linux-kernel - Re: [UPDATED v3][PATCH 5/7] regulator: sysfs ABI

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Date:	Sat, 08 Mar 2008 21:13:51 +0000
From:	Liam Girdwood <lg@...nsource.wolfsonmicro.com>
To:	David Brownell <david-b@...bell.net>
Cc:	linux-arm-kernel@...ts.arm.linux.org.uk,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [UPDATED v3][PATCH 5/7] regulator: sysfs ABI

On Fri, 2008-03-07 at 17:13 -0800, David Brownell wrote:
> On Thursday 06 March 2008, Liam Girdwood wrote:
> 
> > +What:		/sys/class/regulator/.../microvolts
> > +	...
> > +
> > +What:		/sys/class/regulator/.../microamps
> > +	...
> 
> Versus Documentation/hwmon/sysfs-interface which uses
> millivolts and milliamperes respectively.
> 
> Why not adopt the same convention?  (This applies to
> many attributes, not just these two.)
> 

I originally had milli but changed to micro to conform with
power_supply.h (as our PMIC uses this interface to export it input
supplies to userspace).

> 
> Also, I'm kind of curious what you've thought about
> power budgeting.  Example, a power supply ("regulator")
> may be able to supply a voltage within a given range,
> but only up to a maximum of 200 mA worth.
> 
> The model visible through these sysfs attributes seems to
> be an either/or thing ... either regulating voltage, or
> current, but not addressing the corresponding constraints
> on the other one.
> 

In general it's up to the system hardware designer to ensure each
regulator can supply all the consumers on the domain - hence we don't
have power budgeting in software atm. However, I don't think it would be
too difficult to add in the future.

I'll also add support for a regulator that will do both voltage and
current (although I'm not aware of any in the market atm).

> 
> > +               NOTE: this will return the string 'constraint not defined'
> 
> How about just "undefined" for all those min/max values?
> 

Agreed.

> 
> > +What:		/sys/class/regulator/.../requested_microamps
> > +	...
> 
> Ditto re "milli" vs "micro".  Also, "requested" seems a bit opaque.
> As a sum, maybe "total_mi{lli,cro}amps" would be more explanatory.
> 

Ok, total_ sounds good.

Liam

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