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

[Alexandre Courbot <gnurou@xxxxxxxxx>]

On Mon, Jun 16, 2014 at 10:51 PM, Rojhalat Ibrahim <imr@xxxxxxxxxxx> wrote:
> 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.

Tried to find something more to say, but each and every concern I had
has been addressed through the various revisions of this series.

Reviewed-by: Alexandre Courbot <acourbot@xxxxxxxxxx>

As far as I can judge, this is a very nicely crafted patch.
--
To unsubscribe from this list: send the line "unsubscribe linux-gpio" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html