On Wed, 2016-12-14 at 10:33 -0500, Alan Stern wrote:
> On Wed, 14 Dec 2016, Todd Brandt wrote:
>
> > add debugfs support for experimenting with USB timing delay
> > values on the fly. Values are read/written from debugfs at
> > /sys/kernel/debug/usb/timing.
> >
> > Signed-off-by: Todd Brandt <todd.e.brandt@xxxxxxxxxxxxxxx>
> > ---
> > v2 changes:
> > - moved the debug code from hub.c to usb.c
> > - use debugfs instead of /sys/kernel/usb
>
> ...
>
> > +static int usb_timing_show(struct seq_file *s, void *unused)
> > +{
> > + seq_printf(s, "tdrsmdn=%d\n", usb_timing.tdrsmdn);
> > + seq_printf(s, "trsmrcy=%d\n", usb_timing.trsmrcy);
> > + seq_printf(s, "trstrcy=%d\n", usb_timing.trstrcy);
> > + return 0;
> > +}
> > +
> > +static int usb_timing_open(struct inode *inode, struct file *file)
> > +{
> > + return single_open(file, usb_timing_show, inode->i_private);
> > +}
> > +
> > +static ssize_t usb_timing_write(struct file *file,
> > + const char __user *ubuf, size_t count, loff_t *ppos)
> > +{
> > + int val;
> > + char buf[32];
> > +
> > + if (copy_from_user(&buf, ubuf, min_t(size_t, sizeof(buf) - 1, count)))
> > + return -EFAULT;
> > +
> > + if (sscanf(buf, "tdrsmdn=%u", &val) == 1)
> > + usb_timing.tdrsmdn = max(val, USB_TIMING_TDRSMDN_MIN);
> > + else if (sscanf(buf, "trsmrcy=%u", &val) == 1)
> > + usb_timing.trsmrcy = max(val, USB_TIMING_TRSMRCY_MIN);
> > + else if (sscanf(buf, "trstrcy=%u", &val) == 1)
> > + usb_timing.trstrcy = max(val, USB_TIMING_TRSTRCY_MIN);
>
> Nit: Since the values in usb_timing are signed integers, and since val
> is a signed integer, why do the sscanf calls use %u rather than %d?
I just want the extra format checking for sscanf, it refuses negative
integers (I prefer an -EINVAL in the event of a negative time input
rather than a silient setting to VAL_MIN). I could declare val an
unsigned int, but then "max(" throws a warning about a type mismatch, so
I figured this was the simplest way to implement it without having to
use any casts.
>
> Alan Stern
>
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