On Mon 17 May 04:13 CDT 2021, Andy Shevchenko wrote:
> On Sun, May 16, 2021 at 6:47 AM Bjorn Andersson
> <bjorn.andersson@xxxxxxxxxx> wrote:
> >
> > In typec_mux_match() "nval" is assigned the number of elements in the
> > "svid" fwnode property, then the variable is used to store the success
> > of the read and finally attempts to loop between 0 and "success" - i.e.
> > not at all - and the code returns indicating that no match was found.
> >
> > Fix this by using a separate variable to track the success of the read,
> > to allow the loop to get a change to find a match.
> >
> > Fixes: 96a6d031ca99 ("usb: typec: mux: Find the muxes by also matching against the device node")
> > Signed-off-by: Bjorn Andersson <bjorn.andersson@xxxxxxxxxx>
> > ---
> > drivers/usb/typec/mux.c | 7 ++++---
> > 1 file changed, 4 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/usb/typec/mux.c b/drivers/usb/typec/mux.c
> > index 9da22ae3006c..8514bec7e1b8 100644
> > --- a/drivers/usb/typec/mux.c
> > +++ b/drivers/usb/typec/mux.c
> > @@ -191,6 +191,7 @@ static void *typec_mux_match(struct fwnode_handle *fwnode, const char *id,
> > bool match;
> > int nval;
> > u16 *val;
> > + int ret;
> > int i;
> >
> > /*
> > @@ -218,10 +219,10 @@ static void *typec_mux_match(struct fwnode_handle *fwnode, const char *id,
> > if (!val)
> > return ERR_PTR(-ENOMEM);
> >
> > - nval = fwnode_property_read_u16_array(fwnode, "svid", val, nval);
> > - if (nval < 0) {
> > + ret = fwnode_property_read_u16_array(fwnode, "svid", val, nval);
> > + if (ret < 0) {
> > kfree(val);
> > - return ERR_PTR(nval);
> > + return ERR_PTR(ret);
> > }
>
> This changes the behaviour of the original code, i.e. nval can be
> still positive but less than we got from previous call. Some fwnode
> backends in some cases potentially can _successfully_ read less than
> asked.
>
> Perhaps
>
> nval = ret;
>
> or drop the patch.
>
Per the kerneldoc of fwnode_property_read_u16_array:
* Return: number of values if @val was %NULL,
* %0 if the property was found (success),
@val is not NULL, as we just checked for that, so the function will
always return 0 on success.
I don't see anything indicating that the number of elements can be
different from what fwnode_property_count_u16() returned.
Regards,
Bjorn
> > for (i = 0; i < nval; i++) {
>
>
> --
> With Best Regards,
> Andy Shevchenko
