linux-kernel - Re: [PATCH v4 6/9] power: reset: macsmc-reboot: Add driver for rebooting via Apple SMC

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Message-Id: <196f84ea-6567-4fe3-9bee-743bb289223e@app.fastmail.com>
Date: Fri, 09 May 2025 18:13:09 +0200
From: "Sven Peter" <sven@...npeter.dev>
To: "Alyssa Rosenzweig" <alyssa@...enzweig.io>
Cc: "Janne Grunau" <j@...nau.net>, "Neal Gompa" <neal@...pa.dev>,
 "Hector Martin" <marcan@...can.st>,
 "Linus Walleij" <linus.walleij@...aro.org>,
 "Bartosz Golaszewski" <brgl@...ev.pl>, "Rob Herring" <robh@...nel.org>,
 "Krzysztof Kozlowski" <krzk+dt@...nel.org>,
 "Conor Dooley" <conor+dt@...nel.org>, "Sebastian Reichel" <sre@...nel.org>,
 "Lee Jones" <lee@...nel.org>, "Marc Zyngier" <maz@...nel.org>,
 "Russell King" <rmk+kernel@...linux.org.uk>, asahi@...ts.linux.dev,
 linux-arm-kernel@...ts.infradead.org,
 "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-pm@...r.kernel.org
Subject: Re: [PATCH v4 6/9] power: reset: macsmc-reboot: Add driver for rebooting via
 Apple SMC

thanks for the review!

On Fri, May 9, 2025, at 15:05, Alyssa Rosenzweig wrote:
>> +	for (i = 0; i < ARRAY_SIZE(ac_power_mode_map); i++)
>> +		if (mode == ac_power_mode_map[i])
>> +			len += scnprintf(buf+len, PAGE_SIZE-len,
>> +					 "[%s] ", ac_power_modes[i]);
>> +		else
>> +			len += scnprintf(buf+len, PAGE_SIZE-len,
>> +					 "%s ", ac_power_modes[i]);
>
> Nit: { braces } at least on the for loop...

Will fix that.

>
> (And might be more concise as
>
>     for (i = 0; i < ARRAY_SIZE(ac_power_mode_map); i++) {
>         bool match = (mode == ac_power_mode_map[i]);
>         len += scnprintf(buf+len, PAGE_SIZE-len,
>                  match ? "[%s] " : "%s ", ac_power_modes[i]);
>     }
>
> though IDK how people feel about it.)

imho it's less readable that way but I don't have a strong opinion
either way.

>
>> +		mdelay(100);
>> +		WARN_ON(1);
>
> ...What?

This is done in a few drivers in drivers/power/reboot. If we haven't
rebooted after 100ms something's wrong with SMC. I'll add a comment.

drivers/power/reset/tps65086-restart.c:	WARN_ON(1);
drivers/power/reset/atc260x-poweroff.c:	WARN_ONCE(1, "Unable to power off system\n");
drivers/power/reset/mt6323-poweroff.c:	WARN_ONCE(1, "Unable to power off system\n");
drivers/power/reset/gpio-restart.c:	WARN_ON(1);
drivers/power/reset/regulator-poweroff.c:	WARN_ON(1);



>
>> +	if (ret)
>> +		return dev_err_probe(&pdev->dev, ret,
>> +				     "Failed to register power-off handler\n");
>> +
>> +
>> +	ret = devm_register_sys_off_handler(&pdev->dev, SYS_OFF_MODE_RESTART_PREPARE,
>> +					    SYS_OFF_PRIO_HIGH, macsmc_prepare_atomic, reboot);
>
> Nit: squash double blank-line

will do.


thanks,


Sven