diff mbox series

[v7,2/4] driver core: add deferring probe reason to devices_deferred property

Message ID 20200629112242.18380-3-a.hajda@samsung.com (mailing list archive)
State New, archived
Headers show
Series [v7,1/4] driver core: add device probe log helper | expand

Commit Message

Andrzej Hajda June 29, 2020, 11:22 a.m. UTC 
/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 deferred device and printed when user read devices_deferred
property.

Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Reviewed-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Rafael J. Wysocki <rafael@kernel.org>
---
 drivers/base/base.h |  3 +++
 drivers/base/core.c |  8 ++++++--
 drivers/base/dd.c   | 23 ++++++++++++++++++++++-
 3 files changed, 31 insertions(+), 3 deletions(-)

Comments

Andy Shevchenko June 29, 2020, 4:36 p.m. UTC | #1 
On Mon, Jun 29, 2020 at 2:22 PM Andrzej Hajda <a.hajda@samsung.com> wrote:
>
> /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 deferred device and printed when user read devices_deferred

to a deferred

reads

> property.

...

> @@ -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) {

Why not positive conditional? (Okay, I'm fine with either in this case)

>                 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);
> +       }

To reduce churn, you may move {} addition to the first patch.

...

>         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");

Hmm... "\t" will be dangling in the latter case.
Andrzej Hajda June 30, 2020, 8:32 a.m. UTC | #2 
On 29.06.2020 18:36, Andy Shevchenko wrote:
> On Mon, Jun 29, 2020 at 2:22 PM Andrzej Hajda <a.hajda@samsung.com> wrote:
>> /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 deferred device and printed when user read devices_deferred
> to a deferred
>
> reads
OK, thx.
>
>> property.
> ...
>
>> @@ -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) {
> Why not positive conditional? (Okay, I'm fine with either in this case)


I put more natural branch 1st.


>
>>                  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);
>> +       }
> To reduce churn, you may move {} addition to the first patch.


But then I need to explain why it is there :)


>
> ...
>
>>          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");
> Hmm... "\t" will be dangling in the latter case


Hmm, I followed your advice [1] :)

[1]: 
https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1787370.html


Regards

Andrzej


>
Andy Shevchenko June 30, 2020, 10 a.m. UTC | #3 
On Tue, Jun 30, 2020 at 11:32 AM Andrzej Hajda <a.hajda@samsung.com> wrote:
> On 29.06.2020 18:36, Andy Shevchenko wrote:
> > On Mon, Jun 29, 2020 at 2:22 PM Andrzej Hajda <a.hajda@samsung.com> wrote:
> >> /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 deferred device and printed when user read devices_deferred
> > to a deferred
> >
> > reads
> OK, thx.
> >
> >> property.

...

> >>          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");
> > Hmm... "\t" will be dangling in the latter case
>
>
> Hmm, I followed your advice [1] :)
>
> [1]:
> https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1787370.html

Ah, indeed :-)
Okay, as I  said I'm fine with the code. Since it's debugfs, we are fine.
diff mbox series

Patch

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 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);