linux-kernel - Re: [spi-devel-general] adding bits_per_word to struct spi_board_info to mirror struct spi

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Message-Id: <200704250813.30999.david-b@pacbell.net>
Date:	Wed, 25 Apr 2007 08:13:30 -0700
From:	David Brownell <david-b@...bell.net>
To:	spi-devel-general@...ts.sourceforge.net
Cc:	"Mike Frysinger" <vapier.adi@...il.com>,
	"Wu, Bryan" <Bryan.Wu@...log.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [spi-devel-general] adding bits_per_word to struct spi_board_info to mirror struct spi_device

On Wednesday 25 April 2007, Mike Frysinger wrote:
> the spi_device structure has a bits_per_word so that you can change
> the value on a per-device setting, yet the spi_board_info structure
> does not ... this means that the bus-specific structure has to have a
> bits_per_word member which the spi bus driver will copy into the spi
> device bits_per_word member

Actually that's more likely a driver-specific characteristic than
something related to board wiring/configuration ... a characteristic
of the particular protocol requests being made.  That's why for
example bits_per_word has a per-transfer override, and drivers are
able to call spi_setup(spi).


> is there something obvious i'm missing ?  seems to me that if the
> generic spi framework respects bits_per_word on a per-spi device
> basis, then it should be exposed in the generic info structure so that
> the setting can be tracked in the boards file ...

The initial driver set didn't need it, that's all.  ISTR someone
else pointed out this quirk, but never provided a patch to resolve
the issue.

- Dave
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