linux-kernel - Re: [PATCH] of: document /sys/firmware/fdt

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Date:   Thu, 29 Jun 2017 14:28:41 +0100
From:   Grant Likely <grant.likely@...retlab.ca>
To:     Frank Rowand <frowand.list@...il.com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] of: document /sys/firmware/fdt

On Wed, Jun 14, 2017 at 5:20 AM,  <frowand.list@...il.com> wrote:
> From: Frank Rowand <frank.rowand@...y.com>
>
> Add ABI documentation for /sys/firmware/fdt
>
> Update contact for /sys/firmware/devicetree/* to include mail list
>
> Signed-off-by: Frank Rowand <frank.rowand@...y.com>

Acked-by: Grant Likely <grant.likely@....com>

(Apologies for acking from a different address. My ARM email isn't yet
set up to play nice on mailing lists.)

g.

> ---
>  Documentation/ABI/testing/sysfs-firmware-ofw | 27 ++++++++++++++++++++++++++-
>  1 file changed, 26 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/ABI/testing/sysfs-firmware-ofw b/Documentation/ABI/testing/sysfs-firmware-ofw
> index f562b188e71d..8e700db6c295 100644
> --- a/Documentation/ABI/testing/sysfs-firmware-ofw
> +++ b/Documentation/ABI/testing/sysfs-firmware-ofw
> @@ -1,6 +1,6 @@
>  What:          /sys/firmware/devicetree/*
>  Date:          November 2013
> -Contact:       Grant Likely <grant.likely@...aro.org>
> +Contact:       Grant Likely <grant.likely@...aro.org>, devicetree@...r.kernel.org
>  Description:
>                 When using OpenFirmware or a Flattened Device Tree to enumerate
>                 hardware, the device tree structure will be exposed in this
> @@ -26,3 +26,28 @@ Description:
>                 name plus address). Properties are represented as files
>                 in the directory. The contents of each file is the exact
>                 binary data from the device tree.
> +
> +What:          /sys/firmware/fdt
> +Date:          February 2015
> +KernelVersion: 3.19
> +Contact:       Frank Rowand <frank.rowand@...y.com>, devicetree@...r.kernel.org
> +Description:
> +               Exports the FDT blob that was passed to the kernel by
> +               the bootloader. This allows userland applications such
> +               as kexec to access the raw binary. This blob is also
> +               useful when debugging since it contains any changes
> +               made to the blob by the bootloader.
> +
> +               The fact that this node does not reside under
> +               /sys/firmware/device-tree is deliberate: FDT is also used
> +               on arm64 UEFI/ACPI systems to communicate just the UEFI
> +               and ACPI entry points, but the FDT is never unflattened
> +               and used to configure the system.
> +
> +               A CRC32 checksum is calculated over the entire FDT
> +               blob, and verified at late_initcall time. The sysfs
> +               entry is instantiated only if the checksum is valid,
> +               i.e., if the FDT blob has not been modified in the mean
> +               time. Otherwise, a warning is printed.
> +Users:         kexec, debugging
> +
> --
> Frank Rowand <frank.rowand@...y.com>
>