linux-kernel - Re: [PATCH v6 02/20] liveupdate: luo

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Message-ID: <CA+CK2bAEdNE0Rs1i7GdHz8Q3DK9Npozm8sRL8Epa+o50NOMY7A@mail.gmail.com>
Date: Mon, 17 Nov 2025 23:22:54 -0500
From: Pasha Tatashin <pasha.tatashin@...een.com>
To: Mike Rapoport <rppt@...nel.org>
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Subject: Re: [PATCH v6 02/20] liveupdate: luo_core: integrate with KHO

> You can avoid that complexity if you register the device with a different
> fops, but that's technicality.
>
> Your point about treating the incoming FDT as an underlying resource that
> failed to initialize makes sense, but nevertheless userspace needs a
> reliable way to detect it and parsing dmesg is not something we should rely
> on.

I see two solutions:

1. LUO fails to retrieve the preserved data, the user gets informed by
not finding /dev/liveupdate, and studying the dmesg for what has
happened (in reality in fleets version mismatches should not be
happening, those should be detected in quals).
2. Create a zombie device to return some errno on open, and still
study dmesg to understand what really happened.

I think that 1 is better

Pasha