PCI: Add managed partial-BAR request and map infrastructure

The pcim_iomap_devres table tracks entire-BAR mappings, so we can't use it
to build a managed version of pci_iomap_range(), which maps partial BARs.

Add struct pcim_addr_devres, which can track request and mapping of both
entire BARs and partial BARs.

Add the following internal devres functions based on struct
pcim_addr_devres:

  pcim_iomap_region()               # request & map entire BAR
  pcim_iounmap_region()             # unmap & release entire BAR
  pcim_request_region()             # request entire BAR
  pcim_release_region()             # release entire BAR
  pcim_request_all_regions()        # request all entire BARs
  pcim_release_all_regions()        # release all entire BARs

Rework the following public interfaces using the new infrastructure
listed above:

  pcim_iomap()                      # map partial BAR
  pcim_iounmap()                    # unmap partial BAR
  pcim_iomap_regions()              # request & map specified BARs
  pcim_iomap_regions_request_all()  # request all BARs, map specified BARs
  pcim_iounmap_regions()            # unmap & release specified BARs

Link: https://lore.kernel.org/r/20240613115032.29098-4-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/pci.c

@@ -3883,6 +3883,17 @@ void pci_release_region(struct pci_dev *pdev, int bar)
 		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);
@@ -3927,6 +3938,17 @@ 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;

drivers/pci/pci.h

@@ -826,6 +826,11 @@ 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;
 };