RE: [RFC PATCH 02/10] acpi: install SSDT tables from initrd

["Zheng, Lv" <lv.zheng@intel.com>]

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@vger.kernel.org [mailto:linux-acpi-
> owner@vger.kernel.org] 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@intel.com>
> ---
>  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
> 
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