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.
Alan Stern
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