linux-kernel - Re: [PATCH v19 06/10] power: reset: Add psci-reboot-mode driver

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Message-ID: <CAMRc=Me8WQ=aMd-NJ1yzzHzqU8fT1u4eb7as=EjSpZ+Rpv9+rg@mail.gmail.com>
Date: Fri, 2 Jan 2026 12:57:47 +0100
From: Bartosz Golaszewski <brgl@...nel.org>
To: Shivendra Pratap <shivendra.pratap@....qualcomm.com>
Cc: Lorenzo Pieralisi <lpieralisi@...nel.org>, Arnd Bergmann <arnd@...db.de>, 
	Bjorn Andersson <andersson@...nel.org>, Sebastian Reichel <sre@...nel.org>, Rob Herring <robh@...nel.org>, 
	Sudeep Holla <sudeep.holla@....com>, Souvik Chakravarty <Souvik.Chakravarty@....com>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Andy Yan <andy.yan@...k-chips.com>, 
	John Stultz <john.stultz@...aro.org>, Matthias Brugger <matthias.bgg@...il.com>, 
	Moritz Fischer <moritz.fischer@...us.com>, Mark Rutland <mark.rutland@....com>, 
	Conor Dooley <conor+dt@...nel.org>, Konrad Dybcio <konradybcio@...nel.org>, 
	Florian Fainelli <florian.fainelli@...adcom.com>, Krzysztof Kozlowski <krzk@...nel.org>, 
	Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>, 
	Mukesh Ojha <mukesh.ojha@....qualcomm.com>, Andre Draszik <andre.draszik@...aro.org>, 
	Kathiravan Thirumoorthy <kathiravan.thirumoorthy@....qualcomm.com>, linux-pm@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org, 
	Srinivas Kandagatla <srini@...nel.org>
Subject: Re: [PATCH v19 06/10] power: reset: Add psci-reboot-mode driver

On Sun, Dec 28, 2025 at 6:21 PM Shivendra Pratap
<shivendra.pratap@....qualcomm.com> wrote:
>

[snip]

> +
> +static int psci_reboot_mode_probe(struct faux_device *fdev)
> +{
> +       struct reboot_mode_driver *reboot;
> +       struct device_node *psci_np;
> +       struct device_node *np;
> +       int ret;
> +
> +       psci_np = of_find_compatible_node(NULL, NULL, "arm,psci-1.0");
> +       if (!psci_np)
> +               return -ENODEV;
> +
> +       /*
> +        * Find the psci:reboot-mode node.
> +        * If NULL, continue to register predefined modes.
> +        * np refcount to be handled by dev;
> +        * psci_np refcount is decremented by of_find_node_by_name;
> +        */

Can you make this comment into full sentences, I had trouble parsing
the meaning for a minute.

> +       np = of_find_node_by_name(psci_np, "reboot-mode");
> +       fdev->dev.of_node = np;

The logic of the device assigning its own node is a bit sketchy,
ideally this should be done before the device probes.

> +
> +       reboot = devm_kzalloc(&fdev->dev, sizeof(*reboot), GFP_KERNEL);
> +       if (!reboot)
> +               return -ENOMEM;
> +
> +       psci_reboot_mode_set_predefined_modes(reboot);
> +       reboot->write = psci_reboot_mode_write;
> +       reboot->dev = &fdev->dev;
> +
> +       ret = devm_reboot_mode_register(&fdev->dev, reboot);
> +       if (ret) {
> +               dev_err(&fdev->dev, "devm_reboot_mode_register failed %d\n", ret);
> +               return ret;

Use dev_err_probe().

> +       }
> +
> +       return 0;
> +}
> +
> +static struct faux_device_ops psci_reboot_mode_ops = {
> +       .probe = psci_reboot_mode_probe,
> +};
> +
> +static int __init psci_reboot_mode_init(void)
> +{
> +       struct faux_device *fdev;
> +
> +       fdev = faux_device_create("psci-reboot-mode", NULL, &psci_reboot_mode_ops);
> +       if (!fdev)
> +               return -ENODEV;

This will always create this device for everyone who includes this
module. Move the of_find_compatible_node(NULL, NULL, "arm,psci-1.0")
call from probe() here instead and don't create the device if it
fails.

Bart

> +
> +       return 0;
> +}
> +device_initcall(psci_reboot_mode_init);
>
> --
> 2.34.1
>