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

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Message-ID: <20150812112707.GY10748@sirena.org.uk>
Date:	Wed, 12 Aug 2015 12:27:07 +0100
From:	Mark Brown <broonie@...nel.org>
To:	Markus Pargmann <mpa@...gutronix.de>
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 12:12:36PM +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.

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