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Subject: Re: [PATCH v3 1/2] leds: core: Introduce generic pattern interface
To:     Pavel Machek <pavel@ucw.cz>
Cc:     Baolin Wang <baolin.wang@linaro.org>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        Mark Brown <broonie@kernel.org>,
        Linux LED Subsystem <linux-leds@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
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 <20180714222924.GA2776@amd> <20180714223907.GB2776@amd>
From:   Jacek Anaszewski <jacek.anaszewski@gmail.com>
Message-ID: <1138f834-e805-6076-bb5b-aa1fdc1f2606@gmail.com>
Date:   Sun, 15 Jul 2018 14:22:03 +0200
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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.

-- 
Best regards,
Jacek Anaszewski