On Monday 04 February 2008 18:04, Éric Piel wrote: > 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: Eric Piel <eric.piel@xxxxxxxxxxxxxxxx> > > --- > Documentation/dsdt-initrd.txt | 100 +++++++++++++++++++++++++++++++++++++++++ I'd like to move any ACPI-specific documents under a sub-directory, eg. Documentation/acpi/dsdt-initrd.txt > drivers/acpi/Kconfig | 17 +++++++ > drivers/acpi/osl.c | 73 ++++++++++++++++++++++++++++-- > init/initramfs.c | 8 +++- > init/main.c | 7 +++ > 5 files changed, 200 insertions(+), 5 deletions(-) > create mode 100644 Documentation/dsdt-initrd.txt > > diff --git a/Documentation/dsdt-initrd.txt b/Documentation/dsdt-initrd.txt > new file mode 100644 > index 0000000..b2e9460 > --- /dev/null > +++ b/Documentation/dsdt-initrd.txt > @@ -0,0 +1,100 @@ > +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 > > + I'd like to re-write this to largely point to http://www.lesswatts.org/projects/acpi/overridingDSDT.php which I can update. I don't want to maintain two copies of this documentation. > +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 . I'd like to discourage use of http://acpi.sf.net/dsdt except in the extreme cases of permanently broken BIOS that Linux otherwise has no hope of dealing with. > 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 . http://acpica.org/downloads/, but that is on the page above and shouldn't need to be referenced in this file. > +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 ========================== Since we'll have Documentation/acpi/, I think it would be better to have this as a script there rather than a script embedded in a text file. > +#!/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..8607ed3 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>. update this for in-tree location only > + 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..4568a59 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; > + } lets delete the "not found" -- even without the '!' I think it is not what we want to print on effectively 100% of systems in the field. How about simply ACPI: Checking initramfs for custom DSDT. which doesn't imply anything bad when read in dmesg. if something bad happens, it will result in one of the messages below Note that none of the printk's below are checkpatchl.pl clean > + > + 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; I think up here in acpi_os_table_override() is where we should print _which_ override we are using -- to cover the case where there may be one from the kernel and also one from the initrd. If we are using neither, we should print nothing. > } > diff --git a/init/initramfs.c b/init/initramfs.c > index 1db02a0..f2662e2 100644 > --- a/init/initramfs.c > +++ b/init/initramfs.c > @@ -541,7 +541,7 @@ skip: > > #endif > > -static int __init populate_rootfs(void) > +int __init populate_rootfs(void) > { > char *err = unpack_to_rootfs(__initramfs_start, > __initramfs_end - __initramfs_start, 0); > @@ -582,4 +582,10 @@ static int __init populate_rootfs(void) > #endif > 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 f287ca5..7eb1b89 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); > > @@ -643,6 +649,7 @@ asmlinkage void __init start_kernel(void) > > check_bugs(); > > + populate_rootfs(); /* For DSDT override from initramfs */ but this is also done as an initcall, yes? > acpi_early_init(); /* before LAPIC and SMP init */ > > /* Do the rest non-__init'ed, we're now alive */ > - 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
