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Date: Fri, 5 Jan 2024 09:44:54 +0100
From: Lukas Wunner <lukas@wunner.de>
To: Shinichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Cc: Klara Modin <klarasmodin@gmail.com>,
	"andriy.shevchenko@linux.intel.com" <andriy.shevchenko@linux.intel.com>,
	"hdegoede@redhat.com" <hdegoede@redhat.com>,
	"ilpo.jarvinen@linux.intel.com" <ilpo.jarvinen@linux.intel.com>,
	"linux-i2c@vger.kernel.org" <linux-i2c@vger.kernel.org>,
	"linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
	"platform-driver-x86@vger.kernel.org" <platform-driver-x86@vger.kernel.org>
Subject: Re: [PATCH v5 1/2] platform/x86: p2sb: Allow p2sb_bar() calls during
 PCI device probe
Message-ID: <20240105084454.GA28978@wunner.de>
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User-Agent: Mutt/1.10.1 (2018-07-13)

On Fri, Jan 05, 2024 at 08:18:05AM +0000, Shinichiro Kawasaki wrote:
> --- a/drivers/platform/x86/p2sb.c
> +++ b/drivers/platform/x86/p2sb.c
> @@ -150,6 +153,14 @@ static int p2sb_cache_resources(void)
>  	if (!bus)
>  		return -ENODEV;
>  
> +	/*
> +	 * When a device with same devfn exists and it is not P2SB, do not
> +	 * touch it.
> +	 */
> +	pci_bus_read_config_dword(bus, devfn_p2sb, PCI_CLASS_REVISION, &class);
> +	if (!PCI_POSSIBLE_ERROR(class) && class >> 8 != P2SB_CLASS_CODE)
> +		return -ENODEV;
> +

The function should probably return if PCI_POSSIBLE_ERROR() is true.
Also I think you can use PCI_CLASS_MEMORY_OTHER, so how about:

	if (PCI_POSSIBLE_ERROR(class) || class >> 16 != PCI_CLASS_MEMORY_OTHER)
		return -ENODEV;

Can alternatively use "class >> 8 != PCI_CLASS_MEMORY_OTHER << 8" if you
want to ensure the lowest byte is 0x00.

Thanks,

Lukas