linux-kernel - Re: [PATCH v2 0/3] led: ledtrig-transient: add support for hrtimer

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Date:   Thu, 14 Sep 2017 22:03:30 +0200
From:   Jacek Anaszewski <jacek.anaszewski@...il.com>
To:     David Lin <dtwlin@...gle.com>
Cc:     Pavel Machek <pavel@....cz>, Jonathan Corbet <corbet@....net>,
        rpurdie@...ys.net, hdegoede@...hat.com,
        Greg KH <gregkh@...uxfoundation.org>, robh@...nel.org,
        Rom Lemarchand <romlem@...gle.com>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-leds@...r.kernel.org
Subject: Re: [PATCH v2 0/3] led: ledtrig-transient: add support for hrtimer

On 09/14/2017 09:38 PM, David Lin wrote:
> On Thu, Sep 14, 2017 at 12:31 PM, Jacek Anaszewski
> <jacek.anaszewski@...il.com> wrote:
>> I would change one more thing in this patch, though. The hr_timer engine
>> should be made optional and not used by default for fast LEDs.
>> It could be made configurable by exposing additional sysfs file from
>> ledtrig-transient.c, e.g. hr_timer_support, accepting boolean value.
> 
> Do you mean in additional to checking the LED_BRIGHTNESS_FAST flag,
> userspace has to explicitly enable it via sysfs for ledtrig to select
> hrtimer? This seems to be redundant to me. Could you please explain
> your concerns and the benefit of doing this? Thanks.

My concern is that fast LED users would be automatically
imposed a hr_timer overhead, which they may not need.

-- 
Best regards,
Jacek Anaszewski