linux-kernel - Re: [PATCH 1/6] mfd: Add Delta TN48M CPLD driver

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Date:   Thu, 20 May 2021 07:49:29 +0100
From:   Lee Jones <lee.jones@...aro.org>
To:     Michael Walle <michael@...le.cc>
Cc:     Robert Marko <robert.marko@...tura.hr>, robh+dt@...nel.org,
        Linus Walleij <linus.walleij@...aro.org>,
        bgolaszewski@...libre.com, jdelvare@...e.com,
        Guenter Roeck <linux@...ck-us.net>, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-gpio@...r.kernel.org,
        linux-hwmon@...r.kernel.org, Luka Perkov <luka.perkov@...tura.hr>,
        jmp@...phyte.org, Paul Menzel <pmenzel@...gen.mpg.de>,
        Donald Buczek <buczek@...gen.mpg.de>
Subject: Re: [PATCH 1/6] mfd: Add Delta TN48M CPLD driver

On Wed, 19 May 2021, Michael Walle wrote:

> Hi,
> 
> Am 2021-05-19 13:53, schrieb Robert Marko:
> > On Thu, May 6, 2021 at 6:34 PM Michael Walle <michael@...le.cc> wrote:
> > > Am 2021-04-30 14:35, schrieb Robert Marko:
> > > > Delta TN48M switches have a Lattice CPLD that serves
> > > > multiple purposes including being a GPIO expander.
> > > > So lets add the MFD core driver for it.
> > > 
> > > Did you have a look at mfd/simple-mfd-i2c.c?
> > 
> > Yes, that was my first idea but we have a requirement to expose CPLD
> > information via debugfs as there are userspace applications using it.
> > And simple-mfd-i2c does not allow us to do so.
> 
> Mh, last time Lee wasn't very fond of having a driver that just populates
> sub-drivers while doing almost nothing itself. See
> https://lore.kernel.org/lkml/20200605065709.GD3714@dell/

Right.  I still feel that way.

> That being said, I'd also like to expose our CPLD version, but until now
> haven't found a good solution.

Why though?  Does S/W *need* it?

-- 
Lee Jones [李琼斯]
Senior Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
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