Re: [PATCH v1 2/2] usb: gadget: composite: Draw 100mA current if not configured

[Prashanth K]

On 23-02-23 01:03 pm, Jack Pham wrote:
> Hi Prashanth,
>
> On Thu, Feb 23, 2023 at 10:48:30AM +0530, Prashanth K wrote:
> > Currently we don't change the current value if device isn't in
> > configured state. But the battery charging specification says,
> > the device can draw upto 100mA of current if its in unconfigured
>
> Here you say spec says "up to" (BTW you have a typo) 100mA...
Will fix it in v2
> > state. Hence add a Vbus_draw work in composite_resume to draw
> > 100mA if the device isn't configured.
>
> But here and in the patch you are calling the function to draw exactly
> 100mA.  Consider the possibility that a gadget could be configured to
> draw less current than that or not anything at all, we should make sure
> to honor that as an absolute maximum.
That's right
> > Signed-off-by: Prashanth K <quic_prashk@xxxxxxxxxxx>
> > ---
> >   drivers/usb/gadget/composite.c | 2 ++
> >   1 file changed, 2 insertions(+)
> >
> > diff --git a/drivers/usb/gadget/composite.c b/drivers/usb/gadget/composite.c
> > index fa7dd6c..147d278 100644
> > --- a/drivers/usb/gadget/composite.c
> > +++ b/drivers/usb/gadget/composite.c
> > @@ -2531,6 +2531,8 @@ void composite_resume(struct usb_gadget *gadget)
> >   			usb_gadget_clear_selfpowered(gadget);
> >   
> >   		usb_gadget_vbus_draw(gadget, maxpower);
> > +	} else {
> > +		usb_gadget_vbus_draw(gadget, 100);
>
> Similar to the configured case, maybe you can perform a min()
> calculation against either or both the config->MaxPower or
> CONFIG_USB_GADGET_VBUS_DRAW.
Thanks for the suggestion, will update it in v2 patch
> Thanks,
> Jack