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Message-ID: <10119606.2TraDKGPVy@vostro.rjw.lan> Date: Thu, 22 Oct 2015 03:06:47 +0200 From: "Rafael J. Wysocki" <rjw@...ysocki.net> To: Tomeu Vizoso <tomeu.vizoso@...labora.com> Cc: linux-kernel@...r.kernel.org, Rob Herring <robh+dt@...nel.org>, Stephen Warren <swarren@...dotorg.org>, Javier Martinez Canillas <javier@....samsung.com>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Mark Brown <broonie@...nel.org>, Thierry Reding <thierry.reding@...il.com>, Alan Stern <stern@...land.harvard.edu>, linux-arm-kernel@...ts.infradead.org, Dmitry Torokhov <dmitry.torokhov@...il.com>, devicetree@...r.kernel.org, Linus Walleij <linus.walleij@...aro.org>, linux-acpi@...r.kernel.org, Arnd Bergmann <arnd@...db.de> Subject: Re: [PATCH v6 04/22] of: add function to allow probing a device from a OF node 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 <tomeu.vizoso@...labora.com> > --- > > 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. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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