From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752737AbaIXMAK (ORCPT ); Wed, 24 Sep 2014 08:00:10 -0400 Received: from mail-ig0-f182.google.com ([209.85.213.182]:37755 "EHLO mail-ig0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750767AbaIXMAI (ORCPT ); Wed, 24 Sep 2014 08:00:08 -0400 Date: Wed, 24 Sep 2014 13:00:02 +0100 From: Lee Jones To: Johan Hovold Cc: Octavian Purdila , linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org Subject: Re: [PATCH v2 1/2] mfd: viperboard: allocate I/O buffer separately Message-ID: <20140924120002.GA32069@lee--X1> References: <1411414759-7056-1-git-send-email-octavian.purdila@intel.com> <1411414759-7056-2-git-send-email-octavian.purdila@intel.com> <20140924101206.GD19999@lee--X1> <20140924102853.GA17019@localhost> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20140924102853.GA17019@localhost> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 24 Sep 2014, Johan Hovold wrote: > On Wed, Sep 24, 2014 at 11:12:06AM +0100, Lee Jones wrote: > > On Mon, 22 Sep 2014, Octavian Purdila wrote: > > > > > Currently the I/O buffer is allocated part of the device status > > > structure, potentially sharing the same cache line with other members > > > in this structure. > > > > > > Allocate the buffer separately, to avoid the I/O operations corrupting > > > the device status structure due to cache line sharing. > > > > > > Compiled tested only as I don't have access to hardware. > > > > > > Signed-off-by: Octavian Purdila > > > --- > > > drivers/mfd/viperboard.c | 8 ++++++++ > > > include/linux/mfd/viperboard.h | 2 +- > > > 2 files changed, 9 insertions(+), 1 deletion(-) > > > > > > diff --git a/drivers/mfd/viperboard.c b/drivers/mfd/viperboard.c > > > index e00f534..5f62f4e 100644 > > > --- a/drivers/mfd/viperboard.c > > > +++ b/drivers/mfd/viperboard.c > > > @@ -64,6 +64,12 @@ static int vprbrd_probe(struct usb_interface *interface, > > > return -ENOMEM; > > > } > > > > > > + vb->buf = kzalloc(sizeof(struct vprbrd_i2c_write_msg), GFP_KERNEL); > > > > Can you obtain the 'struct device' first then use managed resources > > (devm_*)? > > I think any devres conversion should be done in a follow-up patch and > not be included in the fix (e.g. in order to facilitate backporting). We > also don't want to mix allocation schemes. I agree, but equally I'm not keen on accepting this patch as I believe it could be done better. Please submit two patches, one converting to shared resources and this being the subsequent one, fixed up to do the right thing. -- Lee Jones Linaro STMicroelectronics Landing Team Lead Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog