On Fri, Jan 27, 2012 at 04:19:15PM +0200, Felipe Balbi wrote:
> __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 ?
Sure, this looks like a good idea. I'll queue it for 3.4 after testing
it.
Sarah
>
> 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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