lkml.org 
[lkml]   [2018]   [Sep]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: [PATCH v8 1/2] leds: core: Introduce LED pattern trigger
Date
Hi Bjorn,

On 09/08/2018 07:02 AM, Bjorn Andersson wrote:
> On Tue 04 Sep 04:01 PDT 2018, Baolin Wang wrote:
>
>> diff --git a/Documentation/ABI/testing/sysfs-class-led-trigger-pattern b/Documentation/ABI/testing/sysfs-class-led-trigger-pattern
> [..]
>> +What: /sys/class/leds/<led>/hw_pattern
>> +Date: September 2018
>> +KernelVersion: 4.20
>> +Description:
>> + Specify a hardware pattern for the LED, for LED hardware that
>> + supports autonomously controlling brightness over time, according
>> + to some preprogrammed hardware patterns.
>> +
>> + Since different LED hardware can have different semantics of
>> + hardware patterns, each driver is expected to provide its own
>> + description for the hardware patterns in their ABI documentation
>> + file.
>> +
>
> So, after a full circle we're back at drivers with support for hardware
> patterns should have their own ABI for setting that pattern.
>
> The controls for my hardware is:
> * a list of brightness values
> * the rate of the pattern
> * a flag to indicate that the pattern should be played from start
> to end, end to start or start to end to start
> * a boolean indicating if the pattern should be played once or repeated
> indefinitely.
>
> Given that the interface now is hw specific, what benefit is there to
> attempt to cram these 4 knobs into "hw_pattern"? Or am I allowed to
> create additional files for the latter three?

So this is an argument corroborating my concerns raised in [0].
I really think that we should allow for custom pattern interfaces
defined by LED class drivers.

>> +What: /sys/class/leds/<led>/repeat
>> +Date: September 2018
>> +KernelVersion: 4.20
>> +Description:
>> + Specify a pattern repeat number. 0 means repeat indefinitely.
>> +
>> + This file will always return the originally written repeat
>> + number.
>
> I'm still convinced that this will confuse our users and to me it would
> be more logical if this denotes the number of times the pattern should
> be repeated, with e.g. negative numbers denoting infinite.

Sounds reasonable. Let's change this semantics as you propose.

> In particular I expect to have to explain why my driver expects that you
> write 0 in the file named "repeat" to make it repeat and 1 to make it
> not repeat.



[0] https://lkml.org/lkml/2018/9/3/1192

--
Best regards,
Jacek Anaszewski

\
 
 \ /
  Last update: 2018-09-08 22:20    [W:0.107 / U:2.216 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site