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[217.125.87.77]) by smtp.gmail.com with ESMTPSA id h8-v6sm8736861wmb.32.2018.07.07.17.31.56 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sat, 07 Jul 2018 17:31:57 -0700 (PDT) Subject: Re: [PATCH v2] driver core: add a debugfs entry to show deferred devices To: Greg Kroah-Hartman Cc: linux-kernel@vger.kernel.org, Tomeu Vizoso , Rob Herring , Mark Brown , Andy Shevchenko , Peter Robinson , linux-arm-kernel@lists.infradead.org References: <20180627220656.19298-1-javierm@redhat.com> <20180707155921.GA26504@kroah.com> From: Javier Martinez Canillas Message-ID: Date: Sun, 8 Jul 2018 02:31:49 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0 MIME-Version: 1.0 In-Reply-To: <20180707155921.GA26504@kroah.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Greg, On 07/07/2018 05:59 PM, Greg Kroah-Hartman wrote: > On Thu, Jun 28, 2018 at 12:06:56AM +0200, Javier Martinez Canillas wrote: >> With Device Trees (DT), the dependencies of the devices are defined in the >> DT, then the drivers parse that information to lookup the needed resources >> that have as dependencies. >> >> Since drivers and devices are registered in a non-deterministic way, it is >> possible that a device that is a dependency has not been registered yet by >> the time that is looked up. >> >> In this case the driver that requires this dependency cannot probe and has >> to defer it. So the driver core adds it to a list of deferred devices that >> is iterated again every time that a new driver is probed successfully. >> >> For debugging purposes it may be useful to know what are the devices whose >> probe function was deferred. Add a debugfs entry showing that information. >> >> $ cat /sys/kernel/debug/devices_deferred >> 48070000.i2c:twl@48:bci >> musb-hdrc.0.auto >> omapdrm.0 >> >> This information could be obtained partially by enabling debugging, but it >> means that the kernel log has to be parsed and the probe deferral balanced >> with the successes. This can be error probe and has to be done in a ad-hoc >> manner by everyone who needs to debug these kind of issues. >> >> Since the information is already known by the kernel, just show it to make >> it easier to debug. >> >> Signed-off-by: Javier Martinez Canillas >> Reviewed-by: Mark Brown > > This doesn't apply to my tree anymore :( > I see, I made sure that it applied on top of linux-next. > Can you rebase and resend? > I guess you want me to rebase on top of your driver-core-next branch. I think that linux-next should pull that branch instead of the driver-core-linus one: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/Next/Trees#n29 > thanks, > > greg k-h > Best regards, -- Javier Martinez Canillas Software Engineer - Desktop Hardware Enablement Red Hat