From: Frank Mori Hess <fmhess@speakeasy.net>
To: Greg KH <greg@kroah.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Ian Abbott <abbotti@mev.co.uk>,
Frank Mori Hess <fmhess@users.sourceforge.net>,
David Miller <davem@davemloft.net>,
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
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 [thread overview]
Message-ID: <200906060936.22322.fmhess@speakeasy.net> (raw)
In-Reply-To: <20090606055103.GA9446@kroah.com>
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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.
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next prev parent reply other threads:[~2009-06-06 13:36 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-06-05 18:26 [BUILD FAILURE 01/04] Next June 04:PPC64 randconfig [drivers/staging/comedi/drivers.o] Subrata Modak
2009-06-05 18:26 ` Greg KH
2009-06-05 23:31 ` Benjamin Herrenschmidt
2009-06-05 23:32 ` Benjamin Herrenschmidt
2009-06-06 0:56 ` David Miller
2009-06-06 4:16 ` Benjamin Herrenschmidt
2009-06-06 5:51 ` Greg KH
2009-06-06 13:36 ` Frank Mori Hess [this message]
2009-06-07 14:36 ` Subrata Modak
2009-06-09 3:50 ` Benjamin Herrenschmidt
2009-06-09 18:34 ` Subrata Modak
2009-06-09 18:54 ` Geert Uytterhoeven
2009-06-09 22:34 ` Benjamin Herrenschmidt
-- strict thread matches above, loose matches on Subject: below --
2009-06-04 13:31 Subrata Modak
2009-06-04 18:07 ` Greg KH
2009-06-04 20:40 ` Geert Uytterhoeven
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