Hi, IMO, there is already a similar function upstreamed: https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=c85cc81 Could it work for your use case? > From: linux-acpi-owner@xxxxxxxxxxxxxxx [mailto:linux-acpi- > owner@xxxxxxxxxxxxxxx] On Behalf Of Octavian Purdila > Subject: [RFC PATCH 02/10] acpi: install SSDT tables from initrd > > This patch allows loading user defined SSDTs from the first, > uncompressed, initrd. The SSDT aml code must be stored in files under > the /kernel/firmware/acpi/overlay path. > > Signed-off-by: Octavian Purdila <octavian.purdila@xxxxxxxxx> > --- > Documentation/acpi/ssdt-overlays.txt | 94 > ++++++++++++++++++++++++++++++++++++ > drivers/acpi/bus.c | 63 ++++++++++++++++++++++++ > 2 files changed, 157 insertions(+) > create mode 100644 Documentation/acpi/ssdt-overlays.txt > > diff --git a/Documentation/acpi/ssdt-overlays.txt b/Documentation/acpi/ssdt- > overlays.txt > new file mode 100644 > index 0000000..a94c3f9 > --- /dev/null > +++ b/Documentation/acpi/ssdt-overlays.txt > @@ -0,0 +1,94 @@ > + > +In order to support ACPI open-ended hardware configurations (e.g. > development > +boards) we need a way to augment the ACPI configuration provided by the > firmware > +image. A common example is connecting sensors on I2C / SPI buses on > development > +boards. > + > +Although this can be accomplished by creating a kernel platform driver or > +recompiling the firmware image with updated ACPI tables, neither is practical: > +the former proliferates board specific kernel code while the latter requires > +access to firmware tools which are often not publicly available. > + > +Because ACPI supports external references in AML code a more practical > +way to augment firmware ACPI configuration is by dynamically loading > +user defined SSDT tables that contain the board specific information. > + > +For example, to enumerate a Bosch BMA222E accelerometer on the I2C bus > of the > +Minnowboard MAX development board exposed via the LSE connector [1], > the > +following ASL code can be used: > + > +DefinitionBlock ("minnowmax.aml", "SSDT", 1, "Vendor", "Accel", 0x00000003) > +{ > + External (\_SB.I2C6, DeviceObj) > + > + Scope (\_SB.I2C6) > + { > + Device (STAC) > + { > + Name (_ADR, Zero) > + Name (_HID, "BMA222E") > + > + Method (_CRS, 0, Serialized) > + { > + Name (RBUF, ResourceTemplate () > + { > + I2cSerialBus (0x0018, ControllerInitiated, 0x00061A80, > + AddressingMode7Bit, "\\_SB.I2C6", 0x00, > + ResourceConsumer, ,) > + GpioInt (Edge, ActiveHigh, Exclusive, PullDown, 0x0000, > + "\\_SB.GPO2", 0x00, ResourceConsumer, , ) > + { // Pin list > + 0 > + } > + }) > + Return (RBUF) > + } > + } > + } > +} > + > +which can then be compiled to AML binary format: > + > +$ iasl minnowmax.asl > + > +Intel ACPI Component Architecture > +ASL Optimizing Compiler version 20140214-64 [Mar 29 2014] > +Copyright (c) 2000 - 2014 Intel Corporation > + > +ASL Input: minnomax.asl - 30 lines, 614 bytes, 7 keywords > +AML Output: minnowmax.aml - 165 bytes, 6 named objects, 1 executable > opcodes > + > +[1] > http://wiki.minnowboard.org/MinnowBoard_MAX#Low_Speed_Expansion_Co > nnector_.28Top.29 > + > +The resulting AML code can then be loaded by the kernel using one of the > methods > +below. > + > +== Loading ACPI SSDTs from initrd == > + > +This option allows loading of user defined SSDTs from initrd and it is useful > +when the system does not support EFI or when there is not enough EFI > storage. > + > +It works in a similar way with initrd based ACPI tables overrides: SSDT aml > code > +must be placed in the first, uncompressed, initrd under the > +"kernel/firmware/acpi/overlay" path. We use a different path than the initrd > +tables override to avoid conflicts with the override feature. > + > +Multiple files can be used and this will translate in loading multiple > +tables. Only tables with the SSDT signature will be loaded. > + > +Here is an example: > + > +# Add the raw ACPI tables to an uncompressed cpio archive. > +# They must be put into a /kernel/firmware/acpi/overlay directory inside the > +# cpio archive. > +# The uncompressed cpio archive must be the first. > +# Other, typically compressed cpio archives, must be > +# concatenated on top of the uncompressed one. > +mkdir -p kernel/firmware/acpi > +cp ssdt.aml kernel/firmware/acpi > + > +# Create the uncompressed cpio archive and concatenate the original initrd > +# on top: > +find kernel | cpio -H newc --create > /boot/instrumented_initrd > +cat /boot/initrd >>/boot/instrumented_initrd > + > diff --git a/drivers/acpi/bus.c b/drivers/acpi/bus.c > index 891c42d..5e0d076 100644 > --- a/drivers/acpi/bus.c > +++ b/drivers/acpi/bus.c > @@ -37,9 +37,14 @@ > #include <acpi/apei.h> > #include <linux/dmi.h> > #include <linux/suspend.h> > +#include <linux/initrd.h> > +#include <linux/earlycpio.h> > > #include "internal.h" > > +#undef pr_fmt > +#define pr_fmt(fmt) "ACPI: " fmt > + > #define _COMPONENT ACPI_BUS_COMPONENT > ACPI_MODULE_NAME("bus"); > > @@ -863,6 +868,62 @@ static int __init acpi_bus_init_irq(void) > return 0; > } > > +void __init acpi_load_initrd_ssdts(void) > +{ > + void *data = (void *)initrd_start; > + int size = initrd_end - initrd_start; > + const char *path = "kernel/firmware/acpi/overlay"; > + long offset = 0; > + struct cpio_data file; > + struct acpi_table_header *header; > + void *table; > + acpi_status status; > + > + while (true) { > + file = find_cpio_data(path, data, size, &offset); > + if (!file.data) > + break; > + > + data += offset; > + size -= offset; > + > + if (file.size < sizeof(struct acpi_table_header)) { > + pr_err("initrd table smaller than ACPI header > [%s%s]\n", > + path, file.name); > + continue; > + } > + > + header = file.data; > + > + if (file.size != header->length) { > + pr_err("initrd file / table length mismatch [%s%s]\n", > + path, file.name); > + continue; > + } > + > + if (memcmp(header->signature, ACPI_SIG_SSDT, 4)) { > + pr_warn("skipping non-SSDT initrd table [%s%s]\n", > + path, file.name); > + continue; > + } > + > + table = kmemdup(file.data, file.size, GFP_KERNEL); > + if (!table) > + continue; > + > + status = acpi_install_table((uintptr_t)table, 0); > + if (ACPI_FAILURE(status)) { > + pr_err("failed to install SSDT from initrd [%s%s]\n", > + path, file.name); > + kfree(table); > + } > + > + pr_info("installed SSDT table found in initrd [%s%s][0x%x]\n", > + path, file.name, header->length); > + add_taint(TAINT_OVERLAY_ACPI_TABLE, LOCKDEP_STILL_OK); > + } > +} > + [Lv Zheng] I can see that this is so similar to the acpi_initrd_initialize_tables() which is in the drivers/acpi/osl.c. Please check. Thanks and best regards -Lv > /** > * acpi_early_init - Initialize ACPICA and populate the ACPI namespace. > * > @@ -911,6 +972,8 @@ void __init acpi_early_init(void) > goto error0; > } > > + acpi_load_initrd_ssdts(); > + > status = acpi_load_tables(); > if (ACPI_FAILURE(status)) { > printk(KERN_ERR PREFIX > -- > 1.9.1 > > -- > 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 -- 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
