Re: [PATCH] drm/bridge: Avoid uninitialized variable warning

[Dan Carpenter <dan.carpenter@oracle.com>]

On Tue, Jun 28, 2022 at 09:26:09AM +0200, Boris Brezillon wrote:
> On Tue, 28 Jun 2022 09:59:51 +0300
> Dan Carpenter <dan.carpenter@oracle.com> wrote:
> 
> > This works, but technically it uses "num_in_bus_fmts" before it has been
> > initialized so it leads to static checker warnings and probably KMEMsan
> > warnings at run time.  Reverse the checks so it checks for failure first
> > and then check for unsupported formats next.
> > 
> > Fixes: f32df58acc68 ("drm/bridge: Add the necessary bits to support bus format negotiation")
> > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> > ---
> >  drivers/gpu/drm/drm_bridge.c | 12 ++++++------
> >  1 file changed, 6 insertions(+), 6 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
> > index e275b4ca344b..00cbde654472 100644
> > --- a/drivers/gpu/drm/drm_bridge.c
> > +++ b/drivers/gpu/drm/drm_bridge.c
> > @@ -897,10 +897,10 @@ static int select_bus_fmt_recursive(struct drm_bridge *first_bridge,
> >  							conn_state,
> >  							out_bus_fmt,
> >  							&num_in_bus_fmts);
> > -	if (!num_in_bus_fmts)
> > -		return -ENOTSUPP;
> > -	else if (!in_bus_fmts)
> > +	if (!in_bus_fmts)
> >  		return -ENOMEM;
> > +	else if (!num_in_bus_fmts)
> > +		return -ENOTSUPP;
> 
> Well, it changes the error we return when num_in_bus_fmts = 0
> && in_bus_fmts == NULL which is not an ENOMEM situation, so I'd rather
> initialize num_{in,out}_bus_fmts to 0 here.
> 

I can do that but there is no real consistency in how
->atomic_get_input_bus_fmts() functions are implemented.  Some set
*num_input_fmts = 0; before the kmalloc() and then reset it to
*num_input_fmts = 1; if the allocation succeeds.  Some just set it to
*num_input_fmts = 1 at the start.

This bug only affects the imx code like:
imx8qm_ldb_bridge_atomic_get_input_bus_fmts()
imx8qxp_pixel_link_bridge_atomic_get_input_bus_fmts

Anyway, it's not a problem to resend.

regards,
dan carpenter