[PATCH 6.6 1335/1674] PCI: Introduce PCI_SLOT_PLACEHOLDER constant for slot_nr placeholder value

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

6.6-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Farhan Ali <alifm@linux.ibm.com>

[ Upstream commit c243e6c470c4695965cc8287767925bc1d9a7867 ]

Introduce a constant for placeholder value and update the kerneldoc for
pci_create_slot() to reference PCI_SLOT_PLACEHOLDER instead of -1
throughout. No functional change.

Suggested-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Farhan Ali <alifm@linux.ibm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Tyrel Datwyler <tyreld@linux.ibm.com>
Cc: linuxppc-dev@lists.ozlabs.org
Link: https://patch.msgid.link/20260805165518.794-2-alifm@linux.ibm.com
Stable-dep-of: dcc5bec09e23 ("PCI: Allow per function PCI slots to fix slot reset on s390")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/pci/hotplug/pnv_php.c     |  2 +-
 drivers/pci/hotplug/rpaphp_slot.c |  2 +-
 drivers/pci/slot.c                | 30 +++++++++++++++++-------------
 include/linux/pci.h               | 13 ++++++++++++-
 4 files changed, 31 insertions(+), 16 deletions(-)

diff --git a/drivers/pci/hotplug/pnv_php.c b/drivers/pci/hotplug/pnv_php.c
index ec7828ad66617..2bd2b7599d1c4 100644
--- a/drivers/pci/hotplug/pnv_php.c
+++ b/drivers/pci/hotplug/pnv_php.c
@@ -799,7 +799,7 @@ static struct pnv_php_slot *pnv_php_alloc_slot(struct device_node *dn)
 	if (dn->child && PCI_DN(dn->child))
 		php_slot->slot_no = PCI_SLOT(PCI_DN(dn->child)->devfn);
 	else
-		php_slot->slot_no = -1;   /* Placeholder slot */
+		php_slot->slot_no = PCI_SLOT_PLACEHOLDER;   /* Placeholder slot */
 
 	kref_init(&php_slot->kref);
 	php_slot->state	                = PNV_PHP_STATE_INITIALIZED;
diff --git a/drivers/pci/hotplug/rpaphp_slot.c b/drivers/pci/hotplug/rpaphp_slot.c
index 779eab12e9810..ac8c512190df4 100644
--- a/drivers/pci/hotplug/rpaphp_slot.c
+++ b/drivers/pci/hotplug/rpaphp_slot.c
@@ -85,7 +85,7 @@ int rpaphp_register_slot(struct slot *slot)
 	struct device_node *child;
 	u32 my_index;
 	int retval;
-	int slotno = -1;
+	int slotno = PCI_SLOT_PLACEHOLDER;
 
 	dbg("%s registering slot:path[%pOF] index[%x], name[%s] pdomain[%x] type[%d]\n",
 		__func__, slot->dn, slot->index, slot->name,
diff --git a/drivers/pci/slot.c b/drivers/pci/slot.c
index ed645c7a4e4b4..3a233b4a13136 100644
--- a/drivers/pci/slot.c
+++ b/drivers/pci/slot.c
@@ -38,7 +38,7 @@ static const struct sysfs_ops pci_slot_sysfs_ops = {
 
 static ssize_t address_read_file(struct pci_slot *slot, char *buf)
 {
-	if (slot->number == 0xff)
+	if (slot->number == PCI_SLOT_PLACEHOLDER)
 		return sysfs_emit(buf, "%04x:%02x\n",
 				  pci_domain_nr(slot->bus),
 				  slot->bus->number);
@@ -74,7 +74,8 @@ static void pci_slot_release(struct kobject *kobj)
 
 	down_read(&pci_bus_sem);
 	list_for_each_entry(dev, &slot->bus->devices, bus_list)
-		if (PCI_SLOT(dev->devfn) == slot->number)
+		if (slot->number == PCI_SLOT_ALL_DEVICES ||
+		    PCI_SLOT(dev->devfn) == slot->number)
 			dev->slot = NULL;
 	up_read(&pci_bus_sem);
 
@@ -167,7 +168,8 @@ void pci_dev_assign_slot(struct pci_dev *dev)
 
 	mutex_lock(&pci_slot_mutex);
 	list_for_each_entry(slot, &dev->bus->slots, list)
-		if (PCI_SLOT(dev->devfn) == slot->number)
+		if (slot->number == PCI_SLOT_ALL_DEVICES ||
+		    PCI_SLOT(dev->devfn) == slot->number)
 			dev->slot = slot;
 	mutex_unlock(&pci_slot_mutex);
 }
@@ -189,7 +191,7 @@ static struct pci_slot *get_slot(struct pci_bus *parent, int slot_nr)
 /**
  * pci_create_slot - create or increment refcount for physical PCI slot
  * @parent: struct pci_bus of parent bridge
- * @slot_nr: PCI_SLOT(pci_dev->devfn) or -1 for placeholder
+ * @slot_nr: PCI_SLOT(pci_dev->devfn) or PCI_SLOT_PLACEHOLDER for placeholder
  * @name: user visible string presented in /sys/bus/pci/slots/<name>
  * @hotplug: set if caller is hotplug driver, NULL otherwise
  *
@@ -214,15 +216,16 @@ static struct pci_slot *get_slot(struct pci_bus *parent, int slot_nr)
  * In most cases, @pci_bus, @slot_nr will be sufficient to uniquely identify
  * a slot. There is one notable exception - pSeries (rpaphp), where the
  * @slot_nr cannot be determined until a device is actually inserted into
- * the slot. In this scenario, the caller may pass -1 for @slot_nr.
+ * the slot. In this scenario, the caller may pass PCI_SLOT_PLACEHOLDER for @slot_nr.
  *
  * The following semantics are imposed when the caller passes @slot_nr ==
- * -1. First, we no longer check for an existing %struct pci_slot, as there
- * may be many slots with @slot_nr of -1.  The other change in semantics is
- * user-visible, which is the 'address' parameter presented in sysfs will
- * consist solely of a dddd:bb tuple, where dddd is the PCI domain of the
- * %struct pci_bus and bb is the bus number. In other words, the devfn of
- * the 'placeholder' slot will not be displayed.
+ * PCI_SLOT_PLACEHOLDER. First, we no longer check for an existing %struct
+ * pci_slot, as there may be many slots with @slot_nr of
+ * PCI_SLOT_PLACEHOLDER. The other change in semantics is user-visible,
+ * which is the 'address' parameter presented in sysfs will consist solely
+ * of a dddd:bb tuple, where dddd is the PCI domain of the %struct pci_bus
+ * and bb is the bus number. In other words, the devfn of the 'placeholder'
+ * slot will not be displayed.
  */
 struct pci_slot *pci_create_slot(struct pci_bus *parent, int slot_nr,
 				 const char *name,
@@ -235,7 +238,7 @@ struct pci_slot *pci_create_slot(struct pci_bus *parent, int slot_nr,
 
 	mutex_lock(&pci_slot_mutex);
 
-	if (slot_nr == -1)
+	if (slot_nr == PCI_SLOT_PLACEHOLDER)
 		goto placeholder;
 
 	/*
@@ -287,7 +290,8 @@ struct pci_slot *pci_create_slot(struct pci_bus *parent, int slot_nr,
 
 	down_read(&pci_bus_sem);
 	list_for_each_entry(dev, &parent->devices, bus_list)
-		if (PCI_SLOT(dev->devfn) == slot_nr)
+		if (slot_nr == PCI_SLOT_ALL_DEVICES ||
+		    PCI_SLOT(dev->devfn) == slot_nr)
 			dev->slot = slot;
 	up_read(&pci_bus_sem);
 
diff --git a/include/linux/pci.h b/include/linux/pci.h
index bef23297fb801..b35a3fe9d46f5 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -72,12 +72,23 @@
 /* return bus from PCI devid = ((u16)bus_number) << 8) | devfn */
 #define PCI_BUS_NUM(x) (((x) >> 8) & 0xff)
 
+/*
+ * PCI_SLOT_ALL_DEVICES indicates a slot that covers all devices on the bus.
+ * Used for PCIe hotplug where the physical slot is the entire secondary bus,
+ * and, if ARI Forwarding is enabled, functions may appear to be on multiple
+ * devices.
+ */
+#define PCI_SLOT_ALL_DEVICES	0xfe
+
+/* Used to identify a slot as a placeholder */
+#define PCI_SLOT_PLACEHOLDER	0xff
+
 /* pci_slot represents a physical slot */
 struct pci_slot {
 	struct pci_bus		*bus;		/* Bus this slot is on */
 	struct list_head	list;		/* Node in list of slots */
 	struct hotplug_slot	*hotplug;	/* Hotplug info (move here) */
-	unsigned char		number;		/* PCI_SLOT(pci_dev->devfn) */
+	unsigned char		number;		/* Device nr, or PCI_SLOT_ALL_DEVICES */
 	struct kobject		kobj;
 };
 
-- 
2.53.0