[BRLTTY] gettimeofday

[Vladimir 'φ-coder/phcoder' Serbinenko]

On 18.06.2012 15:20, Dave Mielke wrote:

> [quoted lines by Vladimir 'φ-coder/phcoder' Serbinenko on 2012/06/18 at 14:39 +0200]
> 
>> Previously it was discussed how to make an equivalent of gettimeofday to
>> work on GRUB. 
> 
> Yes. You may wish to check timing:getCurrentTime() to see if we got it right 
> for grub.
> 

I'll look into it.

>> Now, I've realized that the current code using gettimeofday is wrong since the 
>> date gives no guaranty of being monotonic, and especially it isn't if someone 
>> runs "date" or "ntpdate" which is common operation, especially on systems 
>> where the RTC battery is failing. 
> 
> And during daylight saving time switches. :-)
> 

Unless you use UTC.

>> brltty should use time/gettimeofday only for timestamping logs and 
>> CLOCK_MONOTONIC (probably with some wrapper to make other monotonic clock 
>> sources easy to add) for all timing and timeout purposes. 
> 
> Yes, thanks, for timeouts that's an excellent point. I doubt CLOCK_MONOTONIC 
> existed way back whenever, but, yes, we really should fix this. We can always 
> code the current method as a fallback for builds on old systems.
> 
> What should we be using within the Grub environment for this?

grub_get_time_ms. On modern X86 it's based on TSC.

> 



-- 
Regards
Vladimir 'φ-coder/phcoder' Serbinenko

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