Re: [PATCH v3 10/13] media: v4l2-fwnode: Update V4L2_FWNODE_CSI2_MAX_DATA_LANES to 8

[Sowjanya Komatineni]

On 12/8/20 11:59 AM, Sakari Ailus wrote:
> Hi Hans,
>
> On Mon, Dec 07, 2020 at 11:47:38AM +0100, Hans Verkuil wrote:
> > On 03/12/2020 19:59, Sowjanya Komatineni wrote:
> > > Some CSI2 receivers support 8 data lanes.
> > >
> > > So, this patch updates CSI2 maximum data lanes to be 8.
> > >
> > > Signed-off-by: Sowjanya Komatineni <skomatineni@xxxxxxxxxx>
> > > ---
> > >   drivers/media/platform/ti-vpe/cal-camerarx.c | 2 +-
> > >   include/media/v4l2-fwnode.h                  | 2 +-
> > >   2 files changed, 2 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/media/platform/ti-vpe/cal-camerarx.c b/drivers/media/platform/ti-vpe/cal-camerarx.c
> > > index 806cbf1..47e2143 100644
> > > --- a/drivers/media/platform/ti-vpe/cal-camerarx.c
> > > +++ b/drivers/media/platform/ti-vpe/cal-camerarx.c
> > > @@ -534,7 +534,7 @@ static int cal_camerarx_parse_dt(struct cal_camerarx *phy)
> > >   {
> > >   	struct v4l2_fwnode_endpoint *endpoint = &phy->endpoint;
> > >   	struct device_node *ep_node;
> > > -	char data_lanes[V4L2_FWNODE_CSI2_MAX_DATA_LANES * 2];
> > > +	char data_lanes[V4L2_FWNODE_CSI2_MAX_DATA_LANES];
> > >   	unsigned int i;
> > >   	int ret;
> > >   
> > I'm not so sure about this change: it relies on the implicit knowledge that
> > this cal driver can handle only 4 lanes max, so that doubling
> > V4L2_FWNODE_CSI2_MAX_DATA_LANES is the same as the old 'V4L2_FWNODE_CSI2_MAX_DATA_LANES * 2'.
> >
> > I think we should either keep the existing code (which means data_lanes
> > is now larger than needed, so stack usage increases by 8 bytes), or perhaps
> > create a new define for this driver like CAL_MAX_DATA_LANES and use that.
> >
> > In my opinion the original code should just be kept, but I've CC-ed Laurent
> > on this to hear what he thinks.
> I further looked at the code there and it does *depend* on a particular
> value of V4L2_FWNODE_CSI2_MAX_DATA_LANES. That needs to be fixed. This part
> can (or should) be dropped from the patch though.
Thanks Sakari and Hans.

OK. Will drop updating cal-camerarx.c from this patch in next version.