Re: [PATCH v2 07/10] PCI/DOE: Create mailboxes on device enumeration

[Jonathan Cameron <Jonathan.Cameron@Huawei.com>]

On Mon, 23 Jan 2023 11:17:00 +0100
Lukas Wunner <lukas@wunner.de> wrote:

> Currently a DOE instance cannot be shared by multiple drivers because
> each driver creates its own pci_doe_mb struct for a given DOE instance.
> For the same reason a DOE instance cannot be shared between the PCI core
> and a driver.
> 
> Overcome this limitation by creating mailboxes in the PCI core on device
> enumeration.  Provide a pci_find_doe_mailbox() API call to allow drivers
> to get a pci_doe_mb for a given (pci_dev, vendor, protocol) triple.
> 
> On device removal, tear down mailboxes in two steps:
> 
> In pci_stop_dev(), before the driver is unbound, stop ongoing DOE
> exchanges and prevent new ones from being scheduled.  This ensures that
> a hot-removed device doesn't needlessly wait for a running exchange to
> time out.

Ah. I didn't have to go far to find answer to my earlier query!  This
needs to be two step - hence the split in the previous patch.

> 
> In pci_destroy_dev(), after the driver is unbound, free the mailboxes
> and their internal data structures.
> 
> Tested-by: Ira Weiny <ira.weiny@intel.com>
> Signed-off-by: Lukas Wunner <lukas@wunner.de>

Very nice.  One comment on a possible future need inline.

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>


> +/**
> + * pci_find_doe_mailbox() - Find Data Object Exchange mailbox
> + *
> + * @pdev: PCI device
> + * @vendor: Vendor ID
> + * @type: Data Object Type
> + *
> + * Find first DOE mailbox of a PCI device which supports the given protocol.
> + *
> + * RETURNS: Pointer to the DOE mailbox or NULL if none was found.
> + */
> +struct pci_doe_mb *pci_find_doe_mailbox(struct pci_dev *pdev, u16 vendor,
> +					u8 type)

This is good for now.  We may want eventually to be slightly
more flexible and allow for a 'find instance X of a DOE that supports Y'.
Can solve that when we need it though.

> +{
> +	struct pci_doe_mb *doe_mb;
> +	unsigned long index;
> +
> +	xa_for_each(&pdev->doe_mbs, index, doe_mb)
> +		if (pci_doe_supports_prot(doe_mb, vendor, type))
> +			return doe_mb;
> +
> +	return NULL;
> +}
> +EXPORT_SYMBOL_GPL(pci_find_doe_mailbox);