linux-kernel - Re: [PATCH v16 0/4] Introduce usb charger framework to deal with the usb gadget power negotation

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Message-ID: <20160914180214.GI27974@sirena.org.uk>
Date:   Wed, 14 Sep 2016 19:02:14 +0100
From:   Mark Brown <broonie@...nel.org>
To:     NeilBrown <neilb@...e.com>
Cc:     Baolin Wang <baolin.wang@...aro.org>,
        Felipe Balbi <balbi@...nel.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        Sebastian Reichel <sre@...nel.org>,
        Dmitry Eremin-Solenikov <dbaryshkov@...il.com>,
        David Woodhouse <dwmw2@...radead.org>, robh@...nel.org,
        Jun Li <jun.li@....com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Ruslan Bilovol <ruslan.bilovol@...il.com>,
        Peter Chen <peter.chen@...escale.com>,
        Alan Stern <stern@...land.harvard.edu>, r.baldyga@...sung.com,
        grygorii.strashko@...com,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        Lee Jones <lee.jones@...aro.org>,
        Charles Keepax <ckeepax@...nsource.wolfsonmicro.com>,
        patches@...nsource.wolfsonmicro.com,
        Linux PM list <linux-pm@...r.kernel.org>,
        USB <linux-usb@...r.kernel.org>,
        device-mainlining@...ts.linuxfoundation.org,
        LKML <linux-kernel@...r.kernel.org>,
        "Bird, Timothy" <Tim.Bird@...sony.com>
Subject: Re: [PATCH v16 0/4] Introduce usb charger framework to deal with the
 usb gadget power negotation

On Wed, Sep 14, 2016 at 07:50:00PM +0200, NeilBrown wrote:
> On Wed, Sep 14 2016, Mark Brown wrote:

> Ah.... my mistake, sorry.
> When earlier you said:

> >                                                                 It's a
> > current limiter intended to sit in line with the USB power lines to

> I assumed that all it did was limit the current to number given.
> If it also limits the current to ensure that voltage doesn't drop
> unduly, then I agree with your assertion that it just needs to be told
> the upper limit.

Oh, I see the gap here - the USB specific bit is only a current limiter
but it works in concert with other bits of the system that try to stop
the voltage from whatever supply is in use from dropping and can't be
used independently of them.  That's why I wasn't clear in what I said!

> I hope you'll agree that other drivers might need to know the lower
> limit, so reporting both to all drivers is sensible.

Yes, absolutely.

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