PCI: Add devres helpers for iomap table

The pcim_iomap_devres.table administrated by pcim_iomap_table() has its
entries set and unset at several places throughout devres.c using manual
iterations which are effectively code duplications.

Add pcim_add_mapping_to_legacy_table() and
pcim_remove_mapping_from_legacy_table() helper functions and use them where
possible.

Link: https://lore.kernel.org/r/20240613115032.29098-3-pstanner@redhat.com
Signed-off-by: Philipp Stanner <pstanner@redhat.com>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

drivers/pci/devres.c

@@ -297,6 +297,52 @@ void __iomem * const *pcim_iomap_table(struct pci_dev *pdev)
 }
 EXPORT_SYMBOL(pcim_iomap_table);
 
+/*
+ * Fill the legacy mapping-table, so that drivers using the old API can
+ * still get a BAR's mapping address through pcim_iomap_table().
+ */
+static int pcim_add_mapping_to_legacy_table(struct pci_dev *pdev,
+					    void __iomem *mapping, int bar)
+{
+	void __iomem **legacy_iomap_table;
+
+	if (bar >= PCI_STD_NUM_BARS)
+		return -EINVAL;
+
+	legacy_iomap_table = (void __iomem **)pcim_iomap_table(pdev);
+	if (!legacy_iomap_table)
+		return -ENOMEM;
+
+	/* The legacy mechanism doesn't allow for duplicate mappings. */
+	WARN_ON(legacy_iomap_table[bar]);
+
+	legacy_iomap_table[bar] = mapping;
+
+	return 0;
+}
+
+/*
+ * Remove a mapping. The table only contains whole-BAR mappings, so this will
+ * never interfere with ranged mappings.
+ */
+static void pcim_remove_mapping_from_legacy_table(struct pci_dev *pdev,
+						  void __iomem *addr)
+{
+	int bar;
+	void __iomem **legacy_iomap_table;
+
+	legacy_iomap_table = (void __iomem **)pcim_iomap_table(pdev);
+	if (!legacy_iomap_table)
+		return;
+
+	for (bar = 0; bar < PCI_STD_NUM_BARS; bar++) {
+		if (legacy_iomap_table[bar] == addr) {
+			legacy_iomap_table[bar] = NULL;
+			return;
+		}
+	}
+}
+
 /**
  * pcim_iomap - Managed pcim_iomap()
  * @pdev: PCI device to iomap for
@@ -308,16 +354,20 @@ EXPORT_SYMBOL(pcim_iomap_table);
  */
 void __iomem *pcim_iomap(struct pci_dev *pdev, int bar, unsigned long maxlen)
 {
-	void __iomem **tbl;
+	void __iomem *mapping;
 
-	BUG_ON(bar >= PCIM_IOMAP_MAX);
-
-	tbl = (void __iomem **)pcim_iomap_table(pdev);
-	if (!tbl || tbl[bar])	/* duplicate mappings not allowed */
+	mapping = pci_iomap(pdev, bar, maxlen);
+	if (!mapping)
 		return NULL;
 
-	tbl[bar] = pci_iomap(pdev, bar, maxlen);
-	return tbl[bar];
+	if (pcim_add_mapping_to_legacy_table(pdev, mapping, bar) != 0)
+		goto err_table;
+
+	return mapping;
+
+err_table:
+	pci_iounmap(pdev, mapping);
+	return NULL;
 }
 EXPORT_SYMBOL(pcim_iomap);
 
@@ -330,20 +380,9 @@ EXPORT_SYMBOL(pcim_iomap);
  */
 void pcim_iounmap(struct pci_dev *pdev, void __iomem *addr)
 {
-	void __iomem **tbl;
-	int i;
-
 	pci_iounmap(pdev, addr);
 
-	tbl = (void __iomem **)pcim_iomap_table(pdev);
-	BUG_ON(!tbl);
-
-	for (i = 0; i < PCIM_IOMAP_MAX; i++)
-		if (tbl[i] == addr) {
-			tbl[i] = NULL;
-			return;
-		}
-	WARN_ON(1);
+	pcim_remove_mapping_from_legacy_table(pdev, addr);
 }
 EXPORT_SYMBOL(pcim_iounmap);