Commit c3df83e0 authored by Niklas Schnelle's avatar Niklas Schnelle Committed by Bjorn Helgaas
Browse files

PCI: Clean up pci_scan_slot() 

While determining the next PCI function is factored out of pci_scan_slot()
into next_fn(), the former still handles the first function as a special
case, which duplicates the code from the scan loop.

Furthermore the non-ARI branch of next_fn() is generally hard to understand
and especially the check for multifunction devices is hidden in the
handling of NULL devices for non-contiguous multifunction. It also signals
that no further functions need to be scanned by returning 0 via wraparound
and this is a valid function number.

Improve upon this by transforming the conditions in next_fn() to be easier
to understand.

By changing next_fn() to return -ENODEV instead of 0 when there is no next
function we can then handle the initial function inside the loop and
deduplicate the shared handling. This also makes it more explicit that only
function 0 must exist.

No functional change is intended.

Link: https://lore.kernel.org/r/20220628143100.3228092-2-schnelle@linux.ibm.com


Signed-off-by: default avatarNiklas Schnelle <schnelle@linux.ibm.com>
Signed-off-by: default avatarBjorn Helgaas <bhelgaas@google.com>
Cc: Jan Kiszka <jan.kiszka@siemens.com>
parent f2906aa8

drivers/pci/probe.c

+19 −19
Original line number Diff line number Diff line
@@ -2579,8 +2579,7 @@ struct pci_dev *pci_scan_single_device(struct pci_bus *bus, int devfn) 
}

EXPORT_SYMBOL(pci_scan_single_device);



static unsigned int next_fn(struct pci_bus *bus, struct pci_dev *dev,

			    unsigned int fn)

static int next_fn(struct pci_bus *bus, struct pci_dev *dev, int fn)

{

	int pos;

	u16 cap = 0;
@@ -2588,24 +2587,26 @@ static unsigned int next_fn(struct pci_bus *bus, struct pci_dev *dev, 


	if (pci_ari_enabled(bus)) {

		if (!dev)

			return 0;

			return -ENODEV;

		pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ARI);

		if (!pos)

			return 0;

			return -ENODEV;



		pci_read_config_word(dev, pos + PCI_ARI_CAP, &cap);

		next_fn = PCI_ARI_CAP_NFN(cap);

		if (next_fn <= fn)

			return 0;	/* protect against malformed list */

			return -ENODEV;	/* protect against malformed list */



		return next_fn;

	}



	/* dev may be NULL for non-contiguous multifunction devices */

	if (!dev || dev->multifunction)

		return (fn + 1) % 8;

	if (fn >= 7)

		return -ENODEV;

	/* only multifunction devices may have more functions */

	if (dev && !dev->multifunction)

		return -ENODEV;



	return 0;

	return fn + 1;

}



static int only_one_child(struct pci_bus *bus)
@@ -2643,26 +2644,25 @@ static int only_one_child(struct pci_bus *bus) 
 */

int pci_scan_slot(struct pci_bus *bus, int devfn)

{

	unsigned int fn, nr = 0;

	struct pci_dev *dev;

	int fn = 0, nr = 0;



	if (only_one_child(bus) && (devfn > 0))

		return 0; /* Already scanned the entire slot */



	dev = pci_scan_single_device(bus, devfn);

	if (!dev)

		return 0;

	if (!pci_dev_is_added(dev))

		nr++;



	for (fn = next_fn(bus, dev, 0); fn > 0; fn = next_fn(bus, dev, fn)) {

	do {

		dev = pci_scan_single_device(bus, devfn + fn);

		if (dev) {

			if (!pci_dev_is_added(dev))

				nr++;

			if (fn > 0)

				dev->multifunction = 1;

		} else if (fn == 0) {

			/* function 0 is required */

			break;

		}

	}

		fn = next_fn(bus, dev, fn);

	} while (fn >= 0);



	/* Only one slot has PCIe device */

	if (bus->self && nr)