linux-kernel - [PATCH v2 1/2] driver core: clear deferred probe reason on probe retry

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Date:   Fri, 19 Mar 2021 12:04:57 +0100
From:   Ahmad Fatoum <a.fatoum@...gutronix.de>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Javier Martinez Canillas <javierm@...hat.com>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Mark Brown <broonie@...nel.org>
Cc:     kernel@...gutronix.de, andy.shevchenko@...il.com,
        stable@...nel.org, Ahmad Fatoum <a.fatoum@...gutronix.de>,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 1/2] driver core: clear deferred probe reason on probe retry

When retrying a deferred probe, any old defer reason string should be
discarded. Otherwise, if the probe is deferred again at a different spot,
but without setting a message, the now incorrect probe reason will remain.

This was observed with the i.MX I2C driver, which ultimately failed
to probe due to lack of the GPIO driver. The probe defer for GPIO
doesn't record a message, but a previous probe defer to clock_get did.
This had the effect that /sys/kernel/debug/devices_deferred listed
a misleading probe deferral reason.

Cc: stable@...nel.org
Fixes: d090b70ede02 ("driver core: add deferring probe reason to devices_deferred property")
Reviewed-by: Andy Shevchenko <andy.shevchenko@...il.com>
Signed-off-by: Ahmad Fatoum <a.fatoum@...gutronix.de>
---
v1 -> v2:
 - reworded commit message (Andy)
 - collected Andy's Reviewed-by
---
 drivers/base/dd.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index 9179825ff646..e2cf3b29123e 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -97,6 +97,9 @@ static void deferred_probe_work_func(struct work_struct *work)
 
 		get_device(dev);
 
+		kfree(dev->p->deferred_probe_reason);
+		dev->p->deferred_probe_reason = NULL;
+
 		/*
 		 * Drop the mutex while probing each device; the probe path may
 		 * manipulate the deferred list
-- 
2.29.2