__ffs() can tell us which is the SEGMENT_SHIFT value
to be used. This will prevent problems when users are
too fast and don't pay attention to the need of fixing
the Shift after changing TRBS_PER_SEGMENT.
Signed-off-by: Felipe Balbi <balbi@xxxxxx>
---
*** COMPILE TESTED ONLY ***
Sarah, what do you think about this patch ?
drivers/usb/host/xhci.h | 5 +----
1 files changed, 1 insertions(+), 4 deletions(-)
diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h
index fb99c83..7bdfe5f 100644
--- a/drivers/usb/host/xhci.h
+++ b/drivers/usb/host/xhci.h
@@ -1223,10 +1223,7 @@ union xhci_trb {
/* Allow two commands + a link TRB, along with any reserved command TRBs */
#define MAX_RSVD_CMD_TRBS (TRBS_PER_SEGMENT - 3)
#define SEGMENT_SIZE (TRBS_PER_SEGMENT*16)
-/* SEGMENT_SHIFT should be log2(SEGMENT_SIZE).
- * Change this if you change TRBS_PER_SEGMENT!
- */
-#define SEGMENT_SHIFT 10
+#define SEGMENT_SHIFT (__ffs(SEGMENT_SIZE))
/* TRB buffer pointers can't cross 64KB boundaries */
#define TRB_MAX_BUFF_SHIFT 16
#define TRB_MAX_BUFF_SIZE (1 << TRB_MAX_BUFF_SHIFT)
--
1.7.8.2
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