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PCI: Clean up pci_scan_slot()

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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: Niklas Schnelle <schnelle@linux.ibm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: Jan Kiszka <jan.kiszka@siemens.com>
This commit is contained in:
Niklas Schnelle 2022-06-28 16:30:56 +02:00 committed by Bjorn Helgaas
parent f2906aa863
commit c3df83e01a
1 changed files with 19 additions and 19 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

38
drivers/pci/probe.c
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@ -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++;
dev->multifunction = 1;
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)