Re: [RFT PATCH v2] spi: bcm2835: reduce the abuse of the GPIO API

[Linus Walleij <linus.walleij@xxxxxxxxxx>]

On Fri, Sep 1, 2023 at 1:15 PM Bartosz Golaszewski <brgl@xxxxxxxx> wrote:

> From: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>
>
> Currently the bcm2835 SPI driver uses functions that are available
> exclusively to GPIO providers as a way to handle a platform quirk. Let's
> use a slightly better alternative that avoids poking around in GPIOLIB's
> internals and use GPIO lookup tables.
>
> Link: https://www.spinics.net/lists/linux-gpio/msg36218.html
> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>

> +#include <linux/cleanup.h>
(...)
> -       struct gpio_chip *chip;
> +       struct gpiod_lookup_table *lookup __free(kfree) = NULL;

Whoa!
This is really neat.
As noted, it will confuse static checkers at no end, but they just have
to adopt. (CC to Dan C if he now runs into this.)

> +       gpiod_add_lookup_table(lookup);

Maybe we should mention the obvious advantage to the previous
hack: if there is a "cs-gpios" in the device tree, it will take precedence,
because gpiod_find_and_request() will try gpiod_find_by_fwnode()
*first* and only if this fails it will fall back to gpiod_find().

Hm, maybe we should go and fix these device trees? :P

Reviewed-by: Linus Walleij <linus.walleij@xxxxxxxxxx>

Yours,
Linus Walleij