[PATCH v8 07/12] xhci: Add option to get next extended capability in list by passing id = 0

[Heikki Krogerus]

From: Mathias Nyman <mathias.nyman@xxxxxxxxxxxxxxx>

Modify xhci_find_next_ext_cap(base, offset, id) to return the next
capability offset if 0 is passed for id. Otherwise it will behave as
previously and return the offset of the next capability with matching id

capability id 0 is not used by xHCI (reserved)

This is useful when we want to loop through all capabilities.

Signed-off-by: Mathias Nyman <mathias.nyman@xxxxxxxxxxxxxxx>
Reviewed-by: Andy Shevchenko <andy.shevchenko@xxxxxxxxx>
Signed-off-by: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
---
Changes in v4:
-Add Andy's Reviewed-by

Changes in v2:
-Added Heikki's Reviewed-by
---
 drivers/usb/host/xhci-ext-caps.h | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/host/xhci-ext-caps.h b/drivers/usb/host/xhci-ext-caps.h
index bf7316e130d3..631e7cc62604 100644
--- a/drivers/usb/host/xhci-ext-caps.h
+++ b/drivers/usb/host/xhci-ext-caps.h
@@ -84,7 +84,8 @@
  * @base	PCI MMIO registers base address.
  * @start	address at which to start looking, (0 or HCC_PARAMS to start at
  *		beginning of list)
- * @id		Extended capability ID to search for.
+ * @id		Extended capability ID to search for, or 0 for the next
+ *		capability
  *
  * Returns the offset of the next matching extended capability structure.
  * Some capabilities can occur several times, e.g., the XHCI_EXT_CAPS_PROTOCOL,
@@ -110,7 +111,7 @@ static inline int xhci_find_next_ext_cap(void __iomem *base, u32 start, int id)
 		val = readl(base + offset);
 		if (val == ~0)
 			return 0;
-		if (XHCI_EXT_CAPS_ID(val) == id && offset != start)
+		if (offset != start && (id == 0 || XHCI_EXT_CAPS_ID(val) == id))
 			return offset;
 
 		next = XHCI_EXT_CAPS_NEXT(val);
-- 
2.16.1