From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755235Ab3KEPKQ (ORCPT ); Tue, 5 Nov 2013 10:10:16 -0500 Received: from mga14.intel.com ([143.182.124.37]:51117 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754482Ab3KEPKO (ORCPT ); Tue, 5 Nov 2013 10:10:14 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.93,535,1378882800"; d="scan'208";a="384928470" Message-ID: <527909EF.3020806@linux.intel.com> Date: Tue, 05 Nov 2013 07:08:31 -0800 From: David Cohen User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20131005 Icedove/17.0.9 MIME-Version: 1.0 To: Alan Stern CC: balbi@ti.com, gregkh@linuxfoundation.org, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 2/4] usb: gadget: add quirk_ep_out_aligned_size field to struct usb_gadget References: In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/05/2013 06:50 AM, Alan Stern wrote: > On Mon, 4 Nov 2013, David Cohen wrote: > >> Due to USB controllers may have different restrictions, usb gadget layer >> needs to provide a generic way to inform gadget functions to complain >> with non-standard requirements. >> >> This patch adds 'quirk_ep_out_aligned_size' field to struct usb_gadget >> to inform when controller's epout requires buffer size to be aligned to >> MaxPacketSize. A helper is also provided to align buffer size when >> necessary. >> >> Signed-off-by: David Cohen >> --- >> include/linux/usb/gadget.h | 19 +++++++++++++++++++ >> 1 file changed, 19 insertions(+) >> >> diff --git a/include/linux/usb/gadget.h b/include/linux/usb/gadget.h >> index 23b3bfd0a842..260d972489bd 100644 >> --- a/include/linux/usb/gadget.h >> +++ b/include/linux/usb/gadget.h >> @@ -442,6 +442,22 @@ static inline void usb_ep_fifo_flush(struct usb_ep *ep) >> } >> >> >> +static inline size_t usb_ep_align_maxpacketsize(struct usb_ep *ep, size_t len) >> +{ >> + int aligned; >> + >> + if (ep->desc->bmAttributes & USB_ENDPOINT_XFER_INT) >> + /* >> + * Interrupt eps don't need max packet size to be power of 2, >> + * so can't use cheap IS_ALIGNED() macro. >> + */ >> + aligned = !(len % ep->desc->wMaxPacketSize); >> + else >> + aligned = IS_ALIGNED(len, ep->desc->wMaxPacketSize); > > This isn't on a hot path, and I suspect that the extra "if" will > require nearly as much time as you save by not doing the division. You > might as well always use the % operation. Perhaps if I use unlikely() on 'if' condition instead? Anyway I'll double check the costs of if + IS_ALIGNED vs modulo. Br, David