack_to_rootfs(__initramfs_start, __initramfs_end - __initramfs_start, 0); @@ -577,4 +577,10 @@ static int __init populate_rootfs(void) } return 0; } +#ifndef CONFIG_ACPI_CUSTOM_DSDT_INITRD +/* + * if this option is enabled, populate_rootfs() is called _earlier_ in the + * boot sequence. This insures that the ACPI initialisation can find the file. + */ rootfs_initcall(populate_rootfs); +#endif diff --git a/init/main.c b/init/main.c index c691f5f..2a78932 100644 --- a/init/main.c +++ b/init/main.c @@ -102,6 +102,12 @@ static inline void mark_rodata_ro(void) { } extern void tc_init(void); #endif +#ifdef CONFIG_ACPI_CUSTOM_DSDT_INITRD +extern int populate_rootfs(void); +#else +static inline void populate_rootfs(void) {} +#endif + enum system_states system_state; EXPORT_SYMBOL(system_state); @@ -648,6 +654,7 @@ asmlinkage void __init start_kernel(void) check_bugs(); + populate_rootfs(); /* For DSDT override from initramfs */ acpi_early_init(); /* before LAPIC and SMP init */ /* Do the rest non-__init'ed, we're now alive */ -- 1.5.4.23.gef5b9 - To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
