linux-kernel - Re: [rtc-linux] [PATCH] rtc: recycle id when unloading a rtc driver

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Date:	Wed, 19 Dec 2012 08:37:07 +0100
From:	Alexander Holler <holler@...oftware.de>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	Vincent Palatin <vpalatin@...omium.org>,
	rtc-linux@...glegroups.com,
	Alessandro Zummo <a.zummo@...ertech.it>,
	linux-kernel@...r.kernel.org
Subject: Re: [rtc-linux] [PATCH] rtc: recycle id when unloading a rtc driver

Am 19.12.2012 01:46, schrieb Andrew Morton:
> On Thu,  2 Aug 2012 16:53:25 -0700
> Vincent Palatin <vpalatin@...omium.org> wrote:
>
>> When calling rtc_device_unregister, we are not freeing the id used by the
>> driver.
>> So when doing a unload/load cycle for a RTC driver (e.g. rmmod rtc_cmos
>> && modprobe rtc_cmos), its id is incremented by one. As a consequence,
>> we no longer have neither an rtc0 driver nor a /proc/driver/rtc (as it
>> only exists for the first driver).
>>
>> Signed-off-by: Vincent Palatin <vpalatin@...omium.org>
>> ---
>>   drivers/rtc/class.c |    1 +
>>   1 files changed, 1 insertions(+), 0 deletions(-)
>>
>> diff --git a/drivers/rtc/class.c b/drivers/rtc/class.c
>> index dc4c274..37b1d82 100644
>> --- a/drivers/rtc/class.c
>> +++ b/drivers/rtc/class.c
>> @@ -238,6 +238,7 @@ void rtc_device_unregister(struct rtc_device *rtc)
>>   		rtc_proc_del_device(rtc);
>>   		device_unregister(&rtc->dev);
>>   		rtc->ops = NULL;
>> +		ida_simple_remove(&rtc_ida, rtc->id);
>>   		mutex_unlock(&rtc->ops_lock);
>>   		put_device(&rtc->dev);
>>   	}
>
> Now I think about it, this shouldn't have been needed?
>
> That put_device() should call rtc_device_release(), which does the
> ida_simple_remove().  Isn't that working?

It is, see the mini-thread, patch and my comment here:

https://lkml.org/lkml/2012/12/6/152

Maybe it would be better to move the ida_simple_remove from the 
rtc_device_release to rt_device_unregister as I've hinted in the above 
comment. That would make it easier to spot the ida_simple_remove().

Regards,

Alexander
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