linux-kernel - Re: [PATCH 11/20] regmap: _regmap_raw_read: Add handling of busses without bus->read()

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Message-ID: <20150812123412.GG19600@pengutronix.de>
Date:	Wed, 12 Aug 2015 14:34:12 +0200
From:	Markus Pargmann <mpa@...gutronix.de>
To:	Mark Brown <broonie@...nel.org>
Cc:	Jonathan Cameron <jic23@...nel.org>,
	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
	linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, kernel@...gutronix.de
Subject: Re: [PATCH 11/20] regmap: _regmap_raw_read: Add handling of busses
 without bus->read()

On Wed, Aug 12, 2015 at 12:27:07PM +0100, Mark Brown wrote:
> On Wed, Aug 12, 2015 at 12:12:36PM +0200, Markus Pargmann wrote:
> 
> > +	/*
> > +	 * There are busses that do not have a read function as it is optional.
> > +	 * Use their reg_read function instead if the requested number of bytes
> > +	 * is correct.
> > +	 */
> > +	if (!map->bus->read) {
> > +		/*
> > +		 * bus_reg_read() does not support reading values that are not
> > +		 * exactly the size of format.val_bytes
> > +		 */
> > +		if (val_len != map->format.val_bytes)
> > +			return -EINVAL;
> > +		return _regmap_bus_reg_read(map, reg, val);
> > +	}
> 
> No, this makes no sense - if the device doesn't have a read operation
> then it doesn't support a raw data stream and hence can't support raw
> access sensibly.  Callers that want to access a lot of registers at once
> without knowing what the wire format for the device is should be using
> the bulk or multi interfaces.

Yes okay. Then I will reduce this patch to the following and put it
into regmap_read() instead?
	if (!map->bus->read) {
		return -EINVAL;

Is -EINVAL the right thing to return or would you prefer -ENOTSUPP?

Thanks,

Markus

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