linux-kernel - Re: [PATCH v3 1/2] leds: core: Introduce generic pattern interface

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Message-ID: <CAMz4kuKw+nQp55w5XeNYE3TVq1KnQFG3-yEsG4vANqu4yC3CTA@mail.gmail.com>
Date:   Mon, 16 Jul 2018 19:08:58 +0800
From:   Baolin Wang <baolin.wang@...aro.org>
To:     Jacek Anaszewski <jacek.anaszewski@...il.com>
Cc:     Pavel Machek <pavel@....cz>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Mark Brown <broonie@...nel.org>,
        Linux LED Subsystem <linux-leds@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 1/2] leds: core: Introduce generic pattern interface

On 15 July 2018 at 20:22, Jacek Anaszewski <jacek.anaszewski@...il.com> wrote:
> On 07/15/2018 12:39 AM, Pavel Machek wrote:
>>
>> On Sun 2018-07-15 00:29:25, Pavel Machek wrote:
>>>
>>> On Sun 2018-07-15 00:02:57, Jacek Anaszewski wrote:
>>>>
>>>> Hi Pavel,
>>>>
>>>> On 07/14/2018 11:20 PM, Pavel Machek wrote:
>>>>>
>>>>> Hi!
>>>>>
>>>>>>> It also drew my attention to the issue of desired pattern sysfs
>>>>>>> interface semantics on uninitialized pattern. In your implementation
>>>>>>> user seems to be unable to determine if the pattern is activated
>>>>>>> or not. We should define the semantics for this use case and
>>>>>>> describe it in the documentation. Possibly pattern could
>>>>>>> return alone new line character then.
>>>>>
>>>>>
>>>>> Let me take a step back: we have triggers.. like LED blinking.
>>>>>
>>>>> How is that going to interact with patterns? We probably want the
>>>>> patterns to be ignored in that case...?
>>>>>
>>>>> Which suggest to me that we should treat patterns as a trigger. I
>>>>> believe we do something similar with blinking already.
>>>>>
>>>>> Then it is easy to determine if pattern is active, and pattern
>>>>> vs. trigger issue is solved automatically.
>>>>
>>>>
>>>> I'm all for it. I proposed this approach during the previous
>>>> discussions related to possible pattern interface implementations,
>>>> but you seemed not to be so enthusiastic in [0].
>>>>
>>>> [0] https://lkml.org/lkml/2017/4/7/350
>>>
>>>
>>> Hmm. Reading my own email now, I can't decipher it.
>>>
>>> I believe I meant "changing patterns from kernel in response to events
>>> is probably overkill"... or something like that.
>>
>>
>> Anyway -- to clean up the confusion -- I'd like to see
>>
>> echo pattern > trigger
>> echo "1 2 3 4 5 6 7 8" > somewhere
>
>
> s/somewhere/pattern/
>
> pattern trigger should create "pattern" file similarly how ledtrig-timer
> creates delay_{on|off} files.

Yes. Anyway, I will submit V5 patchset with addressing previous
comments, but did not include pattern trigger issue.

-- 
Baolin Wang
Best Regards