linux-kernel - Re: [GIT PULL] On-demand device probing

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Message-ID: <CAMuHMdWoSdoT1p0e+Bc9ucrykxO7ESLKYHRzackpVjQAs_XaDg@mail.gmail.com>
Date:	Wed, 21 Oct 2015 10:55:14 +0200
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	Rob Herring <robh@...nel.org>,
	David Woodhouse <dwmw2@...radead.org>,
	Mark Brown <broonie@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Tomeu Vizoso <tomeu.vizoso@...labora.com>,
	Russell King <linux@....linux.org.uk>,
	Michael Turquette <mturquette@...libre.com>,
	Stephen Boyd <sboyd@...eaurora.org>,
	Vinod Koul <vinod.koul@...el.com>,
	Dan Williams <dan.j.williams@...el.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Alexandre Courbot <gnurou@...il.com>,
	Thierry Reding <thierry.reding@...il.com>,
	David Airlie <airlied@...ux.ie>,
	Terje Bergström <tbergstrom@...dia.com>,
	Stephen Warren <swarren@...dotorg.org>,
	Wolfram Sang <wsa@...-dreams.de>,
	Frank Rowand <frowand.list@...il.com>,
	Grant Likely <grant.likely@...aro.org>,
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	Sebastian Reichel <sre@...nel.org>,
	Dmitry Eremin-Solenikov <dbaryshkov@...il.com>,
	Liam Girdwood <lgirdwood@...il.com>,
	Felipe Balbi <balbi@...com>, Jingoo Han <jingoohan1@...il.com>,
	Lee Jones <lee.jones@...aro.org>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	Tomi Valkeinen <tomi.valkeinen@...com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-clk <linux-clk@...r.kernel.org>, dmaengine@...r.kernel.org,
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	dri-devel <dri-devel@...ts.freedesktop.org>,
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	"linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
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Subject: Re: [GIT PULL] On-demand device probing

Hi Rafael,

On Wed, Oct 21, 2015 at 1:34 AM, Rafael J. Wysocki <rjw@...ysocki.net> wrote:
> On Tuesday, October 20, 2015 09:15:01 AM Rob Herring wrote:
>> On Tue, Oct 20, 2015 at 2:56 AM, Rafael J. Wysocki <rjw@...ysocki.net> wrote:
>> > ACPI uses platform devices too.  In fact, ACPI device objects are enumerated as
>> > platform devices by default now.
>>
>> Okay, I should have grepped for that:
>> drivers/base/platform.c:                ACPI_COMPANION_SET(&pdev->dev, NULL);
>> drivers/base/platform.c:        len = acpi_device_modalias(dev, buf,
>> PAGE_SIZE -1);
>> drivers/base/platform.c:        rc = acpi_device_uevent_modalias(dev, env);
>> drivers/base/platform.c:        /* Then try ACPI style match */
>> drivers/base/platform.c:        if (acpi_driver_match_device(dev, drv))
>>
>> These are all cases which have DT version as well, so we're not really
>> all that different here. There's a few more for DT, but that probably
>> means you have just not hit the problems we have yet. For example,
>> what happens if you have an interrupt line in which the controller is
>> probed after the device connected to the interrupt line? That required
>> resolving irqs in platform_get_irq rather than using static resources
>> to support deferred probe.
>
> We don't have this particular problem, because the IRQ controllers are
> enumerated in a special way.

What does "in a special way" mean? Can you please be more specific?

Can you have interrupt controllers that depend on clocks, pin controllers,
and PM domains?

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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