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ACPI: basic initramfs DSDT override support

Browse source 
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 <[email protected]>
Signed-off-by: Eric Piel <[email protected]>
Signed-off-by: Len Brown <[email protected]>
This commit is contained in:
Markus Gaugusch 2008-02-05 00:04:06 +01:00 • committed by Len Brown
commit 71fc47a9ad
5 changed files with 199 additions and 5 deletions
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17
drivers/acpi/Kconfig
View file

@ -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

73
drivers/acpi/osl.c
View file

@ -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;
}