| Message ID | 7cc4f0ce2266e6300d349535e705941a190398e9.1441559233.git.mchehab@osg.samsung.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 09/06/2015 07:30 PM, Mauro Carvalho Chehab wrote: > Due to the graph traversal algorithm currently in usage, we > need a copy of all data links. Those backlinks should not be > send to userspace, as otherwise, all links there will be > duplicated. > > Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com> Acked-by: Hans Verkuil <hans.verkuil@cisco.com> > > diff --git a/drivers/media/media-device.c b/drivers/media/media-device.c > index 0238885fcc74..97eb97d9b662 100644 > --- a/drivers/media/media-device.c > +++ b/drivers/media/media-device.c > @@ -333,6 +333,9 @@ static long __media_device_get_topology(struct media_device *mdev, > /* Get links and number of links */ > i = 0; > media_device_for_each_link(link, mdev) { > + if (link->is_backlink) > + continue; > + > i++; > > if (ret || !topo->links) > diff --git a/drivers/media/media-entity.c b/drivers/media/media-entity.c > index cd4d767644df..4868b8269204 100644 > --- a/drivers/media/media-entity.c > +++ b/drivers/media/media-entity.c > @@ -648,6 +648,7 @@ media_create_pad_link(struct media_entity *source, u16 source_pad, > backlink->source = &source->pads[source_pad]; > backlink->sink = &sink->pads[sink_pad]; > backlink->flags = flags; > + backlink->is_backlink = true; > > /* Initialize graph object embedded at the new link */ > media_gobj_init(sink->graph_obj.mdev, MEDIA_GRAPH_LINK, > diff --git a/include/media/media-entity.h b/include/media/media-entity.h > index e1a89899deef..3d389f142a1d 100644 > --- a/include/media/media-entity.h > +++ b/include/media/media-entity.h > @@ -96,6 +96,7 @@ struct media_pipeline { > * @reverse: Pointer to the link for the reverse direction of a pad to pad > * link. > * @flags: Link flags, as defined at uapi/media.h (MEDIA_LNK_FL_*) > + * @is_backlink: Indicate if the link is a backlink. > */ > struct media_link { > struct media_gobj graph_obj; > @@ -112,6 +113,7 @@ struct media_link { > }; > struct media_link *reverse; > unsigned long flags; > + bool is_backlink; > }; > > /** > -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Hi Mauro, Thank you for the patch. On Sunday 06 September 2015 14:30:47 Mauro Carvalho Chehab wrote: > Due to the graph traversal algorithm currently in usage, we > need a copy of all data links. Those backlinks should not be > send to userspace, as otherwise, all links there will be > duplicated. > > Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com> > > diff --git a/drivers/media/media-device.c b/drivers/media/media-device.c > index 0238885fcc74..97eb97d9b662 100644 > --- a/drivers/media/media-device.c > +++ b/drivers/media/media-device.c > @@ -333,6 +333,9 @@ static long __media_device_get_topology(struct > media_device *mdev, /* Get links and number of links */ > i = 0; > media_device_for_each_link(link, mdev) { > + if (link->is_backlink) > + continue; > + > i++; > > if (ret || !topo->links) > diff --git a/drivers/media/media-entity.c b/drivers/media/media-entity.c > index cd4d767644df..4868b8269204 100644 > --- a/drivers/media/media-entity.c > +++ b/drivers/media/media-entity.c > @@ -648,6 +648,7 @@ media_create_pad_link(struct media_entity *source, u16 > source_pad, backlink->source = &source->pads[source_pad]; > backlink->sink = &sink->pads[sink_pad]; > backlink->flags = flags; > + backlink->is_backlink = true; > > /* Initialize graph object embedded at the new link */ > media_gobj_init(sink->graph_obj.mdev, MEDIA_GRAPH_LINK, > diff --git a/include/media/media-entity.h b/include/media/media-entity.h > index e1a89899deef..3d389f142a1d 100644 > --- a/include/media/media-entity.h > +++ b/include/media/media-entity.h > @@ -96,6 +96,7 @@ struct media_pipeline { > * @reverse: Pointer to the link for the reverse direction of a pad to pad > * link. > * @flags: Link flags, as defined at uapi/media.h (MEDIA_LNK_FL_*) > + * @is_backlink: Indicate if the link is a backlink. > */ > struct media_link { > struct media_gobj graph_obj; > @@ -112,6 +113,7 @@ struct media_link { > }; > struct media_link *reverse; > unsigned long flags; > + bool is_backlink; I agree with the purpose of this patch (and as stated for other patches in the series I believe you should squash it with the patch that introduces the G_TOPOLOGY ioctl) but I won't whether you couldn't do with the additional variable by adding a flag for backlinks (flag that wouldn't be shown to userspace). Now that I think about it an even better implementation could be to avoid creating backlinks at all. As links are now dynamically allocated you could have two struct list_head in the link structure, one for the source and one for the sink. It sounds too easy to be true, I wonder if I'm overlooking something. > }; > > /**
Em Mon, 23 Nov 2015 21:56:50 +0200 Laurent Pinchart <laurent.pinchart@ideasonboard.com> escreveu: > Hi Mauro, > > Thank you for the patch. > > On Sunday 06 September 2015 14:30:47 Mauro Carvalho Chehab wrote: > > Due to the graph traversal algorithm currently in usage, we > > need a copy of all data links. Those backlinks should not be > > send to userspace, as otherwise, all links there will be > > duplicated. > > > > Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com> > > > > diff --git a/drivers/media/media-device.c b/drivers/media/media-device.c > > index 0238885fcc74..97eb97d9b662 100644 > > --- a/drivers/media/media-device.c > > +++ b/drivers/media/media-device.c > > @@ -333,6 +333,9 @@ static long __media_device_get_topology(struct > > media_device *mdev, /* Get links and number of links */ > > i = 0; > > media_device_for_each_link(link, mdev) { > > + if (link->is_backlink) > > + continue; > > + > > i++; > > > > if (ret || !topo->links) > > diff --git a/drivers/media/media-entity.c b/drivers/media/media-entity.c > > index cd4d767644df..4868b8269204 100644 > > --- a/drivers/media/media-entity.c > > +++ b/drivers/media/media-entity.c > > @@ -648,6 +648,7 @@ media_create_pad_link(struct media_entity *source, u16 > > source_pad, backlink->source = &source->pads[source_pad]; > > backlink->sink = &sink->pads[sink_pad]; > > backlink->flags = flags; > > + backlink->is_backlink = true; > > > > /* Initialize graph object embedded at the new link */ > > media_gobj_init(sink->graph_obj.mdev, MEDIA_GRAPH_LINK, > > diff --git a/include/media/media-entity.h b/include/media/media-entity.h > > index e1a89899deef..3d389f142a1d 100644 > > --- a/include/media/media-entity.h > > +++ b/include/media/media-entity.h > > @@ -96,6 +96,7 @@ struct media_pipeline { > > * @reverse: Pointer to the link for the reverse direction of a pad to > pad > > * link. > > * @flags: Link flags, as defined at uapi/media.h (MEDIA_LNK_FL_*) > > + * @is_backlink: Indicate if the link is a backlink. > > */ > > struct media_link { > > struct media_gobj graph_obj; > > @@ -112,6 +113,7 @@ struct media_link { > > }; > > struct media_link *reverse; > > unsigned long flags; > > + bool is_backlink; > > I agree with the purpose of this patch (and as stated for other patches in the > series I believe you should squash it with the patch that introduces the > G_TOPOLOGY ioctl) but I won't whether you couldn't do with the additional > variable by adding a flag for backlinks (flag that wouldn't be shown to > userspace). > > Now that I think about it an even better implementation could be to avoid > creating backlinks at all. As links are now dynamically allocated you could > have two struct list_head in the link structure, one for the source and one > for the sink. It sounds too easy to be true, I wonder if I'm overlooking > something. I tried that. This was actually one of my pans. However, it is not as trivial as it seems. I explored several different alternatives: 1) we could have two lists at struct media_entity, one for links and another one for backlinks: struct media_link { ... struct list_head list; ... }; struct media_entity { ... struct list_head links; struct list_head backlinks; ... }; And add the link to either one of the list. However, in such case, container_of() would not work, because the offset of the data at the struct media_entity will be different, if the link is at the links or backlinks list. 2) to have 2 lists also at struct media_link, one for the links and another one for the backlinks, but this will require non trivial changes at the graph traversal logic. I can foresee some other alternatives that I didn't try yet: - to use a separate data struct for the backlinks, like: struct media_obj_group { struct *media_object; struct list_head list; } and use this to store backlinks. Again, would require nontrivial changes at the graph traversal logic and would end by spending some extra memory for the backlinks; - using the same structs as already defined, patching all routines that use links to add the capability for them to identify if the link is actually a backlink. This would be non-trivial and may be messy. So, while I would love to get rid of backlinks, fixing it is not trivial at all. Regards, Mauro -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/media/media-device.c b/drivers/media/media-device.c index 0238885fcc74..97eb97d9b662 100644 --- a/drivers/media/media-device.c +++ b/drivers/media/media-device.c @@ -333,6 +333,9 @@ static long __media_device_get_topology(struct media_device *mdev, /* Get links and number of links */ i = 0; media_device_for_each_link(link, mdev) { + if (link->is_backlink) + continue; + i++; if (ret || !topo->links) diff --git a/drivers/media/media-entity.c b/drivers/media/media-entity.c index cd4d767644df..4868b8269204 100644 --- a/drivers/media/media-entity.c +++ b/drivers/media/media-entity.c @@ -648,6 +648,7 @@ media_create_pad_link(struct media_entity *source, u16 source_pad, backlink->source = &source->pads[source_pad]; backlink->sink = &sink->pads[sink_pad]; backlink->flags = flags; + backlink->is_backlink = true; /* Initialize graph object embedded at the new link */ media_gobj_init(sink->graph_obj.mdev, MEDIA_GRAPH_LINK, diff --git a/include/media/media-entity.h b/include/media/media-entity.h index e1a89899deef..3d389f142a1d 100644 --- a/include/media/media-entity.h +++ b/include/media/media-entity.h @@ -96,6 +96,7 @@ struct media_pipeline { * @reverse: Pointer to the link for the reverse direction of a pad to pad * link. * @flags: Link flags, as defined at uapi/media.h (MEDIA_LNK_FL_*) + * @is_backlink: Indicate if the link is a backlink. */ struct media_link { struct media_gobj graph_obj; @@ -112,6 +113,7 @@ struct media_link { }; struct media_link *reverse; unsigned long flags; + bool is_backlink; }; /**
Due to the graph traversal algorithm currently in usage, we need a copy of all data links. Those backlinks should not be send to userspace, as otherwise, all links there will be duplicated. Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>