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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