From mboxrd@z Thu Jan 1 00:00:00 1970 From: Subrata Modak Subject: Re: [BUILD FAILURE 01/04] Next June 04:PPC64 randconfig [drivers/staging/comedi/drivers.o] Date: Sun, 07 Jun 2009 20:06:45 +0530 Message-ID: <1244385405.5265.7.camel@subratamodak.linux.ibm.com> References: <20090605182625.24093.7808.sendpatchset@elm3a191.beaverton.ibm.com> <1244261806.31984.36.camel@pasglop> <20090606055103.GA9446@kroah.com> <200906060936.22322.fmhess@speakeasy.net> Reply-To: subrata@linux.vnet.ibm.com Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Return-path: Received: from e7.ny.us.ibm.com ([32.97.182.137]:60406 "EHLO e7.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750944AbZFGOgw (ORCPT ); Sun, 7 Jun 2009 10:36:52 -0400 In-Reply-To: <200906060936.22322.fmhess@speakeasy.net> Sender: linux-next-owner@vger.kernel.org List-ID: To: fmhess@users.sourceforge.net Cc: Greg KH , Benjamin Herrenschmidt , Ian Abbott , David Miller , sachinp@linux.vnet.ibm.com, sfr@canb.auug.org.au, linux-kernel@vger.kernel.org, Linuxppc-dev@ozlabs.org, linux-next@vger.kernel.org, paulus@samba.org, Geert.Uytterhoeven@sonycom.com, geert@linux-m68k.org On Sat, 2009-06-06 at 09:36 -0400, Frank Mori Hess wrote: > On Saturday 06 June 2009, Greg KH wrote: > > Frank and Ian, any thoughts about the vmap call in the > > comedi_buf_alloc() call? Why is it using PAGE_KERNEL_NOCACHE, and what > > is the prealloc_buf buffer used for? > > It is a circular buffer used to hold data streaming either to or from a > board (for example when producing an analog output waveform). Reads and > writes to the device files read/write to the circular buffer, plus a few > drivers do dma directly to/from it. I personally don't have a problem > with requiring drivers to have their own dma buffers and making them copy > data between their private dma buffers and the main circular buffer. I > guess the original design wanted to support zero-copy dma. Great to hear that. How about a patch that solves my build problem on PPC64(the problem seems to be existing for long) ? Regards-- Subrata >