PCI: Add pci_rebar_get_max_size()

Add pci_rebar_get_max_size() to allow simplifying code that wants to know
the maximum possible size for a Resizable BAR.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Link: https://patch.msgid.link/20251113180053.27944-9-ilpo.jarvinen@linux.intel.com

Author: ij-intel

drivers/pci/rebar.c

@@ -5,6 +5,7 @@
 
 #include <linux/bits.h>
 #include <linux/bitfield.h>
+#include <linux/bitops.h>
 #include <linux/errno.h>
 #include <linux/export.h>
 #include <linux/ioport.h>
@@ -142,6 +143,28 @@ bool pci_rebar_size_supported(struct pci_dev *pdev, int bar, int size)
 }
 EXPORT_SYMBOL_GPL(pci_rebar_size_supported);
 
+/**
+ * pci_rebar_get_max_size - get the maximum supported size of a BAR
+ * @pdev: PCI device
+ * @bar: BAR to query
+ *
+ * Get the largest supported size of a resizable BAR as a size.
+ *
+ * Return: the encoded maximum BAR size as defined in the PCIe spec
+ *	   (0=1MB, 31=128TB), or %-NOENT on error.
+ */
+int pci_rebar_get_max_size(struct pci_dev *pdev, int bar)
+{
+	u32 sizes;
+
+	sizes = pci_rebar_get_possible_sizes(pdev, bar);
+	if (!sizes)
+		return -ENOENT;
+
+	return __fls(sizes);
+}
+EXPORT_SYMBOL_GPL(pci_rebar_get_max_size);
+
 /**
  * pci_rebar_get_current_size - get the current size of a Resizable BAR
  * @pdev: PCI device

include/linux/pci.h

@@ -1425,6 +1425,7 @@ int pci_rebar_bytes_to_size(u64 bytes);
 resource_size_t pci_rebar_size_to_bytes(int size);
 u32 pci_rebar_get_possible_sizes(struct pci_dev *pdev, int bar);
 bool pci_rebar_size_supported(struct pci_dev *pdev, int bar, int size);
+int pci_rebar_get_max_size(struct pci_dev *pdev, int bar);
 int __must_check pci_resize_resource(struct pci_dev *dev, int i, int size,
 				     int exclude_bars);