On 4/9/19 3:59 PM, Laurent Pinchart wrote:
Hi Steve, On Tue, Apr 09, 2019 at 03:22:47PM -0700, Steve Longerbeam wrote:On 4/9/19 1:57 PM, Laurent Pinchart wrote:On Mon, Apr 08, 2019 at 08:58:25PM -0700, Steve Longerbeam wrote:On 4/8/19 4:12 AM, Niklas Söderlund wrote:On 2019-04-05 17:04:50 -0700, Steve Longerbeam wrote:On 4/5/19 9:16 AM, Eugeniu Rosca wrote:Hi Niklas, Jacopo cc: Steve Apologize for reviving this old thread. Just one question below. On 2018-05-24 10:14:52, Niklas Söderlund wrote: [..]+ #define vin_to_source(vin) ((vin)->parallel->subdev)This in particular I hate and at some point I hope to remove it or move it to rcar-v4l2.c. :-) But that is a task for later and not related to your patch-set.What about below patch excerpt (courtesy of Steve) which is currently under review in our tree? If we are on the same page here, we would happily contribute a patch to you based on below.I can submit this patch to media-tree ML for formal review.I see no problem with the patch itself but as you point out bellow there are other patches which makes of the change I assume? The change to vin_to_source() on it's own would not add much value as vin_to_source() is currently only used in the none-mc parts of the driver where the change bellow would never be used. My dream would be to one day drop the none-mc mode of this driver, or split it out to a rcar-vin-legacy module or something ;-)Yes, that's something that has been confusing me. Why does there need to be a distinction between a media control mode non-mc mode in the rcar-vin driver? I understand the "digital"/"parallel" mode is to handle sensors with a parallel interface (as opposed to MIPI CSI-2), but why not make the parallel sensors also require media-control (enabling/disable media links, etc.)?But there are also other patches to rcar-vin applied to the tree mentioned by Eugeniu, which can broadly be described as: 1. If the rcar-csi2 sub-device's source pad format is changed via media-ctl, the connected VIN's crop bounds (vin->source rectangle) will be stale, since vin->source must always be equal to the source pad rectangle. So we have a patch that will catch the asynchronous V4L2_EVENT_SOURCE_CHANGE event sent from the rcar-csi2 sub-device when its source pad format is changed. In response, the VIN connected to that rcar-csi2 sub-device will reset the crop bounds to the new source pad format rectangle. In order to make this work however...I'm no expert on when the crop/selection rectangles shall be reset and have wrestled with this in the past for this driver. I have partial rework of how formats especially crop/selection works planed. My goal of that is to try and make it simpler and more straight forward taking ideas from the vivid driver. There are some limitations in my implementation of this in the current driver which prevents me from adding sequential formats and enable the UDS scaler.Ok. What I did for imx-media driver is to export a function from the video capture interface that allows the source sub-device connected to the capture interface to call it when the source pad format changes, which gives the capture interface the chance to adjust compose windowThat sounds like a big hack, the two devices should be independent. Let's not replicate this, and it should be fixed in the imx driver.I admit it's a bit of a hack, but it is there to get around a limitation of media/v4l2 framework. And the two devices are not independent, they are connected the same way other media entities are connected. The media-ctl tool will take care of propagating formats from connected source -> sink sub-devices, but it stops at the sub-device -> video_device interface. First, this propagation should happen in the kernel at the time a source pad format is modified, rather than by a user tool, because it is a media/v4l2 core requirement that source -> sink formats must be equal before streaming starts.That's not right. It's a requirement that the formats are compatible to start streaming, but it's not a requirement *before* starting streaming. That's why kernel drivers must not propagate formats between entities, only within an entity. Doing in-kernel propagation between entities is an API violation.Second, a source pad format change should also be propagated to connected video devices. Userland is then free to make modifications to the video_device format if the latter supports cropping/scaling etc., but the default should be to reset the format at the time the connected sub-device format has changed.For the same reason above, the format on video nodes must be set by applications. Could you please fix it in the imx driver ?
Well, if it's an API violation then I'll remove it. But removing the propagation will put (more) burden on userland. In imx the sub-device does the cropping and scaling, but the video_device connected to it does not. Which means the compose rectangle in the video_device must always be the same as the sub-device compose rectangle.
Does sending the V4L2_EVENT_SOURCE_CHANGE event to automatically reset the video_device format when the sub-device format changes also violate the API? I don't see why it would, it's just making use of the event mechanism. If you agree then I will do the same in imx, and offer it as a patch to rcar-vin (to ensure the rcar video_device's crop bounds are always correct).
If you don't agree then perhaps imx and rcar-vin can at least do the equivalent of v4l2-core, which is to ensure the video_device formats are compatible with the connected sub-device before streaming can start.
Steve
(unlike rcar-vin, imx capture interface doesn't crop or scale, the connected source subdev does that, but it does pad the compose window so it needs to know the original compose window, sorry hope I haven't lost you). Anyway I think catching the V4L2_EVENT_SOURCE_CHANGE event is maybe a cleaner way to update the crop bounds in rcar-vin than using an exported function.2. Sub-device events need to be forwarded to the VIN's that have enabled media links to the reporting sub-device. Currently, sub-device events are only forwarded to VIN7, because the notifier is registered only from VIN7, and so the sub-devices are registered only to the v4l2_dev owned by VIN7. So we have a set of patches that fix this: sub-device events get forwarded to the VIN's that have connected media paths to that sub-device. Besides allowing to reset the VIN crop bounds rectangle asynchronously, this also seems to be logically the correct behavior. It also makes the user interface a little more intuitive: userland knows which VIN it is capturing on, and that is the same VIN that will be receiving sub-device events in the active pipeline.This is a problem I ponder from time to time, happy to hear I'm not the only one :-) My view is that events are somewhat not functional in the media controller world and should be fixed at the framework level, maybe by moving them from the vdev to the mdev :-)How about embedding the 'struct v4l2_device' into 'struct rvin_group' instead of 'struct rvin_dev'? That probably makes more sense, the v4l2_dev keeps track of media-device-wide info such as the list of sub-devices in the graph, so it seems more appropriate to create only one instance of v4l2_dev. That will force rcar-vin to lookup the correct VINs to forward the event to, since v4l2_dev is no longer attached to the VINs. But moving events from v4l2 to media (e.g. media entities send events to the mdev, rather than v4l2 sub-devices sending events to the v4l2_dev) is also an interesting idea.I think it's great that you worked on the problem but I'm a bit concerned with addressing this on a driver basis. Maybe this is something to bring up at the next v4l2 summit? I might be wrong here and there already is a consensus to address this as you describe in each driver. Do you have any insights on the topic?I haven't been tuned into that topic, but yes I agree that events need a better framework.3. We have some patches under review that allow alternate -> none field mode. That is, source sub-device is sending alternate fields (top, bottom, top, ...), and userland is configured to receive those fields unmodified by setting field type to none. rcar-dma then detects and reports the field type of the captured field (top or bottom) in (struct v4l2_buffer)->field. Doing this allows for de-interlacing the captured fields using the FDP1 mem2mem device.Interesting, maybe I'm missing something but would it not be a better solution to add support for V4L2_FIELD_ALTERNATE to rcar-vin instead of abusing V4L2_FIELD_NONE?Well, from 6c51f646f6 ("media: rcar-vin: fix handling of single field frames (top, bottom and alternate fields)"), "There was never proper support in the VIN driver to deliver ALTERNATING field format to user-space, remove this field option. The problem is that ALTERNATING field order requires the sequence numbers of buffers returned to userspace to reflect if fields were dropped or not, something which is not possible with the VIN drivers capture logic." Is that still a concern, or can alternate mode be brought back but with possibly the above limitation? Also, there is this paragraph in [1] regarding V4L2_FIELD_NONE, so it sounds like using this field type in this way may not be too much abuse :) "Images are in progressive format, not interlaced. The driver may also indicate this order when it cannot distinguish between|V4L2_FIELD_TOP|and|V4L2_FIELD_BOTTOM|." [1] https://linuxtv.org/downloads/v4l-dvb-apis/uapi/v4l/field-order.htmlThere are some other miscellaneous patches that I can submit, but the above describes the bulk of the changes.I'm happy to see work being done on the driver and would of course like to help you get all changes upstream so that all your use-cases would work out-of-the-box.Before I start on porting these patches to the media-tree, do the above changes make general sense, or are there fundamental problems with those ideas?Subject: [PATCH] media: rcar-vin: Generalize vin_to_source() Change the vin_to_source() macro to an inline function that will retrieve the source subdevice for both media-control and non media-control mode. Signed-off-by: Steve Longerbeam <steve_longerbeam@xxxxxxxxxx> --- [..] diff --git a/drivers/media/platform/rcar-vin/rcar-vin.h b/drivers/media/platform/rcar-vin/rcar-vin.h index 0b13b34d03e3..29d8c4a80c35 100644 --- a/drivers/media/platform/rcar-vin/rcar-vin.h +++ b/drivers/media/platform/rcar-vin/rcar-vin.h @@ -217,7 +217,21 @@ struct rvin_dev { v4l2_std_id std; }; -#define vin_to_source(vin) ((vin)->parallel->subdev) +static inline struct v4l2_subdev * +vin_to_source(struct rvin_dev *vin) +{ + if (vin->info->use_mc) { + struct media_pad *pad; + + pad = media_entity_remote_pad(&vin->pad); + if (!pad) + return NULL; + + return media_entity_to_v4l2_subdev(pad->entity); + } + + return vin->parallel->subdev; +} /* Debug */ #define vin_dbg(d, fmt, arg...) dev_dbg(d->dev, fmt, ##arg)
