2014-11-03 16:43 GMT+03:00 Linus Walleij <[email protected]>: > On Fri, Oct 31, 2014 at 10:39 AM, Dmitry Eremin-Solenikov > <[email protected]> wrote: >> 2014-10-31 10:48 GMT+03:00 Linus Walleij <[email protected]>: >>> On Tue, Oct 28, 2014 at 1:01 AM, Dmitry Eremin-Solenikov >>> <[email protected]> wrote: >>> >>>> Add gpiolib driver for gpio pins placed on the LoCoMo GA. >>>> >>>> Signed-off-by: Dmitry Eremin-Solenikov <[email protected]> >>> >> >> [skipped] >> >>> (etc, everywhere this pattern occurs). >>>> +static void locomo_gpio_set(struct gpio_chip *chip, >>>> + unsigned offset, int value) >>>> +{ >>>> + struct locomo_gpio *lg = container_of(chip, struct locomo_gpio, >>>> gpio); >>>> + unsigned long flags; >>>> + >>>> + spin_lock_irqsave(&lg->lock, flags); >>>> + >>>> + __locomo_gpio_set(chip, offset, value); >>>> + >>>> + spin_unlock_irqrestore(&lg->lock, flags); >>> >>> If you actually always have to be getting and releasing a spin lock around >>> the register writes, contemplate using regmap-mmio because that >>> is part of what it does. >>> >>> But is this locking really necessary? >> >> I have a custom of doing such locking and never having to think about >> somebody breaking into RMW cycles. >> >> Also isn't regmap an overkill here? Wouldn't regmap also do a lock/unlock >> around each register read/write/RMW? > > Yes that's the point: if you use regmap mmio you get the RMW-locking > for free, with the regmap implementation.
Just to be more concrete. Currently locomo_gpio_ack_irq() function uses one lock and one unlock for doing 3 consecutive RMW I I convert locomo to regmap, will that be 3 lock/unlock calls or still one? (Or maybe I'm trying to be over-protective here and adding more lock/unlock cycles won't matter that much?) Next question: if I have to export regmap to several subdrivers, is it better to have one big regmap or to have one-map-per-driver approach? -- With best wishes Dmitry -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
