Hi George,
On Sat, Jul 21, 2012 at 11:42:28PM -0400, George Spelvin wrote:
> This replaces some inaccurate lookup tables with an exact
> computation. Although the diff adds source comments,
> it shrinks binary size. (By only 50 bytes, but hey.)
>
> AT keyboard repeat rates are multiples of 1/240 second
> expressed in a 0.2.3 bit floating point format. That
> is, possible values are ({8..15} << {0..3}) / 240 s.
OK.
>
> In addition to a slightly inaccurate lookup table, the
> old code would round up to the next repeat period.
> E.g. to get a period of 9/60 = 0.15 seconds, you had to
> ask for no more than 149 ms; if you asked for 150, it
> would round up to 167.
This works as intended - it was designed to never have faster than
requested.
> The new code rounds to nearest.
>
> User-visible changes to the repeat periods reported by EVIOCGREP:
>
> Old 37 109 116 149 182 232
> Exact 37.50 108.33 116.66 150.00 183.33 233.33
> New 38 108 117 150 183 233
>
> Old 270 303 370 435 470
> Exact 266.66 300.00 366.66 433.33 466.66
> New 267 300 367 433 467
>
> This does not bother utilities like kbdrate(8).
>
> Signed-off-by: George Spelvin <linux@xxxxxxxxxxx>
I am sorry but I have to ask - is this your real name?
> ---
> drivers/input/keyboard/atkbd.c | 47 +++++++++++++++++++++++++++++++----------------
> 1 file changed, 31 insertions(+), 16 deletions(-)
>
> Now that 3.5 is out, I'm posting this for a FOURTH time,
> hoping for some comments of any sort.
>
>
> Now that I've tweaked it (v1 had an error in rounding near exponent
> range boundaries), I think it's ready for merging upstream.
>
>
> One possible bug I observed in the code that calls this:
>
> Users of the KDKBDREP ioctl seem to assume that it returns the actual
> values set, but I'm not sure it really works that way; I don't think
> the command to change the parameters makes its way through the event
> queue and atkbd's schedule_delayed_work() to actually set dev->rep[]
> to the rounded values before kbd_rate_helper returns them to userspace.
>
> If desired, the fix that's most obvious to me would be to split this
> function in two: perform the conversion to a command byte synchronously,
> and only defer the actual ps2_command().
Yes, I agree, this is a problem.
Thanks.
--
Dmitry
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