[PATCH] PCI: add pci_find_next_capability()

Some devices have more than one capability of the same type.  For
example, the PCI header for the PathScale InfiniPath looks like:

	04:01.0 InfiniBand: Unknown device 1fc1:000d (rev 02)
		Subsystem: Unknown device 1fc1:000d
		Flags: bus master, fast devsel, latency 0, IRQ 193
		Memory at fea00000 (64-bit, non-prefetchable) [size=2M]
		Capabilities: [c0] HyperTransport: Slave or Primary Interface
		Capabilities: [f8] HyperTransport: Interrupt Discovery and Configuration

There are _two_ HyperTransport capabilities, and the PathScale driver
wants to look at both of them.

The current pci_find_capability() API doesn't work for this, since it
only allows us to get to the first capability of a given type.  The
patch below introduces a new pci_find_next_capability(), which can be
used in a loop like

	for (pos = pci_find_capability(pdev, <ID>);
	     pos;
	     pos = pci_find_next_capability(pdev, pos, <ID>)) {
		/* ... */
	}

Signed-off-by: Roland Dreier <rolandd@cisco.com>
Signed-off-by: Matthew Wilcox <matthew@wil.cx>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

2 files changed, 34 insertions, 14 deletions

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index e74d75843047..8e287a828d5d 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -63,11 +63,38 @@ pci_max_busnr(void)
         return max;
 }
 
+static int __pci_find_next_cap(struct pci_bus *bus, unsigned int devfn, u8 pos, int cap)
+{
+        u8 id;
+        int ttl = 48;
+
+        while (ttl--) {
+                pci_bus_read_config_byte(bus, devfn, pos, &pos);
+                if (pos < 0x40)
+                        break;
+                pos &= ~3;
+                pci_bus_read_config_byte(bus, devfn, pos + PCI_CAP_LIST_ID,
+                                         &id);
+                if (id == 0xff)
+                        break;
+                if (id == cap)
+                        return pos;
+                pos += PCI_CAP_LIST_NEXT;
+        }
+        return 0;
+}
+
+int pci_find_next_capability(struct pci_dev *dev, u8 pos, int cap)
+{
+        return __pci_find_next_cap(dev->bus, dev->devfn,
+                                   pos + PCI_CAP_LIST_NEXT, cap);
+}
+EXPORT_SYMBOL_GPL(pci_find_next_capability);
+
 static int __pci_bus_find_cap(struct pci_bus *bus, unsigned int devfn, u8 hdr_type, int cap)
 {
         u16 status;
-        u8 pos, id;
-        int ttl = 48;
+        u8 pos;
 
         pci_bus_read_config_word(bus, devfn, PCI_STATUS, &status);
         if (!(status & PCI_STATUS_CAP_LIST))
@@ -76,24 +103,15 @@ static int __pci_bus_find_cap(struct pci_bus *bus, unsigned int devfn, u8 hdr_ty
         switch (hdr_type) {
         case PCI_HEADER_TYPE_NORMAL:
         case PCI_HEADER_TYPE_BRIDGE:
-                pci_bus_read_config_byte(bus, devfn, PCI_CAPABILITY_LIST, &pos);
+                pos = PCI_CAPABILITY_LIST;
                 break;
         case PCI_HEADER_TYPE_CARDBUS:
-                pci_bus_read_config_byte(bus, devfn, PCI_CB_CAPABILITY_LIST, &pos);
+                pos = PCI_CB_CAPABILITY_LIST;
                 break;
         default:
                 return 0;
         }
-        while (ttl-- && pos >= 0x40) {
-                pos &= ~3;
-                pci_bus_read_config_byte(bus, devfn, pos + PCI_CAP_LIST_ID, &id);
-                if (id == 0xff)
-                        break;
-                if (id == cap)
-                        return pos;
-                pci_bus_read_config_byte(bus, devfn, pos + PCI_CAP_LIST_NEXT, &pos);
-        }
-        return 0;
+        return __pci_find_next_cap(bus, devfn, pos, cap);
 }
 
 /**
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 3596ac94ecff..7063241e34d9 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -338,6 +338,7 @@ struct pci_dev *pci_find_device (unsigned int vendor, unsigned int device, const
 struct pci_dev *pci_find_device_reverse (unsigned int vendor, unsigned int device, const struct pci_dev *from);
 struct pci_dev *pci_find_slot (unsigned int bus, unsigned int devfn);
 int pci_find_capability (struct pci_dev *dev, int cap);
+int pci_find_next_capability (struct pci_dev *dev, u8 pos, int cap);
 int pci_find_ext_capability (struct pci_dev *dev, int cap);
 struct pci_bus * pci_find_next_bus(const struct pci_bus *from);
 
@@ -550,6 +551,7 @@ static inline int pci_assign_resource(struct pci_dev *dev, int i) { return -EBUS
 static inline int pci_register_driver(struct pci_driver *drv) { return 0;}
 static inline void pci_unregister_driver(struct pci_driver *drv) { }
 static inline int pci_find_capability (struct pci_dev *dev, int cap) {return 0; }
+static inline int pci_find_next_capability (struct pci_dev *dev, u8 post, int cap) { return 0; }
 static inline int pci_find_ext_capability (struct pci_dev *dev, int cap) {return 0; }
 static inline const struct pci_device_id *pci_match_device(const struct pci_device_id *ids, const struct pci_dev *dev) { return NULL; }