[U-Boot] [PATCH 06/13] gpio: add support for new flags on gpio configuration

[Simon Glass]

Hi Patrick,

On Wed, 23 Oct 2019 at 07:45, Patrick Delaunay <patrick.delaunay at st.com> wrote:
>
> This commit manages the flags that can be used in GPIO specifiers to
> indicate if a pull-up resistor or pull-down resistor should be
> enabled for output GPIO and the Open Drain/Open Source configuration
> for input GPIO.
>
> It is managed in driver with a new ops in gpio uclass set_config.
>
> These flags are already support in Linux kernel in gpiolib.
>
> Signed-off-by: Patrick Delaunay <patrick.delaunay at st.com>
> ---
>
>  drivers/gpio/gpio-uclass.c | 62 +++++++++++++++++++++++++++++++++++++-
>  include/asm-generic/gpio.h | 56 ++++++++++++++++++++++++++++++++++
>  2 files changed, 117 insertions(+), 1 deletion(-)
>

To me this seems like a pretty annoying interface. The uclass has to
call the driver multiple times with each enum and the driver may end
up reprogramming the pins multiple times to get it right.

Normally we want to program things correctly once, before enabling the function.

On the other handle I think what you have is better than adding new
methods like set_open_drain().

But overall I think it would be better to define a new struct like
gpio_config that holds some flags and perhaps a few other things. Then
the uclass can set up that struct and call the driver once with it, to
set up the pin. It could include input/output too, so that if
set_config() is defined, the uclass uses that instead of
direction_output(), etc.

What do you think?

Also we should update the sandbox driver to include tests for new
methods. It looks like you have done pinctrl but not this?

Regards,
Simon