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Currently, led pattern trigger uses timer_list to schedule brightness changing. As we know from timer_list API [1], it's not accurate to milliseconds and depends on HZ granularity. Example: "0 10 0 0 50 10 50 0 100 10 100 0 150 10 150 0 200 10 200 0 250 10 250 0", we expect it to be 60ms long, but it can actually be up to ~120ms (add ~10ms for each pattern when HZ == 100). But sometimes, userspace needs time accurate led patterns to make sure that pattern will be executed during expected time slot. To achieve this goal the patch introduces optional hrtimer usage for led trigger pattern, because hrtimer is microseconds accurate timer. [1]: kernel/time/timer.c#L104 Signed-off-by: Martin Kurbanov <mmkurbanov@salutedevices.com> Link: https://lore.kernel.org/r/20240416201847.357099-1-mmkurbanov@salutedevices.com Signed-off-by: Lee Jones <lee@kernel.org>
51 lines
1.7 KiB
Plaintext
51 lines
1.7 KiB
Plaintext
What: /sys/class/leds/<led>/pattern
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Date: September 2018
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KernelVersion: 4.20
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Description:
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Specify a software pattern for the LED, that supports altering
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the brightness for the specified duration with one software
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timer. It can do gradual dimming and step change of brightness.
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The pattern is given by a series of tuples, of brightness and
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duration (ms).
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The exact format is described in:
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Documentation/devicetree/bindings/leds/leds-trigger-pattern.txt
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What: /sys/class/leds/<led>/hr_pattern
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Date: April 2024
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Description:
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Specify a software pattern for the LED, that supports altering
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the brightness for the specified duration with one software
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timer. It can do gradual dimming and step change of brightness.
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Unlike the /sys/class/leds/<led>/pattern, this attribute runs
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a pattern on high-resolution timer (hrtimer).
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What: /sys/class/leds/<led>/hw_pattern
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Date: September 2018
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KernelVersion: 4.20
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Description:
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Specify a hardware pattern for the LED, for LED hardware that
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supports autonomously controlling brightness over time, according
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to some preprogrammed hardware patterns. It deactivates any active
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software pattern.
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Since different LED hardware can have different semantics of
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hardware patterns, each driver is expected to provide its own
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description for the hardware patterns in their documentation
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file at Documentation/leds/.
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What: /sys/class/leds/<led>/repeat
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Date: September 2018
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KernelVersion: 4.20
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Description:
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Specify a pattern repeat number. -1 means repeat indefinitely,
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other negative numbers and number 0 are invalid.
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This file will always return the originally written repeat
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number.
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It should be noticed that some leds, like EL15203000 may
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only support indefinitely patterns, so they always store -1.
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