Re: [PATCH v2 2/6] media: nxp: imx8-isi: Add stream ID validation for crossbar routing

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

On Mon, Jul 20, 2026 at 10:11:21AM -0500, Frank Li wrote:
> On Mon, Jul 20, 2026 at 11:34:04AM +0800, Guoniu Zhou wrote:
> > Add validation to enforce hardware constraints that were previously
> > missing in the crossbar routing configuration:
> >
> > - SOURCE stream must be 0 (ISI pipes are hardcoded to stream 0)
> >
> > This check complements the existing memory input validation and ensures
> > that all routing configurations respect hardware limitations.
> >
> > Signed-off-by: Guoniu Zhou <guoniu.zhou@oss.nxp.com>
> > ---
> > Changes in v2:
> > - New patch split from v1 1/5: adds stream ID validation on top of
> >   for_each_active_route() fix (Frank Li)
> > - Remove incorrect sink_stream validation
> > ---
> >  drivers/media/platform/nxp/imx8-isi/imx8-isi-crossbar.c | 14 +++++++++++++-
> >  1 file changed, 13 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/media/platform/nxp/imx8-isi/imx8-isi-crossbar.c b/drivers/media/platform/nxp/imx8-isi/imx8-isi-crossbar.c
> > index 84871bceb31d..328d08a278ea 100644
> > --- a/drivers/media/platform/nxp/imx8-isi/imx8-isi-crossbar.c
> > +++ b/drivers/media/platform/nxp/imx8-isi/imx8-isi-crossbar.c
> > @@ -106,8 +106,20 @@ static int __mxc_isi_crossbar_set_routing(struct v4l2_subdev *sd,
> >  	if (ret)
> >  		return ret;
> >
> > -	/* The memory input can be routed to the first pipeline only. */
> > +	/*
> > +	 * Validate routes against hardware constraints:
> > +	 * - SOURCE stream must be 0 (pipes are hardcoded to stream 0)
> > +	 * - Memory input can only route to the first pipeline
> > +	 */
> >  	for_each_active_route(routing, route) {
> > +		if (route->source_stream != 0) {
> > +			dev_dbg(xbar->isi->dev,
> 
> it is one error, should be dev_err()?

As this is an error that can be triggered by userspace, we prefer
dev_dbg() to avoid giving unpriviledge userspace a way to flood the
kernel log.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

> > +				"route to pipe %u must use source_stream=0, got %u\n",
> > +				route->source_pad - xbar->num_sinks,
> > +				route->source_stream);
> > +			return -ENXIO;
> > +		}
> > +
> >  		if (route->sink_pad == xbar->num_sinks - 1 &&
> >  		    route->source_pad != xbar->num_sinks) {
> >  			dev_dbg(xbar->isi->dev,

-- 
Regards,

Laurent Pinchart