linux-kernel - Re: [PATCH 3/3] regcache: flat: Add valid bit to this cache type

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Date:   Mon, 8 Jan 2018 16:36:06 +0000
From:   Mark Brown <broonie@...nel.org>
To:     "Andrew F. Davis" <afd@...com>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] regcache: flat: Add valid bit to this cache type

On Mon, Jan 08, 2018 at 10:25:28AM -0600, Andrew F. Davis wrote:

> I can understand the need for a fast cache type, but without this change
> the implementation is simply wrong IMHO. Reading from a register that
> has not been read/written to should not just assume the default value is
> 0, it should first read and load the real initial value into the cache,
> just like other cache types do.

Users are supposed to ensure that the cache is fully initialized either
by supplying defaults or writing to all the registers.  Adding reads is
problematic since we'd suddenly start reading from hardware which might
not like it.

> Also, it looks like this cache type is used mostly in I2C devices
> (outside of sound/soc/, where in there, like you said MMIO devices are
> more common).

Sounds like a good thing to do an audit and contribute fixes for...

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