[PATCH v2] base: driver: print dev_err_probe message on permanent probe deferral

[Johannes Zink]

This stores the probe deferral reason in the device structure.
If a probe is permanently deferred, the last reason is displayed.

Other dev_err_probe outputs are displayed as before.

Signed-off-by: Johannes Zink <j.zink at pengutronix.de>
---
v1 -> v2:
  - improved commit message
  - improved function prototypes
  - improved debug output, device name is displayed once only per
    message
  - reverted removal of MSG_DEBUG output on deferred probe
  - replaced kfree by free
  - removed unnecessary null checks before free
  - fixed several typos
  - fixed compiler warnings
  - fixed coding style issues
---
drivers/base/driver.c | 47 ++++++++++++++++++++++++++++++++++---------
 include/driver.h      |  6 ++++++
 2 files changed, 44 insertions(+), 9 deletions(-)

diff --git a/drivers/base/driver.c b/drivers/base/driver.c
index 303ca061c..02d185e01 100644
--- a/drivers/base/driver.c
+++ b/drivers/base/driver.c
@@ -283,6 +283,7 @@ void free_device_res(struct device_d *dev)
 	dev->name = NULL;
 	free(dev->unique_name);
 	dev->unique_name = NULL;
+	free(dev->deferred_probe_reason);
 }
 EXPORT_SYMBOL(free_device_res);
 
@@ -300,6 +301,12 @@ void free_device(struct device_d *dev)
 }
 EXPORT_SYMBOL(free_device);
 
+
+static char *device_get_deferred_probe_reason(const struct device_d *dev)
+{
+	return dev->deferred_probe_reason;
+}
+
 /*
  * Loop over list of deferred devices as long as at least one
  * device is successfully probed. Devices that again request
@@ -312,6 +319,7 @@ static int device_probe_deferred(void)
 	struct device_d *dev, *tmp;
 	struct driver_d *drv;
 	bool success;
+	char *reason;
 
 	do {
 		success = false;
@@ -333,9 +341,13 @@ static int device_probe_deferred(void)
 		}
 	} while (success);
 
-	list_for_each_entry(dev, &deferred, active)
-		dev_err(dev, "probe permanently deferred\n");
-
+	list_for_each_entry(dev, &deferred, active) {
+		reason = device_get_deferred_probe_reason(dev);
+		if (reason)
+			dev_err(dev, "probe permanently deferred (%s)\n", reason);
+		else
+			dev_err(dev, "probe permanently deferred\n");
+	}
 	return 0;
 }
 late_initcall(device_probe_deferred);
@@ -573,7 +585,16 @@ const void *device_get_match_data(struct device_d *dev)
 	return NULL;
 }
 
-/**
+static void device_set_deferred_probe_reason(struct device_d *dev, const struct va_format *vaf)
+{
+	char *reason;
+
+	free(dev->deferred_probe_reason);
+
+	reason = basprintf("%pV", vaf);
+	dev->deferred_probe_reason = reason;
+}
+/*
  * dev_err_probe - probe error check and log helper
  * @loglevel: log level configured in source file
  * @dev: the pointer to the struct device
@@ -584,8 +605,12 @@ const void *device_get_match_data(struct device_d *dev)
  * 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.
+ *
+ * In case of -EPROBE_DEFER it sets the device's deferred_probe_reason attribute,
+ * but does not report an error. The error is recorded and displayed later, if
+ * (and only if) the probe is permanently  deferred. For all other error codes,
+ * it just outputs the error
+ *
  * It replaces code sequence::
  *
  * 	if (err != -EPROBE_DEFER)
@@ -606,13 +631,17 @@ int dev_err_probe(const struct device_d *dev, int err, const char *fmt, ...)
 {
 	struct va_format vaf;
 	va_list args;
-
+	
 	va_start(args, fmt);
 	vaf.fmt = fmt;
 	vaf.va = &args;
 
-	dev_printf(err == -EPROBE_DEFER ? MSG_DEBUG : MSG_ERR,
-		   dev, "error %pe: %pV", ERR_PTR(err), &vaf);
+	/* deferred probe, just remember the error reason */
+	if (err == -EPROBE_DEFER)
+		device_set_deferred_probe_reason((struct device_d*)dev, &vaf);
+
+	dev_printf(err == -EPROBE_DEFER ? MSG_DEBUG : MSG_ERR, 
+		   dev, "error %pe: %pV\n", ERR_PTR(err), &vaf);
 
 	va_end(args);
 
diff --git a/include/driver.h b/include/driver.h
index b35b5f397..2dfe4719a 100644
--- a/include/driver.h
+++ b/include/driver.h
@@ -88,6 +88,12 @@ struct device_d {
 	 * when the driver should actually detect client devices
 	 */
 	int     (*detect) (struct device_d *);
+
+	/*
+	 * if a driver probe is deferred, this stores the last error
+	 */
+
+	char *deferred_probe_reason;
 };
 
 /** @brief Describes a driver present in the system */
-- 
2.30.2