Re: usb: common: usb-conn-gpio: Prevent bailing out if initial role is none

[Prashanth K]

On 25-07-23 09:04 pm, Greg Kroah-Hartman wrote:
> On Thu, Jul 06, 2023 at 03:40:58PM +0530, Prashanth K wrote:
> > Currently if we bootup a device without cable connected, then
> > usb-conn-gpio won't call set_role() since last_role is same as
> > current role. This happens because during probe last_role gets
> > initialised to zero.
> >
> > To avoid this, add a new flag initial_det in usb_conn_info,
> > which is used to prevent bailing out during init detection.
> >
> > Fixes: 4602f3bff266 ("usb: common: add USB GPIO based connection detection driver")
> > Signed-off-by: Prashanth K <quic_prashk@xxxxxxxxxxx>
> > ---
> >   drivers/usb/common/usb-conn-gpio.c | 6 +++++-
> >   1 file changed, 5 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/usb/common/usb-conn-gpio.c b/drivers/usb/common/usb-conn-gpio.c
> > index 766005d..46290ff 100644
> > --- a/drivers/usb/common/usb-conn-gpio.c
> > +++ b/drivers/usb/common/usb-conn-gpio.c
> > @@ -42,6 +42,7 @@ struct usb_conn_info {
> >   
> >   	struct power_supply_desc desc;
> >   	struct power_supply *charger;
> > +	bool initial_det;
>
> What does "initial_det" mean?  Please document this better.
Yea sure, will update that. It was supposed to mean initial_detection.
> >   };
> >   
> >   /*
> > @@ -86,11 +87,13 @@ static void usb_conn_detect_cable(struct work_struct *work)
> >   	dev_dbg(info->dev, "role %s -> %s, gpios: id %d, vbus %d\n",
> >   		usb_role_string(info->last_role), usb_role_string(role), id, vbus);
> >   
> > -	if (info->last_role == role) {
> > +	if (!info->initial_det && info->last_role == role) {
> >   		dev_warn(info->dev, "repeated role: %s\n", usb_role_string(role));
> >   		return;
> >   	}
> >   
> > +	info->initial_det = false;
> > +
> >   	if (info->last_role == USB_ROLE_HOST && info->vbus)
> >   		regulator_disable(info->vbus);
> >   
> > @@ -258,6 +261,7 @@ static int usb_conn_probe(struct platform_device *pdev)
> >   	device_set_wakeup_capable(&pdev->dev, true);
> >   
> >   	/* Perform initial detection */
> > +	info->initial_det = true;
>
> What is protecting this from changing right after you test for it?
>
> thanks,
>
> greg k-h

Hi Greg, this variable is only used/changed by usb_conn_detect_cable() 
which is called in next line. So the chance of it changing is none.
Basically this initial_det flag points if its initial detection or not.
If yes, then prevent bailing out in usb_conn_detect_cable(). Please let 
me know if your comment was regarding something else.

Regards,
Prashanth K