From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stas Sergeev Subject: [PATCH 0/20] leds: put hard limit on minimum blink period for slow leds Date: Wed, 20 May 2015 18:17:30 +0300 Message-ID: <555CA58A.10700@list.ru> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: Sender: linux-kernel-owner@vger.kernel.org To: linux-leds@vger.kernel.org Cc: Linux kernel , Stas Sergeev List-Id: linux-leds@vger.kernel.org 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(-)