RE: [PATCH v8 2/5] driver core: add deferring probe reason to devices_deferred property

[Ruhl, Michael J]

>-----Original Message-----
>From: dri-devel <dri-devel-bounces@xxxxxxxxxxxxxxxxxxxxx> On Behalf Of
>Andrzej Hajda
>Sent: Friday, July 10, 2020 11:30 AM
>To: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
>Cc: Jernej Skrabec <jernej.skrabec@xxxxxxxx>; Rafael J. Wysocki
><rafael@xxxxxxxxxx>; Jonas Karlman <jonas@xxxxxxxxx>; Bartlomiej
>Zolnierkiewicz <b.zolnierkie@xxxxxxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx;
>open list:DRM DRIVERS <dri-devel@xxxxxxxxxxxxxxxxxxxxx>; Russell King - ARM
>Linux <linux@xxxxxxxxxxxxxxx>; Neil Armstrong <narmstrong@xxxxxxxxxxxx>;
>Andrzej Hajda <a.hajda@xxxxxxxxxxx>; andy.shevchenko@xxxxxxxxx; Mark
>Brown <broonie@xxxxxxxxxx>; Laurent Pinchart
><Laurent.pinchart@xxxxxxxxxxxxxxxx>; linux-arm-
>kernel@xxxxxxxxxxxxxxxxxxx; Marek Szyprowski
><m.szyprowski@xxxxxxxxxxx>
>Subject: [PATCH v8 2/5] driver core: add deferring probe reason to
>devices_deferred property
>
>/sys/kernel/debug/devices_deferred property contains list of deferred
>devices.
>This list does not contain reason why the driver deferred probe, the patch
>improves it.
>The natural place to set the reason is dev_err_probe function introduced
>recently, ie. if dev_err_probe will be called with -EPROBE_DEFER instead of
>printk the message will be attached to a deferred device and printed when
>user
>reads devices_deferred property.
>
>Signed-off-by: Andrzej Hajda <a.hajda@xxxxxxxxxxx>
>Reviewed-by: Mark Brown <broonie@xxxxxxxxxx>
>Reviewed-by: Javier Martinez Canillas <javierm@xxxxxxxxxx>
>Reviewed-by: Andy Shevchenko <andy.shevchenko@xxxxxxxxx>
>Reviewed-by: Rafael J. Wysocki <rafael@xxxxxxxxxx>
>---
>v8:
>- improved commit message
>---
> drivers/base/base.h |  3 +++
> drivers/base/core.c |  8 ++++++--
> drivers/base/dd.c   | 23 ++++++++++++++++++++++-
> 3 files changed, 31 insertions(+), 3 deletions(-)
>
>diff --git a/drivers/base/base.h b/drivers/base/base.h
>index 95c22c0f9036..6954fccab3d7 100644
>--- a/drivers/base/base.h
>+++ b/drivers/base/base.h
>@@ -93,6 +93,7 @@ struct device_private {
> 	struct klist_node knode_class;
> 	struct list_head deferred_probe;
> 	struct device_driver *async_driver;
>+	char *deferred_probe_reason;
> 	struct device *device;
> 	u8 dead:1;
> };
>@@ -134,6 +135,8 @@ extern void device_release_driver_internal(struct
>device *dev,
> extern void driver_detach(struct device_driver *drv);
> extern int driver_probe_device(struct device_driver *drv, struct device
>*dev);
> extern void driver_deferred_probe_del(struct device *dev);
>+extern void device_set_deferred_probe_reson(const struct device *dev,
>+					    struct va_format *vaf);
> static inline int driver_match_device(struct device_driver *drv,
> 				      struct device *dev)
> {
>diff --git a/drivers/base/core.c b/drivers/base/core.c
>index 3a827c82933f..fee047f03681 100644
>--- a/drivers/base/core.c
>+++ b/drivers/base/core.c
>@@ -3963,6 +3963,8 @@ define_dev_printk_level(_dev_info, KERN_INFO);
>  * This helper implements common pattern present in probe functions for
>error
>  * checking: print debug or error message depending if the error value is
>  * -EPROBE_DEFER and propagate error upwards.
>+ * In case of -EPROBE_DEFER it sets also defer probe reason, which can be
>+ * checked later by reading devices_deferred debugfs attribute.
>  * It replaces code sequence:
>  * 	if (err != -EPROBE_DEFER)
>  * 		dev_err(dev, ...);
>@@ -3984,10 +3986,12 @@ int dev_err_probe(const struct device *dev, int
>err, const char *fmt, ...)
> 	vaf.fmt = fmt;
> 	vaf.va = &args;
>
>-	if (err != -EPROBE_DEFER)
>+	if (err != -EPROBE_DEFER) {
> 		dev_err(dev, "error %d: %pV", err, &vaf);
>-	else
>+	} else {
>+		device_set_deferred_probe_reson(dev, &vaf);
> 		dev_dbg(dev, "error %d: %pV", err, &vaf);
>+	}
>
> 	va_end(args);
>
>diff --git a/drivers/base/dd.c b/drivers/base/dd.c
>index 9a1d940342ac..dd5683b61f74 100644
>--- a/drivers/base/dd.c
>+++ b/drivers/base/dd.c
>@@ -27,6 +27,7 @@
> #include <linux/async.h>
> #include <linux/pm_runtime.h>
> #include <linux/pinctrl/devinfo.h>
>+#include <linux/slab.h>
>
> #include "base.h"
> #include "power/power.h"
>@@ -136,6 +137,8 @@ void driver_deferred_probe_del(struct device *dev)
> 	if (!list_empty(&dev->p->deferred_probe)) {
> 		dev_dbg(dev, "Removed from deferred list\n");
> 		list_del_init(&dev->p->deferred_probe);
>+		kfree(dev->p->deferred_probe_reason);
>+		dev->p->deferred_probe_reason = NULL;
> 	}
> 	mutex_unlock(&deferred_probe_mutex);
> }
>@@ -211,6 +214,23 @@ void device_unblock_probing(void)
> 	driver_deferred_probe_trigger();
> }
>
>+/**
>+ * device_set_deferred_probe_reson() - Set defer probe reason message
>for device
>+ * @dev: the pointer to the struct device
>+ * @vaf: the pointer to va_format structure with message
>+ */
>+void device_set_deferred_probe_reson(const struct device *dev, struct

Is 'reson'  supposed to be 'reason'?

Same spelling on the above kernel-doc, but the comment says "reason".

mike

>va_format *vaf)
>+{
>+	const char *drv = dev_driver_string(dev);
>+
>+	mutex_lock(&deferred_probe_mutex);
>+
>+	kfree(dev->p->deferred_probe_reason);
>+	dev->p->deferred_probe_reason = kasprintf(GFP_KERNEL, "%s:
>%pV", drv, vaf);
>+
>+	mutex_unlock(&deferred_probe_mutex);
>+}
>+
> /*
>  * deferred_devs_show() - Show the devices in the deferred probe pending
>list.
>  */
>@@ -221,7 +241,8 @@ static int deferred_devs_show(struct seq_file *s, void
>*data)
> 	mutex_lock(&deferred_probe_mutex);
>
> 	list_for_each_entry(curr, &deferred_probe_pending_list,
>deferred_probe)
>-		seq_printf(s, "%s\n", dev_name(curr->device));
>+		seq_printf(s, "%s\t%s", dev_name(curr->device),
>+			   curr->device->p->deferred_probe_reason ?: "\n");
>
> 	mutex_unlock(&deferred_probe_mutex);
>
>--
>2.17.1
>
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