linux-kernel - Re: [PATCH v3 2/2] usb: gadget: composite: Draw 100mA current if not configured

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Date:   Thu, 23 Feb 2023 20:10:22 +0000
From:   Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To:     Prashanth K <quic_prashk@...cinc.com>
CC:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        Jakob Koschel <jakobkoschel@...il.com>,
        Jó Ágila Bitsch <jgilab@...il.com>,
        Alan Stern <stern@...land.harvard.edu>,
        Pratham Pratap <quic_ppratap@...cinc.com>,
        Jack Pham <quic_jackp@...cinc.com>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 2/2] usb: gadget: composite: Draw 100mA current if not
 configured

On Thu, Feb 23, 2023, Prashanth K wrote:
> Currently we don't change the current value if device isn't in
> configured state. But the battery charging specification says,

Can you provide the spec section also?

> device can draw up to 100mA of current if its in unconfigured

Is this related to being self-powered?

> state. Hence add a Vbus_draw work in composite_resume to draw
> 100mA if the device isn't configured.
> 
> Signed-off-by: Prashanth K <quic_prashk@...cinc.com>
> ---
>  drivers/usb/gadget/composite.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/usb/gadget/composite.c b/drivers/usb/gadget/composite.c
> index 403563c..386140f 100644
> --- a/drivers/usb/gadget/composite.c
> +++ b/drivers/usb/gadget/composite.c
> @@ -2449,6 +2449,10 @@ void composite_resume(struct usb_gadget *gadget)
>  			usb_gadget_clear_selfpowered(gadget);
>  
>  		usb_gadget_vbus_draw(gadget, maxpower);
> +	} else {
> +		maxpower = CONFIG_USB_GADGET_VBUS_DRAW;
> +		maxpower = min(maxpower, 100U);
> +		usb_gadget_vbus_draw(gadget, maxpower);
>  	}
>  
>  	cdev->suspended = 0;
> -- 
> 2.7.4
> 

Thanks,
Thinh