linux-kernel - Re: [PATCH v7-incomplete 1/3] PCI: Move PRESERVE_BOOT_CONFIG _DSM evaluation to pci_register_host

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Message-ID: <ZiYVqulm8cE_FGKx@surfacebook.localdomain>
Date: Mon, 22 Apr 2024 10:45:46 +0300
From: Andy Shevchenko <andy.shevchenko@...il.com>
To: Bjorn Helgaas <helgaas@...nel.org>
Cc: Vidya Sagar <vidyas@...dia.com>,
	"Rafael J . Wysocki" <rafael@...nel.org>,
	Len Brown <lenb@...nel.org>, Will Deacon <will@...nel.org>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Rob Herring <robh@...nel.org>,
	Frank Rowand <frowand.list@...il.com>,
	Thierry Reding <treding@...dia.com>,
	Jonathan Hunter <jonathanh@...dia.com>,
	Krishna Thota <kthota@...dia.com>,
	Manikanta Maddireddy <mmaddireddy@...dia.com>,
	Vidya Sagar <sagar.tv@...il.com>, linux-pci@...r.kernel.org,
	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
	Bjorn Helgaas <bhelgaas@...gle.com>
Subject: Re: [PATCH v7-incomplete 1/3] PCI: Move PRESERVE_BOOT_CONFIG _DSM
 evaluation to pci_register_host_bridge()

Sun, Apr 21, 2024 at 02:09:12PM -0500, Bjorn Helgaas kirjoitti:
> From: Bjorn Helgaas <bhelgaas@...gle.com>
> 
> Move the PRESERVE_BOOT_CONFIG _DSM evaluation from acpi_pci_root_create()
> to pci_register_host_bridge().
> 
> This will help unify the ACPI _DSM path and the DT-based
> "linux,pci-probe-only" paths.

..

> +bool pci_acpi_preserve_config(struct pci_host_bridge *host_bridge)
> +{
> +	if (ACPI_HANDLE(&host_bridge->dev)) {

Wouldn't the below looks nicer if you invert the conditional?

	handle = ACPI_HANDLE(...);

	if (!handle)
		return false;

	...

> +		union acpi_object *obj;
> +
> +		/*
> +		 * Evaluate the "PCI Boot Configuration" _DSM Function.  If it
> +		 * exists and returns 0, we must preserve any PCI resource
> +		 * assignments made by firmware for this host bridge.
> +		 */
> +		obj = acpi_evaluate_dsm_typed(ACPI_HANDLE(&host_bridge->dev),
> +					      &pci_acpi_dsm_guid,
> +					      1, DSM_PCI_PRESERVE_BOOT_CONFIG,
> +					      NULL, ACPI_TYPE_INTEGER);
> +		if (obj && obj->integer.value == 0)
> +			return true;
> +		ACPI_FREE(obj);
> +	}
> +
> +	return false;
> +}


-- 
With Best Regards,
Andy Shevchenko