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

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Date:	Thu, 22 Oct 2015 01:39:42 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Geert Uytterhoeven <geert@...ux-m68k.org>
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>,
	Kishon Vijay Abraham I <kishon@...com>,
	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,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	dri-devel <dri-devel@...ts.freedesktop.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	"linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Linux PWM List <linux-pwm@...r.kernel.org>,
	Linux USB List <linux-usb@...r.kernel.org>,
	"linux-fbdev@...r.kernel.org" <linux-fbdev@...r.kernel.org>
Subject: Re: [GIT PULL] On-demand device probing

On Wednesday, October 21, 2015 10:55:14 AM Geert Uytterhoeven wrote:
> 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?

Currently, there's no native way to represent those dependencies in ACPI.

Thanks,
Rafael

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