linux-kernel - [PATCH 2/3] driver core: add deferring probe reason to devices

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Message-id: <20181016072244.1216-3-a.hajda@samsung.com>
Date:   Tue, 16 Oct 2018 09:22:43 +0200
From:   Andrzej Hajda <a.hajda@...sung.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Andrzej Hajda <a.hajda@...sung.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        linux-kernel@...r.kernel.org,
        Javier Martinez Canillas <javierm@...hat.com>,
        linux-arm-kernel@...ts.infradead.org, andy.shevchenko@...il.com,
        Mark Brown <broonie@...nel.org>
Subject: [PATCH 2/3] 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 probe_err function introduced recently,
ie. if probe_err will be called with -EPROBE_DEFER instead of printk the message
will be attached to deferred device and printed when user read devices_deferred
property.

Signed-off-by: Andrzej Hajda <a.hajda@...sung.com>
---
 drivers/base/base.h |  3 +++
 drivers/base/core.c | 15 +++++++++------
 drivers/base/dd.c   | 34 +++++++++++++++++++++++++++++++++-
 3 files changed, 45 insertions(+), 7 deletions(-)

diff --git a/drivers/base/base.h b/drivers/base/base.h
index 7a419a7a6235..6f9371bfe40b 100644
--- a/drivers/base/base.h
+++ b/drivers/base/base.h
@@ -75,6 +75,7 @@ struct device_private {
 	struct klist_node knode_driver;
 	struct klist_node knode_bus;
 	struct list_head deferred_probe;
+	char *deferred_probe_msg;
 	struct device *device;
 };
 #define to_device_private_parent(obj)	\
@@ -113,6 +114,8 @@ 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 __deferred_probe_set_msg(const struct device *dev, const char *fmt,
+				     va_list args);
 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 23fabefb217a..df9895adf11b 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -3076,6 +3076,7 @@ define_dev_printk_level(_dev_info, KERN_INFO);
  *
  * This helper implements common pattern present in probe functions for error
  * checking: print message if the error is not -EPROBE_DEFER and propagate it.
+ * In case of -EPROBE_DEFER it sets defer probe reason.
  * It replaces code sequence:
  * 	if (err != -EPROBE_DEFER)
  * 		dev_err(dev, ...);
@@ -3091,15 +3092,17 @@ int probe_err(const struct device *dev, int err, const char *fmt, ...)
 	struct va_format vaf;
 	va_list args;
 
-	if (err != -EPROBE_DEFER) {
-		va_start(args, fmt);
+	va_start(args, fmt);
 
-		vaf.fmt = fmt;
-		vaf.va = &args;
+	vaf.fmt = fmt;
+	vaf.va = &args;
 
+	if (err != -EPROBE_DEFER)
 		__dev_printk(KERN_ERR, dev, &vaf);
-		va_end(args);
-	}
+	else
+		__deferred_probe_set_msg(dev, fmt, args);
+
+	va_end(args);
 
 	return err;
 }
diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index 169412ee4ae8..e2f81e538d4b 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"
@@ -132,6 +133,8 @@ 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_msg);
+		dev->p->deferred_probe_msg = NULL;
 	}
 	mutex_unlock(&deferred_probe_mutex);
 }
@@ -202,6 +205,32 @@ void device_unblock_probing(void)
 	driver_deferred_probe_trigger();
 }
 
+/*
+ * __deferred_probe_set_msg() - Set defer probe reason message for device
+ */
+void __deferred_probe_set_msg(const struct device *dev, const char *fmt,
+				     va_list args)
+{
+	const int size = 128;
+	char **p;
+	int n;
+
+	mutex_lock(&deferred_probe_mutex);
+
+	p = &dev->p->deferred_probe_msg;
+	if (!*p) {
+		*p = kmalloc(size, GFP_KERNEL);
+		if (!*p)
+			goto end;
+	}
+	n = snprintf(*p, size, "%s %s: ", dev_driver_string(dev), dev_name(dev));
+	if (n < size)
+		vsnprintf(*p + n, size - n, fmt, args);
+
+end:
+	mutex_unlock(&deferred_probe_mutex);
+}
+
 /*
  * deferred_devs_show() - Show the devices in the deferred probe pending list.
  */
@@ -212,7 +241,10 @@ 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));
+		if (curr->device->p->deferred_probe_msg)
+			seq_puts(s, curr->device->p->deferred_probe_msg);
+		else
+			seq_printf(s, "%s\n", dev_name(curr->device));
 
 	mutex_unlock(&deferred_probe_mutex);
 
-- 
2.18.0