From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ozlabs.org (ozlabs.org [203.10.76.45]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "mx.ozlabs.org", Issuer "CA Cert Signing Authority" (verified OK)) by bilbo.ozlabs.org (Postfix) with ESMTPS id C43B3B709B for ; Sat, 6 Jun 2009 23:43:09 +1000 (EST) From: Frank Mori Hess To: Greg KH 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 References: <20090605182625.24093.7808.sendpatchset@elm3a191.beaverton.ibm.com> <1244261806.31984.36.camel@pasglop> <20090606055103.GA9446@kroah.com> In-Reply-To: <20090606055103.GA9446@kroah.com> MIME-Version: 1.0 Content-Type: multipart/signed; boundary="nextPart1334805.Ii2zXVS4iC"; protocol="application/pgp-signature"; micalg=pgp-sha1 Message-Id: <200906060936.22322.fmhess@speakeasy.net> Cc: sachinp@linux.vnet.ibm.com, Frank Mori Hess , sfr@canb.auug.org.au, linux-kernel@vger.kernel.org, Linuxppc-dev@ozlabs.org, Ian Abbott , linux-next@vger.kernel.org, paulus@samba.org, Geert.Uytterhoeven@sonycom.com, geert@linux-m68k.org, subrata@linux.vnet.ibm.com, David Miller Reply-To: fmhess@users.sourceforge.net List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , --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--