linux-kernel - Re: [PATCH v4 01/17] mfd: madera: Add register definitions for Cirrus Logic Madera codecs

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Date:   Tue, 8 Aug 2017 12:03:19 +0100
From:   Lee Jones <lee.jones@...aro.org>
To:     Richard Fitzgerald <rf@...nsource.wolfsonmicro.com>
Cc:     broonie@...nel.org, linus.walleij@...aro.org, gnurou@...il.com,
        robh+dt@...nel.org, tglx@...utronix.de, jason@...edaemon.net,
        alsa-devel@...a-project.org, patches@...nsource.wolfsonmicro.com,
        linux-gpio@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 01/17] mfd: madera: Add register definitions for
 Cirrus Logic Madera codecs

On Fri, 28 Jul 2017, Richard Fitzgerald wrote:

> This patch adds a header file of register definitions for Cirrus
> Logic "Madera" class codecs. These codecs are all based off a common
> set of hardware IP so have a common register map (with a few minor
> device-to-device variations).
> 
> The registers.h file is tool-generated directly from the hardware design
> but has been manually stripped down to reduce size (full register
> map is >44000 lines). All names are kept the same as datasheet names
> so that they can be cross-referenced between source and datasheet without
> confusion.
> 
> The register map layout is kept fully-defined rather than factored into
> macros and/or block-indexing code. The major reasons for this are:
> 
>  - #1 is that it makes the source highly greppable, which is important.
>    "What does the driver do with register bits XYZ" or "Where does it use
>    register bits XYZ" are commonly types of questions. These can be quickly
>    answered by a grep. Squashing definitions into generator macros or block-
>    indexing code is a way of defeating grep.
> 
>  - most of the register definitions are used in tables, so a constant value
>    is required. Using generator macros make the table definition clunky and
>    obscure.
> 
>  - the code is clearer when it's there in the source exactly what register
>    and field it is using
> 
>  - it is easier to diff the register map of a new (unsupported) codec against
>    what is already supported and merge in differences
> 
>  - it makes the register map available in source for maintenance/debugging
>    instead of having to refer back to the datasheet for a register map
> 
> Signed-off-by: Richard Fitzgerald <rf@...nsource.wolfsonmicro.com>
> ---
> Changes since V3:
> - Manually stripped out a lot more stuff, defines we're not using right now
> - Added the explanation above to the commit message of why we define the
>   map effectively verbatim
> 
>  MAINTAINERS                          |   10 +
>  include/linux/mfd/madera/registers.h | 3987 ++++++++++++++++++++++++++++++++++
>  2 files changed, 3997 insertions(+)
>  create mode 100644 include/linux/mfd/madera/registers.h

For my own reference:
  Acked-for-MFD-by: Lee Jones <lee.jones@...aro.org>

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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