linux-kernel - Re: [PATCH 02/13] driver-core: defer all probes until late

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Message-ID: <2834968.DlsDAmbXkG@vostro.rjw.lan>
Date:	Thu, 18 Jun 2015 23:50:02 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Tomeu Vizoso <tomeu.vizoso@...labora.com>
Cc:	linux-arm-kernel@...ts.infradead.org,
	Alexander Holler <holler@...oftware.de>,
	Alexandre Courbot <gnurou@...il.com>,
	Andrzej Hajda <a.hajda@...sung.com>,
	Arnd Bergmann <arnd@...db.de>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Grant Likely <grant.likely@...aro.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Javier Martinez Canillas <javier.martinez@...labora.co.uk>,
	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	Kumar Gala <galak@...eaurora.org>, Len Brown <lenb@...nel.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	linux-kernel@...r.kernel.org, Lv Zheng <lv.zheng@...el.com>,
	Mark Brown <broonie@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Pawel Moll <pawel.moll@....com>,
	Robert Moore <robert.moore@...el.com>,
	Rob Herring <robh+dt@...nel.org>,
	Russell King <linux@....linux.org.uk>,
	Stephen Warren <swarren@...dotorg.org>,
	Terje Bergström <tbergstrom@...dia.com>,
	Thierry Reding <thierry.reding@...il.com>
Subject: Re: [PATCH 02/13] driver-core: defer all probes until late_initcall

On Wednesday, June 17, 2015 03:42:12 PM Tomeu Vizoso wrote:
> To decrease the chances of devices deferring their probes because of
> dependencies not having probed yet because of their drivers not having
> registered yet, delay all probing until the late initcall level.
> 
> This will allow us to avoid deferred probes completely later by probing
> dependencies on demand, or by probing them in dependency order.
> 
> Signed-off-by: Tomeu Vizoso <tomeu.vizoso@...labora.com>
> ---
>  drivers/base/dd.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/base/dd.c b/drivers/base/dd.c
> index a638bbb..18438aa 100644
> --- a/drivers/base/dd.c
> +++ b/drivers/base/dd.c
> @@ -407,6 +407,12 @@ int driver_probe_device(struct device_driver *drv, struct device *dev)
>  	if (!device_is_registered(dev))
>  		return -ENODEV;
>  
> +	/* Defer all probes until we start processing the queue */
> +	if (!driver_deferred_probe_enable) {
> +		driver_deferred_probe_add(dev);

Do I think correctly that this will effectively force everybody to use deferred
probing?

> +		return 0;
> +	}
> +
>  	pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
>  		 drv->bus->name, __func__, dev_name(dev), drv->name);
>  
> @@ -585,7 +591,7 @@ EXPORT_SYMBOL_GPL(device_attach);
>  
>  void device_initial_probe(struct device *dev)
>  {
> -	__device_attach(dev, true);
> +	__device_attach(dev, driver_deferred_probe_enable);
>  }
>  
>  static int __driver_attach(struct device *dev, void *data)
> 

-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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