linux-kernel - Re: [PATCH 2/3] mfd: rohm-bd71828: Use software nodes for gpio-keys

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Message-ID: <0adb5e0a-ea37-4bd5-87ff-654b770261f2@gmail.com>
Date: Mon, 18 Aug 2025 09:54:12 +0300
From: Matti Vaittinen <mazziesaccount@...il.com>
To: Dmitry Torokhov <dmitry.torokhov@...il.com>, Lee Jones <lee@...nel.org>
Cc: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
 Arnd Bergmann <arnd@...nel.org>, Bartosz Golaszewski <brgl@...ev.pl>,
 Linus Walleij <linus.walleij@...aro.org>, linux-input@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] mfd: rohm-bd71828: Use software nodes for gpio-keys

On 18/08/2025 01:47, Dmitry Torokhov wrote:
> Refactor the rohm-bd71828 MFD driver to use software nodes for
> instantiating the gpio-keys child device, replacing the old
> platform_data mechanism.

Thanks for doing this Dmitry! I believe I didn't understand how 
providing the IRQs via swnode works... :)

If I visit the ROHM office this week, then I will try to test this using 
the PMIC HW. (Next week I'll be in ELCE, and after it I have probably 
already forgotten this...)

> The power key's properties are now defined using software nodes and
> property entries. The IRQ is passed as a resource attached to the
> platform device.
> 
> This will allow dropping support for using platform data for configuring
> gpio-keys in the future.
> 
> Signed-off-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
> ---
>   drivers/mfd/rohm-bd71828.c | 81 +++++++++++++++++++++++++++-----------
>   1 file changed, 58 insertions(+), 23 deletions(-)
> 
> diff --git a/drivers/mfd/rohm-bd71828.c b/drivers/mfd/rohm-bd71828.c
> index a14b7aa69c3c..c29dde9996b7 100644
> --- a/drivers/mfd/rohm-bd71828.c
> +++ b/drivers/mfd/rohm-bd71828.c
> @@ -4,7 +4,6 @@

// ...snip

>   
> +static int bd71828_reg_cnt;
> +
> +static int bd71828_i2c_register_swnodes(void)
> +{
> +	int error;
> +
> +	if (bd71828_reg_cnt == 0) {

Isn't this check racy...

> +		error = software_node_register_node_group(bd71828_swnodes);
> +		if (error)
> +			return error;
> +	}
> +
> +	bd71828_reg_cnt++;

... with this...

> +	return 0;
> +}
> +
> +static void bd71828_i2c_unregister_swnodes(void *dummy)
> +{
> +	if (bd71828_reg_cnt != 0) {

...this...

> +		software_node_unregister_node_group(bd71828_swnodes);
> +		bd71828_reg_cnt--;

...and this? Perhaps add a mutex or use atomics?

Also, shouldn't the software_node_unregister_node_group() be only called 
for the last instance to exit (Eg, "if (bd71828_reg_cnt == 0)" instead 
of the "if (bd71828_reg_cnt != 0) {")?

> +	}
> +}
> +

Other than that - I like this idea :)

Thanks!

Yours,
	-- Matti