Re: [PATCH 1/2][v5] gpiolib: allow simultaneous setting of multiple GPIO outputs

[Linus Walleij <linus.walleij@xxxxxxxxxx>]

On Thu, Jul 31, 2014 at 10:42 AM, Rojhalat Ibrahim <imr@xxxxxxxxxxx> wrote:
> On Thursday 31 July 2014 09:12:35 Gerhard Sittig wrote:
>> On Thu, 2014-07-31 at 11:35 +0900, Alexandre Courbot wrote:
>> >
>> > I'd be surprised if at least *one* such driver was not in mainline
>> > though. Had a quick look but could not find anything that would be an
>> > obvious candidate to use these new functions.
>>
>> What about drivers/mtd/nand/gpio.c, the GPIO bitbanged NAND
>> controller driver?  Most of the latch, control, and data lines
>> groups are set at the same time.  It should be a perfect example.
>>
>
> Well, not so perfect, since AFAIUI only a few control signals are managed
> by GPIOs (Chip Enable, Command Latch Enable, Address Latch Enable), but not
> the actual data lines. But granted, at least at one place in the driver three
> lines are set at the same time.
>
> There are a few other drivers which also do that:
> - drivers/tty/serial/serial_mctrl_gpio.c controls multiple modem lines via GPIO
> - drivers/net/phy/mdio-mux-gpio.c a GPIO controlled MDIO bus multiplexer driver
> - drivers/regulator/gpio-regulator.c controls voltage regulators
>
> All of the above do set multiple GPIOs at the same time, but in all cases
> performance does not really matter. Moreover they all seem a bit obscure to me.
>
> Nevertheless, IMHO they are still better candidates for using the new functions
> than the i2c-gpio or spi-gpio drivers.
>
> So, Linus, would a patched version of one of the mentioned drivers qualify as
> a user that would allow you to merge my patch?

I think so. My concern is with code that doesn't get exercised, anywhere.

Yours,
Linus Walleij
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