Hi,
On Fri, Nov 21, 2014 at 06:24:44PM +0100, Robert Jarzmik wrote:
> Felipe Balbi <balbi@xxxxxx> writes:
>
> > On Sun, Nov 09, 2014 at 03:58:14PM +0100, Robert Jarzmik wrote:
> >> + if (!enabled) {
> >> + ret = regulator_enable(vbus_draw);
> >> + if (ret < 0)
> >> + return;
> >> + nop->vbus_draw_enabled = 1;
> >
> > do you really need this flag here ? How about:
> >
> > if (regulator_is_enabled(vbus_draw))
> > foo();
> Good question, I copy-pasted that code from gpio-vbus...
> Philipp, do you have an insight here ?
>
> >> + if (vbus) {
> >> + status = USB_EVENT_VBUS;
> >> + nop->phy.state = OTG_STATE_B_PERIPHERAL;
> >> + nop->phy.last_event = status;
> >> + usb_gadget_vbus_connect(otg->gadget);
> >> +
> >> + /* drawing a "unit load" is *always* OK, except for OTG */
> >> + nop_set_vbus_draw(nop, 100);
> >
> > right, we need to take into considering the Battery Charging
> > specification here, though. We might need to setup a timer for the
> > amount of time we can draw 100mA before device enumerates. If the times
> > expires we're only allowed to draw 8mA or 2mA, or something like that.
> >
> > The time gets cancelled as soon as we get enumerated.
> >
> > Another possibility would be to move this policy into userland, then
> > kernel only provides the interfaces.
> Ah ok.
> Do you know exactly what the spec is telling in here ?
I would have to go read the spec again to remember, but...
> Is it something such as :
> - upon vbus insertion, a UDC can draw 100mA during ??? ms
this is, IIRC, a rather long time. Something like 10 minutes or maybe
more. It falls into the dead battery provision.
> - if during ??? ms, the device is enumerated, it can continue drawing 100mA
either 100mA or bMaxPower from chosen configuration.
> - if not, it should not draw more than 8mA after ??? ms
yeah, something like that.
> Is this right ? I can add a timer I think, if the spec if that simple. Now if
> there are a lot of special cases then maybe it could be dropped to userland.
yeah, there quite a few special cases :-)
--
balbi
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