From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754915AbbJVAh6 (ORCPT ); Wed, 21 Oct 2015 20:37:58 -0400 Received: from v094114.home.net.pl ([79.96.170.134]:49449 "HELO v094114.home.net.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1750756AbbJVAh4 (ORCPT ); Wed, 21 Oct 2015 20:37:56 -0400 From: "Rafael J. Wysocki" To: Tomeu Vizoso Cc: linux-kernel@vger.kernel.org, Rob Herring , Stephen Warren , Javier Martinez Canillas , Greg Kroah-Hartman , Mark Brown , Thierry Reding , Alan Stern , linux-arm-kernel@lists.infradead.org, Dmitry Torokhov , devicetree@vger.kernel.org, Linus Walleij , linux-acpi@vger.kernel.org, Arnd Bergmann Subject: Re: [PATCH v6 04/22] of: add function to allow probing a device from a OF node Date: Thu, 22 Oct 2015 03:06:47 +0200 Message-ID: <10119606.2TraDKGPVy@vostro.rjw.lan> User-Agent: KMail/4.11.5 (Linux/4.1.0-rc5+; KDE/4.11.5; x86_64; ; ) In-Reply-To: <1442844182-27787-5-git-send-email-tomeu.vizoso@collabora.com> References: <1442844182-27787-1-git-send-email-tomeu.vizoso@collabora.com> <1442844182-27787-5-git-send-email-tomeu.vizoso@collabora.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="utf-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Monday, September 21, 2015 04:02:44 PM Tomeu Vizoso wrote: > Walks the OF tree up and finds the closest ancestor that has a struct > device associated with it, probing it if isn't bound to a driver yet. > > The above should ensure that the dependency represented by the passed OF > node is available, because probing a device should cause its descendants > to be probed as well (when they get registered). > > Subsystems can use this when looking up resources for drivers, to reduce > the chances of deferred probes because of the probing order of devices. > > Signed-off-by: Tomeu Vizoso > --- > > Changes in v5: > - Move the assignment to device_node->device for AMBA devices to another > commit. > - Hold a reference to the struct device while it's in use in > of_device_probe(). > > Changes in v4: > - Rename of_platform_probe to of_device_probe > - Use device_node.device instead of device_node.platform_dev > > Changes in v3: > - Set and use device_node.platform_dev instead of reversing the logic to > find the platform device that encloses a device node. > - Drop the fwnode API to probe firmware nodes and add OF-only API for > now. I think this same scheme could be used for machines with ACPI, > but I haven't been able to find one that had to defer its probes because > of the device probe order. > > drivers/of/device.c | 61 +++++++++++++++++++++++++++++++++++++++++++++++ > include/linux/of_device.h | 3 +++ > 2 files changed, 64 insertions(+) > > diff --git a/drivers/of/device.c b/drivers/of/device.c > index 8b91ea241b10..836be71fc90e 100644 > --- a/drivers/of/device.c > +++ b/drivers/of/device.c > @@ -286,3 +286,64 @@ int of_device_uevent_modalias(struct device *dev, struct kobj_uevent_env *env) > > return 0; > } > + > +/** > + * of_device_probe() - Probe device associated with OF node > + * @np: node to probe > + * > + * Probe the device associated with the passed device node. > + */ > +void of_device_probe(struct device_node *np) Same question as from Greg: How does a subsystem know whether or not to use this function? > +{ > + struct device_node *target; > + struct device *dev = NULL; > + > + if (!of_root || !of_node_check_flag(of_root, OF_POPULATED_BUS)) > + return; > + > + if (!np) > + return; > + > + of_node_get(np); > + > + /* Find the closest ancestor that has a device associated */ > + for (target = np; > + !of_node_is_root(target); > + target = of_get_next_parent(target)) > + if (get_device(target->device)) { > + dev = target->device; > + break; > + } > + > + of_node_put(target); > + > + if (!dev) { > + pr_warn("Couldn't find a device for node '%s'\n", > + of_node_full_name(np)); > + return; > + } > + > + /* > + * Device is bound or is being probed right now. If we have bad luck > + * and the dependency isn't ready when it's needed, deferred probe > + * will save us. > + */ > + if (dev->driver) > + goto out; > + > + /* > + * Probing a device should cause its descendants to be probed as > + * well, which includes the passed device node. > + */ > + if (device_attach(dev) != 1) > + /* > + * This cannot be a warning for now because clock nodes have a > + * compatible string but the clock framework doesn't follow > + * the device/driver model yet. > + */ > + dev_dbg(dev, "Probe failed for %s\n", of_node_full_name(np)); > + > +out: > + put_device(dev); > +} > +EXPORT_SYMBOL_GPL(of_device_probe); > diff --git a/include/linux/of_device.h b/include/linux/of_device.h > index cc7dd687a89d..da8d489e73ad 100644 > --- a/include/linux/of_device.h > +++ b/include/linux/of_device.h > @@ -40,6 +40,7 @@ extern ssize_t of_device_get_modalias(struct device *dev, > > extern void of_device_uevent(struct device *dev, struct kobj_uevent_env *env); > extern int of_device_uevent_modalias(struct device *dev, struct kobj_uevent_env *env); > +extern void of_device_probe(struct device_node *np); > > static inline void of_device_node_put(struct device *dev) > { > @@ -84,6 +85,8 @@ static inline int of_device_uevent_modalias(struct device *dev, > return -ENODEV; > } > > +static inline void of_device_probe(struct device_node *np) { } > + > static inline void of_device_node_put(struct device *dev) { } > > static inline const struct of_device_id *__of_match_device( > -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center.