linux-kernel - [PATCHv2 1/2] hwmon: core: add thermal sensors only if dev->of

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Message-ID: <20190530025605.3698-2-eduval@amazon.com>
Date:   Wed, 29 May 2019 19:56:04 -0700
From:   Eduardo Valentin <eduval@...zon.com>
To:     Guenter Roeck <linux@...ck-us.net>
CC:     Eduardo Valentin <eduval@...zon.com>,
        Jean Delvare <jdelvare@...e.com>,
        <linux-hwmon@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCHv2 1/2] hwmon: core: add thermal sensors only if dev->of_node is present

Drivers may register to hwmon and request for also registering
with the thermal subsystem (HWMON_C_REGISTER_TZ). However,
some of these driver, e.g. marvell phy, may be probed from
Device Tree or being dynamically allocated, and in the later
case, it will not have a dev->of_node entry.

Registering with hwmon without the dev->of_node may result in
different outcomes depending on the device tree, which may
be a bit misleading. If the device tree blob has no 'thermal-zones'
node, the *hwmon_device_register*() family functions are going
to gracefully succeed, because of-thermal,
*thermal_zone_of_sensor_register() return -ENODEV in this case,
and the hwmon error path handles this error code as success to
cover for the case where CONFIG_THERMAL_OF is not set.
However, if the device tree blob has the 'thermal-zones'
entry, the *hwmon_device_register*() will always fail on callers
with no dev->of_node, propagating -EINVAL.

If dev->of_node is not present, calling of-thermal does not
make sense. For this reason, this patch checks first if the
device has a of_node before going over the process of registering
with the thermal subsystem of-thermal interface. And in this case,
when a caller of *hwmon_device_register*() with HWMON_C_REGISTER_TZ
and no dev->of_node will still register with hwmon, but not with
the thermal subsystem. If all the hwmon part bits are in place,
the registration will succeed.

Cc: Jean Delvare <jdelvare@...e.com>
Cc: Guenter Roeck <linux@...ck-us.net>
Cc: linux-hwmon@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
Signed-off-by: Eduardo Valentin <eduval@...zon.com>
---
V1->V2: no change

 drivers/hwmon/hwmon.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/hwmon/hwmon.c b/drivers/hwmon/hwmon.c
index e694c46ff039..429784edd5ff 100644
--- a/drivers/hwmon/hwmon.c
+++ b/drivers/hwmon/hwmon.c
@@ -636,7 +636,7 @@ __hwmon_device_register(struct device *dev, const char *name, void *drvdata,
 	if (err)
 		goto free_hwmon;

-	if (dev && chip && chip->ops->read &&
+	if (dev && dev->of_node && chip && chip->ops->read &&
 	    chip->info[0]->type == hwmon_chip &&
 	    (chip->info[0]->config[0] & HWMON_C_REGISTER_TZ)) {
 		const struct hwmon_channel_info **info = chip->info;
-- 
2.21.0