Messages in this thread Patch in this message | | | Date | Wed, 17 Sep 2014 21:23:37 +0200 | From | Andreas Mohr <> | Subject | Re: [PATCH v2] Input: joystick - Use ktime for measuring timing |
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Hi,
On Wed, Sep 10, 2014 at 05:57:17PM +0200, Takashi Iwai wrote: > The current codes in gameport and analog joystick drivers for the time > accounting have a long-standing problem when the system is running > with CPU freq; since the timing is measured via TSC or sample counter, > the calculation isn't reliable.
Thank you very much for having followed through on this! (somehow you never seem to disappoint me :)
While working on testing this and doing various gameport/soundcard modifications, I'm afraid I have seen the following checkpatch.pl (of v3.16) warnings:
WARNING: Missing a blank line after declarations #164: FILE: drivers/input/joystick/analog.c:192: + unsigned int x; + GET_TIME(x);
WARNING: line over 80 characters #224: FILE: drivers/input/joystick/analog.c:301: + port->axes[j] = (delta(start, time[i]) << ANALOG_FUZZ_BITS) / port->loop;
BTW the commit as-is will not be compatible with v3.16 since there's no ktime_get_ns() there yet and (to add insult to injury) even the #include header files have changed, too.
That's a bit of a pity since I just had intended to say that it's a very good idea to release a quick(&dirty) initial timing hotfix for gameport handling *prior* to possibly doing any subsequent less-related gameport cleanup commits, since the quick initial timing hotfix would be very prominent -stable material, except it... ain't so (--> life sucks :-).
So, for -stable reasons it might be very worthwhile to add some compat code to the analog.c patch - I am currently using the following compat fix (on v3.16):
--- a/drivers/input/joystick/analog.c +++ b/drivers/input/joystick/analog.c @@ -36,7 +36,14 @@ #include <linux/gameport.h> #include <linux/jiffies.h> #include <linux/timex.h> -#include <linux/timekeeping.h> +//#include <linux/timekeeping.h> +#include <linux/hrtimer.h> + +static inline u64 ktime_get_ns(void) +{ + return ktime_to_ns(ktime_get()); +} +
(which obviously isn't fit for purpose yet since you'd need a versioned #include conditional, and the name of this function when unconditionally added is in direct conflict with the same-name > v3.16 one)
So, should that commit be improved to have a simple versioning check in order to be fully -stable deployable, or would -stable be handled differently anyway? (I'll now have these updates and checkpatch.pl stuff maintained in a FIXUP commit locally)
So much for a quick status update (I'll be rebooting into 3.16 now - my last kernel build was as low as 3.11.x even, WOW).
Thanks,
Andreas Mohr
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