PCI: Add managed pcim_request_region()

These existing functions:

  pci_request_region()
  pci_request_selected_regions()
  pci_request_selected_regions_exclusive()

are "hybrid" functions built on __pci_request_region() and are managed if
pcim_enable_device() has been called, but unmanaged otherwise.

Add these new functions:

  pcim_request_region()
  pcim_request_region_exclusive()

These are *always* managed and use the new pcim_addr_devres tracking
infrastructure instead of find_pci_dr() and struct pci_devres.region_mask.

Implement the hybrid functions using the new "pure" functions and remove
struct pci_devres.region_mask, which is no longer needed.

Link: https://lore.kernel.org/r/20240613115032.29098-6-pstanner@redhat.com
Signed-off-by: Philipp Stanner <pstanner@redhat.com>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
[bhelgaas: commit log]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

drivers/pci/devres.c

@@ -24,18 +24,16 @@
  *
  *    Consequently, in the new API, region requests performed by the pcim_
  *    functions are automatically cleaned up through the devres callback
- *    pcim_addr_resource_release(), while requests performed by
+ *    pcim_addr_resource_release().
- *    pcim_enable_device() + pci_*region*() are automatically cleaned up
- *    through the for-loop in pcim_release().
  *
- * TODO 1:
+ *    Users of pcim_enable_device() + pci_*region*() are redirected in
+ *    pci.c to the managed functions here in this file. This isn't exactly
+ *    perfect, but the only alternative way would be to port ALL drivers
+ *    using said combination to pcim_ functions.
+ *
+ * TODO:
  * Remove the legacy table entirely once all calls to pcim_iomap_table() in
  * the kernel have been removed.
- *
- * TODO 2:
- * Port everyone calling pcim_enable_device() + pci_*region*() to using the
- * pcim_ functions. Then, remove all devres functionality from pci_*region*()
- * functions and remove the associated cleanups described above in point #2.
  */
 
 /*
@@ -402,22 +400,6 @@ static void pcim_release(struct device *gendev, void *res)
 {
 	struct pci_dev *dev = to_pci_dev(gendev);
 	struct pci_devres *this = res;
-	int i;
-
-	/*
-	 * This is legacy code.
-	 *
-	 * All regions requested by a pcim_ function do get released through
-	 * pcim_addr_resource_release(). Thanks to the hybrid nature of the pci_
-	 * region-request functions, this for-loop has to release the regions
-	 * if they have been requested by such a function.
-	 *
-	 * TODO: Remove this once all users of pcim_enable_device() PLUS
-	 * pci-region-request-functions have been ported to pcim_ functions.
-	 */
-	for (i = 0; i < DEVICE_COUNT_RESOURCE; i++)
-		if (mask_contains_bar(this->region_mask, i))
-			pci_release_region(dev, i);
 
 	if (this->mwi)
 		pci_clear_mwi(dev);
@@ -826,11 +808,29 @@ static int _pcim_request_region(struct pci_dev *pdev, int bar, const char *name,
  * The region will automatically be released on driver detach. If desired,
  * release manually only with pcim_release_region().
  */
-static int pcim_request_region(struct pci_dev *pdev, int bar, const char *name)
+int pcim_request_region(struct pci_dev *pdev, int bar, const char *name)
 {
 	return _pcim_request_region(pdev, bar, name, 0);
 }
 
+/**
+ * pcim_request_region_exclusive - Request a PCI BAR exclusively
+ * @pdev: PCI device to requestion region for
+ * @bar: Index of BAR to request
+ * @name: Name associated with the request
+ *
+ * Returns: 0 on success, a negative error code on failure.
+ *
+ * Request region specified by @bar exclusively.
+ *
+ * The region will automatically be released on driver detach. If desired,
+ * release manually only with pcim_release_region().
+ */
+int pcim_request_region_exclusive(struct pci_dev *pdev, int bar, const char *name)
+{
+	return _pcim_request_region(pdev, bar, name, IORESOURCE_EXCLUSIVE);
+}
+
 /**
  * pcim_release_region - Release a PCI BAR
  * @pdev: PCI device to operate on
@@ -839,7 +839,7 @@ static int pcim_request_region(struct pci_dev *pdev, int bar, const char *name)
  * Release a region manually that was previously requested by
  * pcim_request_region().
  */
-static void pcim_release_region(struct pci_dev *pdev, int bar)
+void pcim_release_region(struct pci_dev *pdev, int bar)
 {
 	struct pcim_addr_devres res_searched;
 

drivers/pci/pci.c

@@ -3872,7 +3872,15 @@ EXPORT_SYMBOL(pci_enable_atomic_ops_to_root);
  */
 void pci_release_region(struct pci_dev *pdev, int bar)
 {
-	struct pci_devres *dr;
+	/*
+	 * This is done for backwards compatibility, because the old PCI devres
+	 * API had a mode in which the function became managed if it had been
+	 * enabled with pcim_enable_device() instead of pci_enable_device().
+	 */
+	if (pci_is_managed(pdev)) {
+		pcim_release_region(pdev, bar);
+		return;
+	}
 
 	if (pci_resource_len(pdev, bar) == 0)
 		return;
@@ -3882,21 +3890,6 @@ void pci_release_region(struct pci_dev *pdev, int bar)
 	else if (pci_resource_flags(pdev, bar) & IORESOURCE_MEM)
 		release_mem_region(pci_resource_start(pdev, bar),
 				pci_resource_len(pdev, bar));
-
-	/*
-	 * This devres utility makes this function sometimes managed
-	 * (when pcim_enable_device() has been called before).
-	 *
-	 * This is bad because it conflicts with the pcim_ functions being
-	 * exclusively responsible for managed PCI. Its "sometimes yes,
-	 * sometimes no" nature can cause bugs.
-	 *
-	 * TODO: Remove this once all users that use pcim_enable_device() PLUS
-	 * a region request function have been ported to using pcim_ functions.
-	 */
-	dr = find_pci_dr(pdev);
-	if (dr)
-		dr->region_mask &= ~(1 << bar);
 }
 EXPORT_SYMBOL(pci_release_region);
 
@@ -3922,7 +3915,12 @@ EXPORT_SYMBOL(pci_release_region);
 static int __pci_request_region(struct pci_dev *pdev, int bar,
 				const char *res_name, int exclusive)
 {
-	struct pci_devres *dr;
+	if (pci_is_managed(pdev)) {
+		if (exclusive == IORESOURCE_EXCLUSIVE)
+			return pcim_request_region_exclusive(pdev, bar, res_name);
+
+		return pcim_request_region(pdev, bar, res_name);
+	}
 
 	if (pci_resource_len(pdev, bar) == 0)
 		return 0;
@@ -3938,21 +3936,6 @@ static int __pci_request_region(struct pci_dev *pdev, int bar,
 			goto err_out;
 	}
 
-	/*
-	 * This devres utility makes this function sometimes managed
-	 * (when pcim_enable_device() has been called before).
-	 *
-	 * This is bad because it conflicts with the pcim_ functions being
-	 * exclusively responsible for managed pci. Its "sometimes yes,
-	 * sometimes no" nature can cause bugs.
-	 *
-	 * TODO: Remove this once all users that use pcim_enable_device() PLUS
-	 * a region request function have been ported to using pcim_ functions.
-	 */
-	dr = find_pci_dr(pdev);
-	if (dr)
-		dr->region_mask |= 1 << bar;
-
 	return 0;
 
 err_out:

drivers/pci/pci.h

@@ -826,16 +826,15 @@ struct pci_devres {
 	unsigned int orig_intx:1;
 	unsigned int restore_intx:1;
 	unsigned int mwi:1;
-
-	/*
-	 * TODO: remove the region_mask once everyone calling
-	 * pcim_enable_device() + pci_*region*() is ported to pcim_ functions.
-	 */
-	u32 region_mask;
 };
 
 struct pci_devres *find_pci_dr(struct pci_dev *pdev);
 
+int pcim_request_region(struct pci_dev *pdev, int bar, const char *name);
+int pcim_request_region_exclusive(struct pci_dev *pdev, int bar,
+				  const char *name);
+void pcim_release_region(struct pci_dev *pdev, int bar);
+
 /*
  * Config Address for PCI Configuration Mechanism #1
  *