Re: [PATCH v2 2/5] gpio: Introduce ->get_multiple callback

[Linus Walleij <linus.walleij@xxxxxxxxxx>]

On Thu, Oct 12, 2017 at 12:40 PM, Lukas Wunner <lukas@xxxxxxxxx> wrote:

> SPI-attached GPIO controllers typically read out all inputs in one go.
> If callers desire the values of multipe inputs, ideally a single readout
> should take place to return the desired values.  However the current
> driver API only offers a ->get callback but no ->get_multiple (unlike
> ->set_multiple, which is present).  Thus, to read multiple inputs, a
> full readout needs to be performed for every single value (barring
> driver-internal caching), which is inefficient.
>
> In fact, the lack of a ->get_multiple callback has been bemoaned
> repeatedly by the gpio subsystem maintainer:
> http://www.spinics.net/lists/linux-gpio/msg10571.html
> http://www.spinics.net/lists/devicetree/msg121734.html
>
> Introduce the missing callback.  Add corresponding consumer functions
> such as gpiod_get_array_value().  Amend linehandle_ioctl() to take
> advantage of the newly added infrastructure.  Update the documentation.
>
> Cc: Rojhalat Ibrahim <imr@xxxxxxxxxxx>
> Signed-off-by: Lukas Wunner <lukas@xxxxxxxxx>
> ---
> Changes v1 -> v2:

Applied this v2 version.

Good work! I'm happy :)

We should take a sweep over existing drivers and see
which in-tree drivers that can exploit this and send some
patches for testing.

Yours,
Linus Walleij
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