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

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Message-ID: <a3fb7466-6774-4ae6-9e67-d35247ffa765@gmail.com>
Date: Mon, 18 Aug 2025 09:56:07 +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 09:54, Matti Vaittinen wrote:
> 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) {")?

Oh. Probably "if (bd71828_reg_cnt == 1)".

> 
>> +    }
>> +}
>> +
> 
> Other than that - I like this idea :)
> 
> Thanks!
> 
> Yours,
>      -- Matti