Re: [PATCH 2/2] USB: resume timing debug

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On Sat, 2016-12-03 at 12:24 -0500, Alan Stern wrote:
> On Fri, 2 Dec 2016, Todd Brandt wrote:
> 
> > Add debug support for experimenting with USB timing delay
> > values on the fly. This provides a debug interface through
> > /sys/kernel/usb where a user can tweak the values. The code
> > enforces the spec minimums so that a user can't set them
> > too low.
> > 
> > Signed-off-by: Todd Brandt <todd.e.brandt@xxxxxxxxxxxxxxx>
> > ---
> >  drivers/usb/core/hub.c | 100 +++++++++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 100 insertions(+)
> > 
> > diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
> > index 43242e3..6dea6a7 100644
> > --- a/drivers/usb/core/hub.c
> > +++ b/drivers/usb/core/hub.c
> > @@ -5265,8 +5265,98 @@ static struct usb_driver hub_driver = {
> >  	.supports_autosuspend =	1,
> >  };
> >  
> > +static ssize_t tdrsmdn_show(struct kobject *kobj,
> > +		struct kobj_attribute *attr, char *buf)
> > +{
> > +	return sprintf(buf, "%d\n", usb_timing.tdrsmdn);
> > +}
> > +
> > +static ssize_t tdrsmdn_store(struct kobject *kobj,
> > +		struct kobj_attribute *attr, const char *buf, size_t count)
> > +{
> > +	int ret, val;
> > +
> > +	ret = kstrtoint(buf, 10, &val);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	if (val < 20)
> > +		usb_timing.tdrsmdn = 20;
> > +	else
> > +		usb_timing.tdrsmdn = val;
> 
> How about:
> 
> 		usb_timing.rdrsmdn = max(val, USB_TIMING_TDRSMDN_MIN);
> 
> and similarly for the others?  And how about making val unsigned?  A 
> negative timeout is pretty meaningless.

good call, I'll move it to debugfs and will stop using hardcoded values.

> 
> Alan Stern
> 


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