linux-kernel - Re: [PATCH v3 07/10] gpio: aggregator: export symbols of the GPIO forwarder library

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Message-ID: <aAE7akcsktz1wc2w@smile.fi.intel.com>
Date: Thu, 17 Apr 2025 20:33:30 +0300
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Thomas Richard <thomas.richard@...tlin.com>
Cc: Linus Walleij <linus.walleij@...aro.org>,
	Bartosz Golaszewski <brgl@...ev.pl>,
	Geert Uytterhoeven <geert+renesas@...der.be>,
	linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
	thomas.petazzoni@...tlin.com, DanieleCleri@...on.eu,
	GaryWang@...on.com.tw
Subject: Re: [PATCH v3 07/10] gpio: aggregator: export symbols of the GPIO
 forwarder library

On Wed, Apr 16, 2025 at 04:08:15PM +0200, Thomas Richard wrote:
> Export all symbols and create header file for the GPIO forwarder library.

...

> -struct gpiochip_fwd_timing {
> -	u32 ramp_up_us;
> -	u32 ramp_down_us;
> -};
> -
> -struct gpiochip_fwd {
> -	struct gpio_chip chip;
> -	struct gpio_desc **descs;
> -	union {
> -		struct mutex mlock;	/* protects tmp[] if can_sleep */
> -		spinlock_t slock;	/* protects tmp[] if !can_sleep */
> -	};
> -	struct gpiochip_fwd_timing *delay_timings;
> -	unsigned long tmp[];		/* values and descs for multiple ops */
> -};

I don't like this piece at all. It will repeat one of the biggest mistake done
with many (old) subsystems and core.

Looking at the last patch ahead, I can tell that this is not needed. Instead
add a couple of APIs:
- getter for the gpiochip
- getter for the specific private data

and use the error code filtering for the existed GPIO descriptor, I actually
don't understand why for the existed descriptor you return there 0 and not an
error.

TL;DR: Follow OOP and make this an opaque pointer, no need to move it to the
header. The rest looks okay on the first glance.

-- 
With Best Regards,
Andy Shevchenko