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From:   valdis.kletnieks@vt.edu
To:     frowand.list@gmail.com
Cc:     Rob Herring <robh+dt@kernel.org>, pantelis.antoniou@konsulko.com,
        Pantelis Antoniou <panto@antoniou-consulting.com>,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
        geert@linux-m68k.org, Alan Tull <atull@kernel.org>
Subject: Re: [PATCH v2] of: overlay: user space synchronization
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Date:   Mon, 15 Oct 2018 20:35:58 -0400
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On Mon, 15 Oct 2018 17:27:01 -0700, frowand.list@gmail.com said:
> From: Frank Rowand <frank.rowand@sony.com>
>
> When an overlay is applied or removed, the live devicetree visible in
> /proc/device-tree/, aka /sys/firmware/devicetree/base/, reflects the
> changes.  There is no method for user space to determine whether the
> live devicetree was modified by overlay actions.
>
> Provide a sysfs file, /sys/firmware/devicetree/tree_version,  to allow
> user space to determine if the live devicetree has remained unchanged
> while a series of one or more accesses of /proc/device-tree/ occur.
>
> The use of both dynamic devicetree modifications and overlay apply and
> removal are not supported during the same boot cycle.  Thus non-overlay
> dynamic modifications are not reflected in the value of tree_version.

Is there an easy way from userspace to detect "yes/no dynamic modifications
have been done since boot"?

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