linux-kernel - Re: [PATCH v2] Input: analog: Always use ktime functions

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Message-ID: <fab9f308-6677-5491-f3a7-b0ea1abd34f7@roeck-us.net>
Date:   Tue, 7 Sep 2021 05:05:09 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Dmitry Torokhov <dmitry.torokhov@...il.com>,
        linux-input <linux-input@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] Input: analog: Always use ktime functions

On 9/7/21 2:40 AM, Geert Uytterhoeven wrote:
> Hi Günter,
> 
> On Tue, Sep 7, 2021 at 8:35 AM Guenter Roeck <linux@...ck-us.net> wrote:
>> m68k, mips, s390, and sparc allmodconfig images fail to build with the
>> following error.
>>
>> drivers/input/joystick/analog.c:160:2: error:
>>          #warning Precise timer not defined for this architecture.
>>
>> Remove architecture specific time handling code and always use ktime
>> functions to determine time deltas. Also remove the now useless use_ktime
>> kernel parameter.
>>
>> Signed-off-by: Guenter Roeck <linux@...ck-us.net>
>> ---
>> v2: Drop helper functions and use ktime_get() and ktime_sub() directly
>>      Drop 'speed' variable and use NSEC_PER_MSEC directly
>>
>>   drivers/input/joystick/analog.c | 103 ++++----------------------------
>>   1 file changed, 11 insertions(+), 92 deletions(-)
>>
>> diff --git a/drivers/input/joystick/analog.c b/drivers/input/joystick/analog.c
>> index f798922a4598..a9ec41f48068 100644
>> --- a/drivers/input/joystick/analog.c
>> +++ b/drivers/input/joystick/analog.c
> 
>> @@ -275,7 +210,7 @@ static int analog_cooked_read(struct analog_port *port)
>>                  this |= data[i];
>>                  for (j = 0; j < 4; j++)
>>                          if (data[i] & (1 << j))
>> -                               port->axes[j] = (delta(start, time[i]) << ANALOG_FUZZ_BITS) / port->loop;
>> +                               port->axes[j] = (ktime_sub(time[i], start) << ANALOG_FUZZ_BITS) / port->loop;
> 
> This is now a 64-by-32 division, triggering undefined references to __udivdi3
> on some 32-bit platforms.
> 

And I was sure I checked for those. Oh well. I'll send v3 later today.

> Assumed deltas are small, the simple solution of truncating to
> 32 bit (like delta() did before):
> 
> -  port->axes[j] = (ktime_sub(time[i], start) << ANALOG_FUZZ_BITS) / port->loop;
> + port->axes[j] = ((u32)ktime_sub(time[i], start) << ANALOG_FUZZ_BITS)
> / port->loop;

Yes, I'll do that.

Thanks,
Guenter