Em 05-10-2011 17:54, Laurent Pinchart escreveu:
Hi Hans,
On Tuesday 04 October 2011 09:03:59 Hans Verkuil wrote:
On Tuesday, October 04, 2011 07:31:27 Mauro Carvalho Chehab wrote:
Em 03-10-2011 19:37, Javier Martinez Canillas escreveu:
On Mon, Oct 3, 2011 at 11:56 PM, Mauro Carvalho Chehab wrote:
Em 03-10-2011 18:44, Laurent Pinchart escreveu:
On Monday 03 October 2011 21:16:45 Mauro Carvalho Chehab wrote:
Em 03-10-2011 08:53, Laurent Pinchart escreveu:
On Monday 03 October 2011 11:53:44 Javier Martinez Canillas wrote:
[snip]
Laurent, I have a few questions about MCF and the OMAP3ISP driver
if you are so kind to answer.
1- User-space programs that are not MCF aware negotiate the format
with the V4L2 device (i.e: OMAP3 ISP CCDC output), which is a sink
pad. But the real format is driven by the analog video format in
the source pad (i.e: tvp5151).
That's not different from existing systems using digital sensors,
where the format is driven by the sensor.
I modified the ISP driver to get the data format from the source
pad and set the format for each pad on the pipeline accordingly
but I've read from the documentation [1] that is not correct to
propagate a data format from source pads to sink pads, that the
correct thing is to do it from sink to source.
So, in this case an administrator has to externally configure the
format for each pad and to guarantee a coherent format on the
whole pipeline?.
That's correct (except you don't need to be an administrator to do
so
:-)).
NACK.
Double NACK :-D
When userspace sends a VIDIOC_S_STD ioctl to the sink node, the
subdevs that are handling the video/audio standard should be
changed, in order to obey the V4L2 ioctl. This is what happens with
all other drivers since the beginning of the V4L1 API. There's no
reason to change it, and such change would be a regression.
The same could have been told for the format API:
"When userspace sends a VIDIOC_S_FMT ioctl to the sink node, the
subdevs that are handling the video format should be changed, in
order to obey the V4L2 ioctl. This is what happens with all other
drivers since the beginning of the V4L1 API. There's no reason to
change it, and such change would be a regression."
But we've introduced a pad-level format API. I don't see any reason
to treat standard differently.
Neither do I. The pad-level API should not replace the V4L2 API for
standard, for controls and/or for format settings.
Remember we are talking about the subdev driver here. It makes no sense to
have both a s_mbus_fmt video op and a set_fmt pad op, which both do the
same thing. Bridge drivers should be adapted to use set_fmt only, so we
can drop s_mbus_fmt.
BTW, the names 'set_fmt' and 'get_fmt' are very confusing to me. I always
think these refer to v4l2_format. Can we please rename this to
g/s_mbus_fmt?
Shouldn't we do it the other way around, renaming the g/s_mbus_fmt video
operations to g/s_fmt, now that we only have mbus formats left ? The operation
names would be shorter.
And set/get_crop to s/g_crop? This for consistent naming.
set/get_crop will be replaced with set/get_selection (or s/g_selection if you
like that better :-)).
When it comes to S_STD I don't see the need for a pad version of this. It
is an op that is used to configure subdevs to handle a specific standard.
If you are configuring the pipelines manually, then after calling S_STD
you have to set up the mbus formats yourself.
Of course, I can generate scenarios where you would need to set the
standard through the subdev node (i.e. two video receivers connected to a
SoC, one receiving PAL, the other receiving NTSC, and both streams
composed into a single new stream that's DMA-ed to memory), but frankly,
those scenarios are very contrived :-)
Unless I don't understand this correctly, I think those two paragraphs are not
related.
Regarding the pad-level standard operations, you're probably right. Subdevs
that can handle two or more analog streams at the same time would need that,
but we probably won't need to support them any time soon (if ever). So we
could keep the subdev-level standard operations, with the implicit (or
explicit) rule that they apply to the currently selected input of the subdev
(I suppose TV decoders with an input mux are not uncommon).
Switching from one input to the other doesn't switch the TV format (except,
of course, if autodetection is enabled). The driver should keep the last settings
to the new input for resolution, format, fourcc and image controls.
Regarding controlling standards directly on subdevs, I think that's the way to
go for complex pipelines, but that doesn't require pad-level standard
operations.
The preset ioctls would be more realistic since I know that a scenario like
the one above does exist for e.g. HDMI inputs, where each can receive a
different format.
In that case the preset ioctls would have to be exposed to the subdev
nodes, allowing you to set it up for each HDMI receiver independently. But
you still do not need pads to do this since this is a subdev-level
operation, not pad-level.
Or does exist a way to do this automatic?. i.e: The output entity
on the pipeline promotes the capabilities of the source pad so
applications can select a data format and this format gets
propagated all over the pipeline from the sink pad to the source?
It can be automated in userspace (through a libv4l plugin for
instance), but it's really not the kernel's job to do so.
It is a kernel job to handle VIDIOC_S_STD, and not a task to be left
to any userspace plugin.
And VIDIOC_S_FMT is handled by userspace for the OMAP3 ISP today. Why
are standards different ?
All v4l media devices have sub-devices with either tv decoders or
sensors connected into a sink. The sink implements the /dev/video?
node.
When an ioctl is sent to the v4l node, the sensors/decoders are
controlled to implement whatever is requested: video standards,
formats etc.
Changing it would be a major regression. If OMAP3 is not doing the
right thing, it should be fixed, and not the opposite.
That is the approach we took, we hack the isp v4l2 device driver
(ispvideo) to bypass the ioctls to the sub-device that as the source
pad (tvp5151 in our case, but it could be a sensor as well). So, for
example the VIDIOC_S_STD ioctl handler looks like this (I post a
simplified version of the code, just to give an idea):
static int isp_video_s_std(struct file *file, void *fh, v4l2_std_id
*norm) {
struct isp_video *video = video_drvdata(file);
struct v4l2_subdev *sink_subdev;
struct v4l2_subdev *source_subdev;
sink_subdev = isp_video_remote_subdev(video, NULL);
sink_pad =&sink_subdev->entity.pads[0];
source_pad = media_entity_remote_source(sink_pad);
source_subdev = media_entity_to_v4l2_subdev(source_pad->entity);
v4l2_subdev_call(source_subdev, core, s_std, NULL, norm);
}
So applications interact with the /dev/video? via V4L2 ioctls whose
handlers call the sub-dev functions. Is that what you propose?
Something like that. For example:
static int vidioc_s_std(struct file *file, void *priv, v4l2_std_id *norm)
{
/* Do some sanity test/resolution adjustments, etc */
v4l2_device_call_all(&dev->v4l2_dev, 0, core, s_std, dev->norm);
return 0;
}
It should be noticed that:
1) a full standard auto-detection is only possible at the V4L2 level, as
a standard is a composition of audio and video carriers. I intend to
work tomorrow to add audio auto-detection to pvrusb2;
2) a full s_std should not only adjust the TV demod pad, but also, the
audio pad and the tuner pad (if the analog input comes from a tuner).
The MC/subdev API is there to fill the blanks, e. g. to handle cases
where the same function could be implemented on two different places
of the pipeline, e. g. when both the sensor and the bridge could do
scaling, and userspace wants to explicitly use one, or the other, but
it were never meant to replace the V4L2 functionality.
[1]: http://linuxtv.org/downloads/v4l-dvb-apis/subdev.html
2- If the application want a different format that the default
provided by the tvp5151, (i.e: 720x576 for PAL), where do I have
to crop the image? I thought this can be made using the CCDC,
copying less lines to memory or the RESIZER if the application
wants a bigger image. What is the best approach for this?
Not sure if I understood your question, but maybe you're mixing two
different concepts here.
If the application wants a different image resolution, it will use
S_FMT. In this case, what userspace expects is that the driver will
scale, if supported, or return -EINVAL otherwise.
With the OMAP3 ISP, which is I believe what Javier was asking about,
the application will set the format on the OMAP3 ISP resizer input
and output pads to configure scaling.
Yes, that was my question about. But still is not clear to me if
configuring the ISP resizer input and output pads with different frame
sizes automatically means that I have to do the scale or this has to
be configured using a S_FMT ioctl to the /dev/video? node.
Basically what I don't know is when I have to modify the pipeline
graph inside the ISP driver and when this has to be made from
user-space via MCF.
In the specific case of analog inputs, In general, better results are
obtained if the scaling is done at the analog demod, as it can play with
the pixel sampling rate, and obtaining a better result than a decimation
filter. Not all demods accept this through.
Anyway, S_FMT is expected to work at the /dev/video? node. Laurent will
likely argument against, but, again, allowing to control the scaling on
a different place is a bonus of the MC/subdev API, but it should never
replace the S_FMT V4L2 call.
I agree with Mauro, up to a point. One way or another drivers should
support S_FMT through the video nodes.
When there's a one-to-one relationship between the video device (in the
hardware sense) and the video node, that's pretty normal. However, when a
video device is made of a complex pipeline and several video nodes, the
problem becomes much more complex and mapping a "simple" operations such as
S_FMT to hardware configuration becomes a policy decision.
One video node should "master" the operation. A V4L2 application will open just
one device to control the stuff (as a general rule, I'd say that it will open
the sink node). A V4L2 ioctl applied into it should be propagated along the
pipeline for the ioctl to happen. This is what happens with all other devices,
and this is what a V4L2 userspace application expects.
But if someone starts programming the pipeline through subdev nodes, then I
think it is reasonable that trying to call S_FMT would return EBUSY or
something similar.
It has been suggested that S_FMT can be implemented for such systems as a
libv4l2 plugin, but I would like to see code doing this first as I am not
convinced that that's the best way to do it.
Sakari, what's the status of the OMAP3 ISP libv4l plugin ?
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