linux-kernel - Re: [PATCH v19 0/4] Introduce usb charger framework to deal with the usb gadget power negotation

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Date:   Wed, 29 Mar 2017 10:04:52 +1100
From:   NeilBrown <neilb@...e.com>
To:     Baolin Wang <baolin.wang@...aro.org>
Cc:     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>,
        grygorii.strashko@...com,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        Lee Jones <lee.jones@...aro.org>,
        Mark Brown <broonie@...nel.org>,
        John Stultz <john.stultz@...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>
Subject: Re: [PATCH v19 0/4] Introduce usb charger framework to deal with the usb gadget power negotation

On Tue, Mar 07 2017, Baolin Wang wrote:

> On 3 March 2017 at 10:23, NeilBrown <neilb@...e.com> wrote:
>
>>
>> I understand your reluctance to change drivers that you cannot test.
>> An alternative it do change all the
>>   atomic_notifier_call_chain(.*notifier,
>> calls that don't pass a pointer to vbus_draw to pass NULL, and to
>> declare the passing of NULL to be deprecated (so hopefully people won't
>> use it in new code).
>> Then any notification callback that expects a current can just ignore
>> calls where the pointer is NULL.
>
> I am afraid if it is enough to send out vbus draw information from USB
> phy driver, for example you will miss super speed (900mA), which need
> get the speed information from gadget driver.

When the gadget driver determines that 900mA is available, it calls
usb_phy_set_power() which calls the ->set_power() method on the usb_phy.
The usb_phy the uses the notifier to inform all interested parties
that 900mA is available.

NeilBrown

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