Re: [PATCH] drm/bridge: ti-sn65dsi86: fix a ternary type promotion bug

Robert Foss
2021-05-18T13:29:19Z

Since it fixes drm-misc-next, applied it there instead.

On Tue, 18 May 2021 at 15:20, Robert Foss <robert.foss@linaro.org> wrote:
>
> Hey Dan,
>
> Thanks for submitting this.
>
> On Tue, 18 May 2021 at 11:20, Dan Carpenter <dan.carpenter@oracle.com> wrote:
> >
> > The ti_sn_aux_transfer() function returns ssize_t (signed long). It's
> > supposed to return negative error codes or the number of bytes
> > transferred. The "ret" variable is int and the "len" variable is
> > unsigned int.
> >
> > The problem is that with a ternary like this, the negative int is first
> > type promoted to unsigned int to match "len" at this point it is a high
> > positive value. Then when it is type promoted to ssize_t (s64) it
> > remains a high positive value instead of sign extending and becoming a
> > negative again.
> >
> > Fix this by removing the ternary.
> >
> > Fixes: b137406d9679 ("drm/bridge: ti-sn65dsi86: If refclk, DP AUX can happen w/out pre-enable")
> > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> > ---
> > drivers/gpu/drm/bridge/ti-sn65dsi86.c | 4 +++-
> > 1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi86.c b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
> > index bb0a0e1c6341..45a2969afb2b 100644
> > --- a/drivers/gpu/drm/bridge/ti-sn65dsi86.c
> > +++ b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
> > @@ -1042,7 +1042,9 @@ static ssize_t ti_sn_aux_transfer(struct drm_dp_aux *aux,
> > pm_runtime_mark_last_busy(pdata->dev);
> > pm_runtime_put_autosuspend(pdata->dev);
> >
> > - return ret ? ret : len;
> > + if (ret)
> > + return ret;
> > + return len;
> > }
> >
>
> Reviewed-by: Robert Foss <robert.foss@linaro.org>
>
> Applying to drm-misc-fixes.