linux-kernel - Re: Simple MFD driver example

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Date:	Wed, 18 Dec 2013 11:59:13 +0000
From:	Lee Jones <lee.jones@...aro.org>
To:	Laszlo Papp <lpapp@....org>
Cc:	sameo@...ux.intel.com, LKML <linux-kernel@...r.kernel.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Guenter Roeck <linux@...ck-us.net>
Subject: Re: Simple MFD driver example

On Wed, 18 Dec 2013, Laszlo Papp wrote:

> On Wed, Dec 18, 2013 at 11:34 AM, Lee Jones <lee.jones@...aro.org> wrote:
> >> >> What you eventually see in hwmon is only a subset of all the features
> >> >> the IC provides. You may want to read this thread:
> >> >> https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg536509.html
> >> >
> >> > Okay, so the best thing to do is send out the entire patch-set at
> >> > once, CC'ing each of the maintainers on every patch so we can all see
> >> > how this thing fits together.
> >>
> >> Well, I am not even sure currently where to head with the MFD bits and
> >> its children subdevices currently....
> >>
> >> I would appreciate any direction. Yesterday, I was told on IRC, I
> >> would need to switch from i2c to platform drivers for the hwmon and
> >> gpio parts, but looking at some existing mfd driver code and their
> >> children drivers, I do not see it like that.
> >>
> >> I have already sent out the gpio driver yesterday which works fine on
> >> its own: http://www.spinics.net/lists/kernel/msg1655805.html
> >
> > This is going to need a lot of work.
> >
> > Did you run the patch through `./scripts/checkpatch.pl` before
> > submitting?
> 
> Of course, there has been zero errors and warnings. Eventually, I even
> ran the Lindent. Actual feedback is welcome for sure.

I barely have enough time to review my own subsystem, let alone
others. Linus will do a great job in this regard.

> >> Could you please guide me into the right direction what I need to
> >> change once we have standalone drivers, and they should be glued
> >> together? I thought adding an abstraction with the mfd layer would be
> >> sufficient, but apparently, that is not enough.
> >>
> >> Practically speaking, I am confused since if I needed to change the
> >> existing drivers, that means I could potentially break the interface
> >> for the existing users if the drivers stop working on their own, but
> >> then again, I am such a newbie that I would greatly appreciate some
> >> pointers.
> >
> > The MFD subsystem is quite simple to use. I'm taken aback that this is
> > your major stumbling block. Read though the mfd_add_device(s)() calls
> > to see what it expects. The rest is childs play.
> 
> Yeah, I have taken, but that does not still explain the consistency I
> mentioned above. Some children do not conform the "platform" driver
> suggestion I was told.
> 
> Also, what about the actual MFD code submitted? Anything to modify in
> there? Could you please comment on that, or is the direction of it
> good enough for me to submit it as a real patch at this stage?

Submit them all as I requested before and we will do a proper review.

Copy and pasting patches into conversation emails isn't the correct
method to use.

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