From: Rojhalat Ibrahim Date: Tue, 4 Nov 2014 16:12:06 +0000 (+0100) Subject: gpiolib: allow simultaneous setting of multiple GPIO outputs X-Git-Tag: omap-for-v3.20/drop-legacy-3517~86^2~17 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=5f42424354f5b0ca5413b4fb8528d150692c85b7;p=pandora-kernel.git gpiolib: allow simultaneous setting of multiple GPIO outputs Introduce new functions gpiod_set_array & gpiod_set_raw_array to the consumer interface which allow setting multiple outputs with just one function call. Also add an optional set_multiple function to the driver interface. Without an implementation of that function in the chip driver outputs are set sequentially. Implementing the set_multiple function in a chip driver allows for: - Improved performance for certain use cases. The original motivation for this was the task of configuring an FPGA. In that specific case, where 9 GPIO lines have to be set many times, configuration time goes down from 48 s to 20 s when using the new function. - Simultaneous glitch-free setting of multiple pins on any kind of parallel bus attached to GPIOs provided they all reside on the same chip and bank. Limitations: Performance is only improved for normal high-low outputs. Open drain and open source outputs are always set separately from each other. Those kinds of outputs could probably be accelerated in a similar way if we could forgo the error checking when setting GPIO directions. Change log: v6: - rebase on current linux-gpio devel branch v5: - check can_sleep property per chip - remove superfluous checks - supplement documentation v4: - add gpiod_set_array function for setting logical values - change interface of the set_multiple driver function to use unsigned long as type for the bit fields - use generic bitops (which also use unsigned long for bit fields) - do not use ARCH_NR_GPIOS any more v3: - add documentation - change commit message v2: - use descriptor interface - allow arbitrary groups of GPIOs spanning multiple chips Signed-off-by: Rojhalat Ibrahim Reviewed-by: Alexandre Courbot Reviewed-by: Mark Brown Signed-off-by: Linus Walleij --- Reading git-diff-tree failed