linux-kernel - Re: [PATCH v3] PCI/DOE: Expose the DOE protocols via sysfs

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Date:   Thu, 10 Aug 2023 09:34:57 +0200
From:   Lukas Wunner <lukas@...ner.de>
To:     Alistair Francis <alistair23@...il.com>
Cc:     bhelgaas@...gle.com, linux-pci@...r.kernel.org,
        Jonathan.Cameron@...wei.com, alex.williamson@...hat.com,
        christian.koenig@....com, kch@...dia.com,
        gregkh@...uxfoundation.org, logang@...tatee.com,
        linux-kernel@...r.kernel.org,
        Alistair Francis <alistair.francis@....com>
Subject: Re: [PATCH v3] PCI/DOE: Expose the DOE protocols via sysfs

On Wed, Aug 09, 2023 at 07:28:51PM -0400, Alistair Francis wrote:
> --- a/drivers/pci/pci-sysfs.c
> +++ b/drivers/pci/pci-sysfs.c
> @@ -1226,6 +1227,12 @@ static int pci_create_resource_files(struct pci_dev *pdev)
>  	int i;
>  	int retval;
>  
> +#ifdef CONFIG_PCI_DOE
> +	retval = doe_sysfs_init(pdev);
> +	if (retval)
> +		return retval;
> +#endif
> +

The preferred way to expose PCI sysfs attributes nowadays is to add them
to pci_dev_attr_groups[] and use the ->is_visible callback to check
whether they're applicable to a particular pci_dev.  The alternative
via pci_create_resource_files() has race conditions which I think
still haven't been fixed. Bjorn recommended the ->is_visible approach
in response to the most recent attempt to fix the race:

https://lore.kernel.org/linux-pci/20230427161458.GA249886@bhelgaas/

To avoid (most of) the #ifdefs, you may want to consider adding a
doe-sysfs.c file like I've done for cma in this commit:

https://github.com/l1k/linux/commit/b057e2fb0ee0

Thanks,

Lukas