linux-kernel - Re: [PATCH] regmap: Add support for 12/20 register formatting

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Date:   Thu, 17 Sep 2020 08:31:54 +0200
From:   Ricardo Ribalda Delgado <ribalda@...nel.org>
To:     Mark Brown <broonie@...nel.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] regmap: Add support for 12/20 register formatting

Hi Mark




On Wed, Sep 16, 2020 at 6:29 PM Mark Brown <broonie@...nel.org> wrote:
>
> On Wed, Sep 16, 2020 at 06:05:52PM +0200, Ricardo Ribalda wrote:
> > From: Ricardo Ribalda <ricardo@...alda.com>
> >
> > Devices such as the AD5628 require 32 bits of data divided in 12 bits
> > for dummy, command and address, and 20 for data and dummy.
>
> What exactly is the format you're trying to describe here?  It sounds
> like there's two blocks of padding in here (I'm assuing that's what
> dummy means) but what's the exact arrangement here and what are the
> commands?  It sounds like this might not work ideally with things like
> the cache code (if it makes things seems sparser than they are) and
> might not be obvious to someone looking at the datsheet.

The format is

XXXXCCCCAAAADDDDDDDDDDDDDDDDXXXX

Where X is dont care, C is command, A is address and D is data bits. I
am using the following config successfully:

static const struct regmap_config config_dac = {
.reg_bits = 12,
.val_bits = 20,
.max_register = 0xff,
};

Shall I add this to the commit message? I want to send a V2 anyway,
because I screwed up the identity (ribalda.com instead of kernel.org)

Thanks