linux-kernel - Re: [PATCH v2 1/8] driver core: make deferring probe after init optional

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Message-ID: <1765be22-4bd7-c870-926c-2956e46df1d9@gmail.com>
Date:   Mon, 28 May 2018 22:12:14 -0700
From:   Frank Rowand <frowand.list@...il.com>
To:     Mark Brown <broonie@...nel.org>, Rob Herring <robh@...nel.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Alexander Graf <agraf@...e.de>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Kevin Hilman <khilman@...nel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Joerg Roedel <joro@...tes.org>,
        Robin Murphy <robin.murphy@....com>,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        boot-architecture@...ts.linaro.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 1/8] driver core: make deferring probe after init
 optional

On 05/24/18 11:18, Mark Brown wrote:
> On Thu, May 24, 2018 at 12:50:17PM -0500, Rob Herring wrote:
> 
>> Subsystems or drivers may opt-in to this behavior by calling
>> driver_deferred_probe_check_init_done() instead of just returning
>> -EPROBE_DEFER. They may use additional information from DT or kernel's
>> config to decide whether to continue to defer probe or not.
> 
> Should userspace have some involvement in this decision?  It knows if
> it's got any intention of loading modules for example.  Kernel config
> checks might be good enough, though it's going to be a pain to work out
> if the relevant driver is built as a module for example.
> 

A parallel issue is that loading an overlay could provide the resource
that will allow the deferred probe to complete.  (That is, once we
finish implementing the run time overlays feature.)

-Frank