linux-kernel - Re: [PATCH v2 2/5] PCI/pwrctl: Create pwrctl devices only if at least one power supply is present

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Message-ID: <20241106212826.GA1540916@bhelgaas>
Date: Wed, 6 Nov 2024 15:28:26 -0600
From: Bjorn Helgaas <helgaas@...nel.org>
To: manivannan.sadhasivam@...aro.org
Cc: Bjorn Helgaas <bhelgaas@...gle.com>,
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>,
	Bartosz Golaszewski <brgl@...ev.pl>, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
	Johan Hovold <johan+linaro@...nel.org>,
	Abel Vesa <abel.vesa@...aro.org>,
	Stephan Gerhold <stephan.gerhold@...aro.org>,
	Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
	Bjorn Andersson <bjorn.andersson@....qualcomm.com>,
	stable+noautosel@...nel.org,
	Krishna chaitanya chundru <quic_krichai@...cinc.com>
Subject: Re: [PATCH v2 2/5] PCI/pwrctl: Create pwrctl devices only if at
 least one power supply is present

On Fri, Oct 25, 2024 at 01:24:52PM +0530, Manivannan Sadhasivam via B4 Relay wrote:
> From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> 
> Currently, pwrctl devices are created if the corresponding PCI nodes are
> defined in devicetree. But this is not correct, because not all PCI nodes
> defined in devicetree require pwrctl support. Pwrctl comes into picture
> only when the device requires kernel to manage its power state. This can
> be determined using the power supply properties present in the devicetree
> node of the device.

> +bool of_pci_is_supply_present(struct device_node *np)
> +{
> +	struct property *prop;
> +	char *supply;
> +
> +	if (!np)
> +		return false;

Why do we need to test !np here?  It should always be non-NULL.

> +	for_each_property_of_node(np, prop) {
> +		supply = strrchr(prop->name, '-');
> +		if (supply && !strcmp(supply, "-supply"))
> +			return true;
> +	}
> +
> +	return false;
> +}