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From: David Brownell <david-b@pacbell.net>
To: Mark Jackson <mpfj@mimc.co.uk>
Subject: Re: [PATCH] Add Dallas DS1390 RTC chip
Date: Fri, 17 Oct 2008 08:29:06 -0700
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Cc: Alessandro Zummo <alessandro.zummo@towertech.it>,
       rtc-linux@googlegroups.com, lkml <linux-kernel@vger.kernel.org>,
       spi-devel-general@lists.sourceforge.net
References: <48F452BE.2030901@mimc.co.uk> <20081014101703.1ded0259@i1501.lan.towertech.it> <48F8467C.5010902@mimc.co.uk>
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On Friday 17 October 2008, Mark Jackson wrote:
> >> +????/* Can tx_buf and rx_buf be equal? The doc in spi.h is not sure... */
> >> +????xfer.tx_buf = chip->tx_buf;
> >> +????xfer.rx_buf = chip->rx_buf;
> > 
> > ?you use the same buffer a few functions below. either
> > ?one way or the other. please investigate with the spi subsystem maintainer.
> 
> David,
> 
> Just to double check (as per Alessandro's suggestion), is this okay use of the 
> spi buffers ?

Yes.  That comment deserves to be updated.

SPI does bi-directional I/O, and the underlying controller
should be able to just replace the contents of a buffer
with a spi_transfer that uses the same rx and tx buffers.

- Dave
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