linux-kernel - [PATCH 0/20] leds: put hard limit on minimum blink period for slow leds

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Date:	Wed, 20 May 2015 18:17:30 +0300
From:	Stas Sergeev <stsp@...t.ru>
To:	linux-leds@...r.kernel.org
CC:	Linux kernel <linux-kernel@...r.kernel.org>,
	Stas Sergeev <stsp@...rs.sourceforge.net>
Subject: [PATCH 0/20] leds: put hard limit on minimum blink period for slow
 leds


Currently the timer trigger allows to set blink period as small as
1mS. But in fact the minimum period is jiffy, which is usually 10mS.
The following mail says:
http://lkml.iu.edu/hypermail/linux/kernel/1504.3/03469.html
<<
As I mentioned before even with hr timer it wouldn't be possible
to assure that 1ms is achievable due to locking and bus latency
reasons.
>>
So the limit of 10mS should be enforced for drivers that use
waiting operations, like transfers across slow bus.
This allows to stay on safe side when CONFIG_HZ is set to eg 1000.

This patch set differentiates the "fast" drivers by marking them
with the new LED_BRIGHTNESS_FAST flag. For these drivers, setting
periods as small as 1mS is possible (provided CONFIG_HZ is set
appropriately), while for "slow" drivers the limit of 10mS in enforced.
In the future, the "fast" drivers may get used by a software PWM.


 drivers/leds/dell-led.c                |    2 +-
 drivers/leds/led-core.c                |   30 +++++++++++++++++++-----------
 drivers/leds/led-triggers.c            |    8 +++++---
 drivers/leds/leds-asic3.c              |    2 +-
 drivers/leds/leds-bcm6328.c            |    1 +
 drivers/leds/leds-clevo-mail.c         |    2 +-
 drivers/leds/leds-cobalt-qube.c        |    1 +
 drivers/leds/leds-cobalt-raq.c         |    2 ++
 drivers/leds/leds-fsg.c                |   12 ++++++------
 drivers/leds/leds-gpio.c               |    2 ++
 drivers/leds/leds-hp6xx.c              |    4 ++--
 drivers/leds/leds-locomo.c             |    2 ++
 drivers/leds/leds-net48xx.c            |    2 +-
 drivers/leds/leds-netxbig.c            |    2 +-
 drivers/leds/leds-ns2.c                |    2 +-
 drivers/leds/leds-ot200.c              |    1 +
 drivers/leds/leds-pwm.c                |    2 ++
 drivers/leds/leds-s3c24xx.c            |    2 +-
 drivers/leds/leds-ss4200.c             |    1 +
 drivers/leds/leds-versatile.c          |    1 +
 drivers/leds/leds-wrap.c               |    6 +++---
 drivers/leds/trigger/ledtrig-oneshot.c |    5 ++++-
 drivers/leds/trigger/ledtrig-timer.c   |   18 +++++++++++++-----
 include/linux/leds.h                   |   12 ++++++++++--
 24 files changed, 82 insertions(+), 40 deletions(-)
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