Am 19.06.2019 um 20:53 schrieb Guenter Roeck:
On Wed, Jun 19, 2019 at 12:00:37PM +0200, Christian Schneider wrote:
Ok, seems that moving that block, where fan_alarm_init is called down, isn't
a problem on master.
I need to use 4.9, cause we have an embedded device that needs patches, and
they are only available for older kernels.
In 4.9, fan_alarm_init() does fan_data->alarm = alarm;
When fan_alarm_init() is called after
devm_hwmon_device_register_with_groups(), then fan_data->alarm is not yet
set, so the sysfs attribute is not created.
when I move the fan_data->alarm = alarm; out of fan_alarm_init() before
devm_hwmon_device_register_with_groups() and the fan_alarm_init() after,
then it works, and doesn't have a race condition.
On master, populating fan_data->alarm_gpio is done in
gpio_fan_get_of_data(fan_data); as far as I understand, so moving the
fan_alarm_init() block further down shouldn't be a problem.
I don't know, how I can test this with master kernel. Unfortunately, the
device, I'm using doesn't have a recent kernel. And on my normal (desktop)
pc, I don't have a gpio fan.
How should I proceed now?
Essentially, we'll need two patches: One to move fan_alarm_init() after
devm_hwmon_device_register_with_groups(), and then the notification patch.
For the backport to v4.9, the first patch will have to be slightly modified:
The first part will a simple
fan_data->alarm = pdata->alarm;
at the location where fan_alarm_init() is called now, the second part is to move
the call to fan_alarm_init() after devm_hwmon_device_register_with_groups().
It is ok to test the result with your 4.9 based kernel; we'll just have to be
careful when reviewing the mainline patch.
Thanks,
Guenter
Ok,
it seems like it is working as expected now on my 4.9 kernel. No
race-condition and notification is received.
I will adopt the changes to mainline kernel, but not sure if I can make
it today. Might be Monday, till I have the patch.
BR, Christian
BR, Christian
Am 19.06.2019 um 09:47 schrieb Christian Schneider:
Hi,
unfrotunately I found a problem with my patch. It didn't appear on the
devices, where I tested, only when distributing the patch to more devices,
it occurs sometimes.
There is a possible race condition. In gpio_fan_probe, the IRQ handler for
the fan alarm is registered before the hwmon_dev is initialised.
So it is possible, that the handler executes, while fandata->hwmon_dev is
still unitialised and the handler runs in an invalid pointer dereference.
The obvious fix, moving the
/* Configure alarm GPIO if available. */
if (fan_data->alarm_gpio) {
err = fan_alarm_init(fan_data);
if (err)
return err;
}
block after
/* Make this driver part of hwmon class. */
fan_data->hwmon_dev =
devm_hwmon_device_register_with_groups(dev,
"gpio_fan", fan_data,
gpio_fan_groups);
doesn't work. Sysfs doesn't have a fan1_alarm attribute anymore then.
It is not yet clear to me, why creation of the attribute fails in this
case. I need to investigate further.
In the meanwhile, please revert my patch.
I'm sorry for the disturbance I created....
BR, Christian
Am 17.06.2019 um 18:04 schrieb Guenter Roeck:
On Mon, Jun 17, 2019 at 11:33:43AM +0200, cschneider@xxxxxxxxxxxxx wrote:
From: Christian Schneider <christian@xxxxxxxx>
sysfs_notify and kobject_uevent are passed the wrong kobject.
that why notifications can't be received and uevents have the wrong
path.
this patch fixes this.
Signed-off-by: Christian Schneider <cschneider@xxxxxxxxxxxxx>
Applied.
In the future, please version your patches, add a change log,
and reflect the subsystem and driver in the subject line.
Thanks,
Guenter
---
drivers/hwmon/gpio-fan.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/hwmon/gpio-fan.c b/drivers/hwmon/gpio-fan.c
index 84753680a4e8..76377791ff0e 100644
--- a/drivers/hwmon/gpio-fan.c
+++ b/drivers/hwmon/gpio-fan.c
@@ -54,8 +54,8 @@ static void fan_alarm_notify(struct work_struct *ws)
struct gpio_fan_data *fan_data =
container_of(ws, struct gpio_fan_data, alarm_work);
- sysfs_notify(&fan_data->dev->kobj, NULL, "fan1_alarm");
- kobject_uevent(&fan_data->dev->kobj, KOBJ_CHANGE);
+ sysfs_notify(&fan_data->hwmon_dev->kobj, NULL, "fan1_alarm");
+ kobject_uevent(&fan_data->hwmon_dev->kobj, KOBJ_CHANGE);
}
static irqreturn_t fan_alarm_irq_handler(int irq, void *dev_id)
