From: Alexander Holler <holler@ahsoftware.de>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org, rtc-linux@googlegroups.com,
Alessandro Zummo <a.zummo@towertech.it>,
Lars-Peter Clausen <lars@metafoo.de>,
Jonathan Cameron <jic23@cam.ac.uk>, Jiri Kosina <jkosina@suse.cz>
Subject: Re: [PATCH 3/3] rtc: rtc-hid-sensor-time; add option hctosys to set time at boot
Date: Tue, 23 Apr 2013 12:08:12 +0200 [thread overview]
Message-ID: <51765D8C.1010008@ahsoftware.de> (raw)
In-Reply-To: <51764B8E.9090402@ahsoftware.de>
Am 23.04.2013 10:51, schrieb Alexander Holler:
> Am 23.04.2013 01:38, schrieb Andrew Morton:
>> On Fri, 19 Apr 2013 17:14:12 +0200 Alexander Holler
>> <holler@ahsoftware.de> wrote:
>>
>>> drivers/rtc/hctosys (CONFIG_RTC_HCTOSYS) doesn't work for
>>> rtc-hid-sensor-time because it will be called in late_init, and thus
>>> before
>>> rtc-hid-sensor-time gets loaded.
>>
>> Isn't that true of all RTC drivers which are built as modules? There's
>> nothing special about hid-sensor-time here?
>>
>> I assume the standard answer here is "your RTC driver should be built
>> into vmlinux". If we wish to make things work for modular RTC drivers
>> then we should find a solution which addresses *all* RTC drivers?
>
> No. I having rtc-hid-sensor-time, hid-sensor-hub (and USB) statically
> linked in doesn't help. Here is what happens here with such an
> configuration:
>
> --
> [ 7.638970] drivers/rtc/hctosys.c: unable to open rtc device (rtc0)
> [ 7.645639] Waiting 180sec before mounting root device...
> [ 16.598759] HID-SENSOR-2000a0 HID-SENSOR-2000a0.0: rtc core:
> registered hid-sensor-time as rtc0
> [ 16.608712] HID-SENSOR-2000a0 HID-SENSOR-2000a0.0: hctosys: setting
> system clock to 2013-04-19 16:45:06 UTC (1366389906)
> --
>
> I havent't looked in detail at why rtc-hid-sensor-time gets loaded that
> late, but I assume it's because the USB stack (and/or the device or the
> communication inbetween) needs some time (and I assume that's why
> rootwait and rootdelay got invented too).
>
>>
>>> To set the time through rtc-hid-sensor-time
>>> at startup, the module now checks by default if the system time is
>>> before
>>> 1970-01-02 and sets the system time (once) if this is the case.
>>>
>>> To disable this behaviour, set the module option hctosys to zero,
>>> e.g. by
>>> using rtc-hid-sensor-time.hctosys=0 at the kernel command line if the
>>> driver is statically linked into the kernel.
>>
>> Is a bit hacky, no?
>
> I didn't have any other idea to prevent an USB (or any other
> hot-pluggable HID) device to change the time while still beeing able (by
> default) to set the time by such an device at boot. But I'm open to
> suggestions. (E.g. one of the scenarios I want to prevent is, that a
> computer gets it's time by NTP and someone is able to change the time
> later on by simply plugging in some HID device.)
>
To add something more: I use the system time as a bool
"time_was_set_once" and have choosen one day just in case something
needs really long to boot (e.g. because of some lengthy fsck or whatever
else).
A solution to both problems might be to change the logic for hctosys
completly to read the time when the first RTC device appears (or when
the device mentioned in CONFIG_RTC_HCTOSYS_DEVICE appears). But that
would require a change to hctosys or the RTC subsystem, which would
involve more patches and discussion. As rtc-hid-sensor-time currently
seems to be the only RTC with the above problems, I've gone the easy
route and only modified this driver.
Regards,
Alexander
next prev parent reply other threads:[~2013-04-23 10:08 UTC|newest]
Thread overview: 77+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-04-19 15:14 [PATCH 0/3] rtc: rtc-hid-sensor-time Alexander Holler
2013-04-19 15:14 ` [PATCH 1/3 RESEND] rtc: rtc-hid-sensor-time: allow full years (16bit) in HID reports Alexander Holler
2013-04-19 15:14 ` [PATCH 2/3] rtc: rtc-hid-sensor-time: allow 16 and 32 bit values for all attributes Alexander Holler
2013-04-19 15:14 ` [PATCH 3/3] rtc: rtc-hid-sensor-time; add option hctosys to set time at boot Alexander Holler
2013-04-22 23:38 ` Andrew Morton
2013-04-23 8:51 ` Alexander Holler
2013-04-23 10:08 ` Alexander Holler [this message]
2013-04-23 10:13 ` Alexander Holler
2013-04-23 10:17 ` Alexander Holler
2013-04-23 15:47 ` Alexander Holler
2013-04-24 21:14 ` Andrew Morton
2013-04-25 6:55 ` Alexander Holler
2013-05-05 11:21 ` [PATCH 0/4] rtc: rtc-hid-sensor-time: some changes Alexander Holler
2013-05-05 11:21 ` [PATCH 1/4] rtc: rtc-hid-sensor-time: allow full years (16bit) in HID reports Alexander Holler
2013-05-05 11:21 ` [PATCH 2/4] rtc: rtc-hid-sensor-time: allow 16 and 32 bit values for all attributes Alexander Holler
2013-05-05 11:21 ` [PATCH 3/4] rtc: rtc-hid-sensor-time: add option hctosys to set time at boot Alexander Holler
2013-05-21 21:42 ` Andrew Morton
2013-05-21 22:02 ` John Stultz
2013-05-21 23:15 ` Alexander Holler
2013-05-28 19:37 ` John Stultz
2013-05-29 4:42 ` Alexander Holler
2013-06-04 13:41 ` Alexander Holler
2013-06-05 17:15 ` [PATCH 0/3] RFC: timekeeping: rtc: change hctosys mechanism Alexander Holler
2013-06-05 17:15 ` [PATCH 1/3] RFC: timekeeping: introduce flag systime_was_set Alexander Holler
2013-06-05 17:15 ` [PATCH 2/3] RFC: timekeeping: rtc: Introduce new kernel parameter hctosys Alexander Holler
2013-06-05 17:15 ` [PATCH 3/3] RFC: timekeeping: rtc: remove CONFIG_RTC_HCTOSYS and RTC_HCTOSYS_DEVICE Alexander Holler
2013-06-06 10:51 ` [PATCH 0/3 v2] RFC: timekeeping: rtc: change hctosys mechanism Alexander Holler
2013-06-06 10:51 ` [PATCH 1/3 RESEND] RFC: timekeeping: introduce flag systime_was_set Alexander Holler
2013-06-06 10:51 ` [PATCH 2/3 v2] RFC: timekeeping: rtc: Introduce new kernel parameter hctosys Alexander Holler
2013-06-13 19:39 ` Alexander Holler
2013-06-14 16:52 ` [PATCH 0/9 v3] RFC: timekeeping: rtc: change hctosys mechanism Alexander Holler
2013-06-14 16:52 ` [PATCH 1/9 RESEND] rtc: rtc-hid-sensor-time: allow full years (16bit) in HID reports Alexander Holler
2013-06-14 16:52 ` [PATCH 2/9 RESEND] rtc: rtc-hid-sensor-time: allow 16 and 32 bit values for all attributes Alexander Holler
2013-06-14 16:52 ` [PATCH 3/9] rtc: rtc-hid-sensor-time: delay registering as rtc into a work Alexander Holler
2013-06-20 10:39 ` [PATCH 3/9 v2] " Alexander Holler
2013-06-26 19:55 ` Andrew Morton
2013-06-26 21:34 ` [rtc-linux] " Alexander Holler
2013-06-26 22:07 ` Greg KH
2013-06-26 23:51 ` Alexander Holler
2013-07-06 8:55 ` Alexander Holler
2013-07-06 18:21 ` Jiri Kosina
2013-07-07 7:35 ` Alexander Holler
2013-07-08 9:12 ` [PATCH 0/2] rtc: rtc-hid-sensor-time: enable HID input processing early Alexander Holler
2013-07-08 9:12 ` [PATCH 1/2] rtc: rtc-hid-sensor-time: improve error handling when rtc register fails Alexander Holler
2013-07-08 9:12 ` [PATCH 2/2] rtc: rtc-hid-sensor-time: enable HID input processing early Alexander Holler
2013-06-28 1:29 ` [rtc-linux] Re: [PATCH 3/9 v2] rtc: rtc-hid-sensor-time: delay registering as rtc into a work Alexander Holler
2013-06-14 16:52 ` [PATCH 4/9 RESEND] RFC: timekeeping: introduce flag systime_was_set Alexander Holler
2013-06-14 17:41 ` John Stultz
2013-06-14 18:05 ` [rtc-linux] " Alexander Holler
2013-06-14 18:28 ` John Stultz
2013-06-15 6:01 ` Alexander Holler
2013-06-17 18:10 ` John Stultz
2013-06-20 10:15 ` Alexander Holler
2013-06-20 17:27 ` John Stultz
2013-06-20 18:45 ` Alexander Holler
2013-06-20 19:28 ` John Stultz
2013-06-20 23:10 ` Alexander Holler
2013-06-14 16:52 ` [PATCH 5/9 v3] RFC: timekeeping: rtc: Introduce new kernel parameter hctosys Alexander Holler
2013-06-14 19:24 ` John Stultz
2013-06-14 16:52 ` [PATCH 6/9 v3] RFC: timekeeping: rtc: remove CONFIG_RTC_HCTOSYS and RTC_HCTOSYS_DEVICE Alexander Holler
2013-06-14 19:11 ` John Stultz
2013-06-22 8:00 ` Alexander Holler
2013-06-14 16:52 ` [PATCH 7/9] RFC: rtc: implement rtc_read_timeval() Alexander Holler
2013-06-14 17:23 ` John Stultz
2013-06-14 17:43 ` Alexander Holler
2013-06-14 19:18 ` John Stultz
2013-06-14 17:28 ` John Stultz
2013-06-14 16:52 ` [PATCH 8/9] RFC: rtc: hctosys: support rtc_read_timeval() for high precision clocks Alexander Holler
2013-06-14 19:20 ` John Stultz
2013-06-14 16:52 ` [PATCH 9/9] RFC: rtc: rtc-hid-sensor-time: add support for rtc_read_timeval() Alexander Holler
2013-06-14 17:27 ` [PATCH 0/9 v3] RFC: timekeeping: rtc: change hctosys mechanism John Stultz
2013-06-06 10:51 ` [PATCH 3/3 v2] RFC: timekeeping: rtc: remove CONFIG_RTC_HCTOSYS and RTC_HCTOSYS_DEVICE Alexander Holler
2013-06-04 9:38 ` [PATCH] rtc: rtc-hid-sensor-time: fix possible bug on driver_remove Alexander Holler
2013-06-08 8:56 ` Alexander Holler
2013-05-05 11:21 ` [PATCH 4/4] rtc: rtc-hid-sensor-time: add support for milliseconds Alexander Holler
2013-04-20 23:46 ` [PATCH 0/3] rtc: rtc-hid-sensor-time Jiri Kosina
2013-04-21 6:38 ` Alexander Holler
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