From: Niklas Schnelle <schnelle@linux.ibm.com>
Date: Tue, 28 Jun 2022 16:30:56 +0200
Subject: PCI: Clean up pci_scan_slot()
Git-commit: c3df83e01a96ca569d261bcdffa2fb858b1012fa
Patch-mainline: v6.0-rc1
References: jsc#PED-600
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>
Acked-by: Petr Tesarik <ptesarik@suse.com>
---
drivers/pci/probe.c | 38 +++++++++++++++++++-------------------
1 file changed, 19 insertions(+), 19 deletions(-)
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -2573,8 +2573,7 @@ struct pci_dev *pci_scan_single_device(s
}
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;
@@ -2582,24 +2581,26 @@ static unsigned int next_fn(struct pci_b
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)
@@ -2637,26 +2638,25 @@ static int only_one_child(struct pci_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)