linux-kernel - Re: [PATCH 6/6 v3] regmap: Incorporate the regcache core into regmap

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Date:	Thu, 15 Sep 2011 23:57:05 +0100
From:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
To:	Lars-Peter Clausen <lars@...afoo.de>
Cc:	Dimitris Papastamos <dp@...nsource.wolfsonmicro.com>,
	linux-kernel@...r.kernel.org, Liam Girdwood <lrg@...com>,
	Graeme Gregory <gg@...mlogic.co.uk>,
	Samuel Oritz <sameo@...ux.intel.com>
Subject: Re: [PATCH 6/6 v3] regmap: Incorporate the regcache core into regmap

On Thu, Sep 15, 2011 at 05:19:32PM +0200, Lars-Peter Clausen wrote:

> > +	if (!map->cache_bypass) {
> > +		ret = regcache_write(map, reg, val);
> > +		if (ret < 0) {
> > +			mutex_unlock(&map->lock);
> > +			return ret;
> > +		}
> > +		if (map->cache_only) {
> > +			mutex_unlock(&map->lock);
> > +			return 0;
> > +		}
> > +	}

> Would it make sense to move this into _regmap_write ? In that case the code
> wouldn't have to be duplicated in regmap_update_bits and as a bonus it wouldn't
> have to deal with the mutex either.

That does seem sensible, yes.

> > +	if (!map->cache_bypass) {
> > +		ret = regcache_read(map, reg, val);
> > +		if (!ret) {
> > +			mutex_unlock(&map->lock);
> > +			return 0;
> > +		}

> So in case regmap_readable is not true for this register regcache_read will
> return -EIO and we'll fallback to an uncached read. This doesn't make sense in
> my opinion. Or what are the except semantics regmap_readable supposed to be?

It's a bit interesting but falling back to asking the hardware is
probably the right thing to do for cases where you're doing things like
using unspecified registers to activate undocumented features - the
register isn't really documented as being there and may do odd things
but if the device manufacturer gives you an approved sequence then you
can probably use it safely.
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