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SubjectRe: [PATCH v12 1/2] leds: core: Introduce LED pattern trigger
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On 09/21/2018 11:17 PM, Pavel Machek wrote:
> On Fri 2018-09-21 22:59:40, Jacek Anaszewski wrote:
>> Hi Baolin,
>>
>> On 09/21/2018 05:31 AM, Baolin Wang wrote:
>>> Hi Jacek and Pavel,
>>>
>>> On 11 September 2018 at 10:47, Baolin Wang <baolin.wang@linaro.org> wrote:
>>>> This patch adds one new led trigger that LED device can configure
>>>> the software or hardware pattern and trigger it.
>>>>
>>>> Consumers can write 'pattern' file to enable the software pattern
>>>> which alters the brightness for the specified duration with one
>>>> software timer.
>>>>
>>>> Moreover consumers can write 'hw_pattern' file to enable the hardware
>>>> pattern for some LED controllers which can autonomously control
>>>> brightness over time, according to some preprogrammed hardware
>>>> patterns.
>>>>
>>>> Signed-off-by: Raphael Teysseyre <rteysseyre@gmail.com>
>>>> Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
>
>>> Do you have any comments for the v12 patch set? Thanks.
>>
>> We will probably have to remove hw_pattern from ledtrig-pattern
>> since we are unable to come up with generic interface for it.
>> Unless thread [0] will end up with some brilliant ideas. So far
>> we're waiting for Pavel's reply.
>>
>> [0] https://lkml.org/lkml/2018/9/13/1216
>
> To paint a picture:
>
> brightness
>
> rise hold lower hold down
> ^ XXXXXXXXXXXXXXX
> | X XX
> | X XX
> | X XXXXXXXXXXXXXXXXXXXXXXXXXX
> +-------------------------------------------------------> time
>
> This is what Baolin's hardware can do, right?
>
> This is also what pattern trigger can do, right?
>
> So all we need to do is match the two interfaces, so that hw_pattern
> returns -EINVAL on patterns hardware can not actually do.
>
> I believe I described code to do that in [0] above.

You said that we should get the same effect by writing the
same series of tuples to either pattern or hw_pattern file.

Below command consists of four tuples (marked with brackets
to highlight), and it will activate breathing mode in Baolin's
hw_pattern:

"[0 rise_duration] [brightness high_duration] [brightness fall_duration]
[0 low_duration]"

Now, I can't see how these four tuples could force the software
fallback to produce breathing effect you depicted.

--
Best regards,
Jacek Anaszewski

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