Re: [PATCH] [media] smiapp: provide g_skip_top_lines method in sensor ops

From: Ivaylo Dimitrov
Date: Mon Apr 18 2016 - 02:28:03 EST


On 18.04.2016 00:44, Sakari Ailus wrote:
Hi Ivaylo,

On Sat, Apr 16, 2016 at 11:12:20AM +0300, Ivaylo Dimitrov wrote:
Some sensors (like the one in Nokia N900) provide metadata in the first
couple of lines. Make that information information available to the

Signed-off-by: Ivaylo Dimitrov <ivo.g.dimitrov.75@xxxxxxxxx>
drivers/media/i2c/smiapp/smiapp-core.c | 12 ++++++++++++
drivers/media/i2c/smiapp/smiapp.h | 1 +
2 files changed, 13 insertions(+)


I'm afraid I think this is not exactly the best way to approach the issue.
It'd work, somehow, yes, but ---

1. A compliant sensor (at least in theory) is able to tell this information
itself. The number of metadata lines is present in the sensor frame format

Right. And this is where that number is taken from in the patch and made available to whoever wants to use it. See . I don't really understand your point here. Maybe the patch description is fuzzy? Could you elaborate?

2. The more generic problem of describing the frame layout should be solved.
Sensor metadata is just a special case of this. I've proposed frame
descriptors (see an old RFC
<URL:>), but this is
just a partial solution as well; the APIs would need to be extended to
support metadata capture (I think Laurent has been working on that).

Could be, however what we have right now is Also, the patch is not trying to solve the problem with frame format description(or anything in general), but a mere way to pass an already available information in the sensor which is needed by omap3isp, by using an already existing API. I don't see how's that related to the way v4l API going to evolve in some (distant?) future. Not to say that once those frame format descriptors are available, it should be relatively easy to simply remove g_skip_top_lines form v4l2_subdev_sensor_ops and fix the drivers to use the new API.

BTW if you have any idea on how to pass (or set) the number of lines to be skipped at the start of the frame to omap3isp driver in some other way, I am fine with dropping the $subject patch and sending another one implementing your proposal.