From mboxrd@z Thu Jan 1 00:00:00 1970 From: Frank Mori Hess Subject: Re: [BUILD FAILURE 01/04] Next June 04:PPC64 randconfig [drivers/staging/comedi/drivers.o] Date: Sat, 6 Jun 2009 09:36:17 -0400 Message-ID: <200906060936.22322.fmhess@speakeasy.net> References: <20090605182625.24093.7808.sendpatchset@elm3a191.beaverton.ibm.com> <1244261806.31984.36.camel@pasglop> <20090606055103.GA9446@kroah.com> Reply-To: fmhess@users.sourceforge.net Mime-Version: 1.0 Content-Type: multipart/signed; boundary="nextPart1334805.Ii2zXVS4iC"; protocol="application/pgp-signature"; micalg=pgp-sha1 Content-Transfer-Encoding: 7bit Return-path: Received: from mail8.sea5.speakeasy.net ([69.17.117.10]:58937 "EHLO mail8.sea5.speakeasy.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751663AbZFFNgW (ORCPT ); Sat, 6 Jun 2009 09:36:22 -0400 In-Reply-To: <20090606055103.GA9446@kroah.com> Sender: linux-next-owner@vger.kernel.org List-ID: To: Greg KH Cc: Benjamin Herrenschmidt , Ian Abbott , Frank Mori Hess , David Miller , subrata@linux.vnet.ibm.com, 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 --nextPart1334805.Ii2zXVS4iC Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Content-Disposition: inline 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=20 board (for example when producing an analog output waveform). Reads and=20 writes to the device files read/write to the circular buffer, plus a few=20 drivers do dma directly to/from it. I personally don't have a problem=20 with requiring drivers to have their own dma buffers and making them copy=20 data between their private dma buffers and the main circular buffer. I=20 guess the original design wanted to support zero-copy dma. --nextPart1334805.Ii2zXVS4iC Content-Type: application/pgp-signature; name=signature.asc Content-Description: This is a digitally signed message part. -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (GNU/Linux) iD8DBQBKKnDT5vihyNWuA4URAm5TAJ9uya8bxVj7LuYrvxrcOgiaZyFqNACg1QmH YUnOo4ea6+gFgDXBWgPrrd4= =vopu -----END PGP SIGNATURE----- --nextPart1334805.Ii2zXVS4iC--