Messages in this thread | | | Date | Tue, 23 Apr 2013 12:17:29 +0200 | From | Alexander Holler <> | Subject | Re: [PATCH 3/3] rtc: rtc-hid-sensor-time; add option hctosys to set time at boot |
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Am 23.04.2013 12:13, schrieb Alexander Holler: > Am 23.04.2013 12:08, schrieb Alexander Holler: >> 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. > > Oh, damn. I've forgotten my example above with NTP. In that case setting > the time when the first RTC appears doesn't work.
So a general solution might be to set the system time when the first RTC (or the one mentioned in CONFIG_RTC_HCTOSYS_DEVICE) appears AND nothing else did set the time before.
Regards,
Alexander
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