linux-kernel - Re: [PATCH] ACPI / tables: table upgrade from built-in initrd

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Date:   Mon, 17 Dec 2018 10:03:46 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     shunyong.yang@...-semitech.com
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        yu.zheng@...-semitech.com
Subject: Re: [PATCH] ACPI / tables: table upgrade from built-in initrd

On Mon, Dec 17, 2018 at 3:40 AM Shunyong Yang
<shunyong.yang@...-semitech.com> wrote:
>
> In some scenario, we need to build initrd with kernel in a single image.
> This can simplify system deployment process by downloading the whole system
> once, such as in IC verification.
>
> This patch adds support to upgrade ACPI tables from built-in initrd.

What do you mean by "upgrade"?

>
> Cc: Joey Zheng <yu.zheng@...-semitech.com>
> Signed-off-by: Shunyong Yang <shunyong.yang@...-semitech.com>
> ---
>  drivers/acpi/Kconfig   |  9 +++++++++
>  drivers/acpi/tables.c  | 12 ++++++++++--
>  include/linux/initrd.h |  3 +++
>  3 files changed, 22 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
> index 7cea769c37df..30976496fe77 100644
> --- a/drivers/acpi/Kconfig
> +++ b/drivers/acpi/Kconfig
> @@ -357,6 +357,15 @@ config ACPI_TABLE_UPGRADE
>           initrd, therefore it's safe to say Y.
>           See Documentation/acpi/initrd_table_override.txt for details
>
> +config ACPI_TABLE_UPGRADE_VIA_BUILTIN_INITRD
> +       bool "Upgrade ACPI tables from built-in initrd"
> +       depends on ACPI_TABLE_UPGRADE
> +       depends on INITRAMFS_SOURCE!="" && INITRAMFS_COMPRESSION=""
> +       def_bool n
> +       help
> +         This option provides functionality to upgrade arbitrary ACPI tables
> +         from built-in uncompressed initrd.
> +
>  config ACPI_DEBUG
>         bool "Debug Statements"
>         help
> diff --git a/drivers/acpi/tables.c b/drivers/acpi/tables.c
> index 61203eebf3a1..88e3a34443da 100644
> --- a/drivers/acpi/tables.c
> +++ b/drivers/acpi/tables.c
> @@ -473,14 +473,22 @@ static u8 __init acpi_table_checksum(u8 *buffer, u32 length)
>
>  void __init acpi_table_upgrade(void)
>  {
> -       void *data = (void *)initrd_start;
> -       size_t size = initrd_end - initrd_start;
> +       void *data;
> +       size_t size;
>         int sig, no, table_nr = 0, total_offset = 0;
>         long offset = 0;
>         struct acpi_table_header *table;
>         char cpio_path[32] = "kernel/firmware/acpi/";
>         struct cpio_data file;
>
> +       if (IS_ENABLED(CONFIG_ACPI_TABLE_UPGRADE_VIA_BUILTIN_INITRD)) {
> +               data = __initramfs_start;
> +               size = __initramfs_size;
> +       } else {
> +               data = (void *)initrd_start;
> +               size = initrd_end - initrd_start;
> +       }
> +
>         if (data == NULL || size == 0)
>                 return;
>
> diff --git a/include/linux/initrd.h b/include/linux/initrd.h
> index 84b423044088..02d94aae54c7 100644
> --- a/include/linux/initrd.h
> +++ b/include/linux/initrd.h
> @@ -22,3 +22,6 @@
>  extern void free_initrd_mem(unsigned long, unsigned long);
>
>  extern unsigned int real_root_dev;
> +
> +extern char __initramfs_start[];
> +extern unsigned long __initramfs_size;
> --
> 1.8.3.1
>