linux-kernel - Re: [PATCH 09/20] regmap: _regmap_raw_write fix for busses without write()

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Date:	Fri, 14 Aug 2015 17:40:00 +0100
From:	Mark Brown <broonie@...nel.org>
To:	Markus Pargmann <mpa@...gutronix.de>
Cc:	linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
	Jonathan Cameron <jic23@...nel.org>, kernel@...gutronix.de,
	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 09/20] regmap: _regmap_raw_write fix for busses without
 write()

On Wed, Aug 12, 2015 at 03:05:18PM +0200, Markus Pargmann wrote:
> On Wed, Aug 12, 2015 at 01:34:06PM +0100, Mark Brown wrote:

> > > Yes right. On the other hand if bus->read() and bus->write() was not set
> > > in the init method (before this patch series) no formatting functions at
> > > all were assigned. So it was always ignored for bus->reg_read() and
> > > bus->reg_write()?!

> > I'm not sure what the "it" you're talking about here is, sorry.  There
> > are unsupported features in the API especially for cases that don't make
> > a huge amount of sense, the error handling isn't always complete.  It
> > sounds like you might be trying to support one of these nonsensical
> > cases - it's not obvious what raw I/O on a device where we don't know
> > the raw format of the device should mean or how anything could sensibly
> > use that.

> The bus and the regmap user are separate. So as a regmap user, I am not
> able to know if the bus the device is connected to actually supports raw
> reads/writes. At least it should not fail with a null pointer when using

You should generally have a pretty good idea simply by knowing which
device you're working with - unless you're writing generic code you know
which device you're working with and what it's capabilities are.  A
driver that doesn't know these things should never be trying to do raw
I/O, and a driver that is doing raw I/O clearly depends on having the
ability to get a bytestream to and from the device since that's what raw
I/O does.

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