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path: root/drivers/media/media-entity.c (follow)
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2016-04-29[media] media: change pipeline validation return errorHelen Mae Koike Fornazier1-1/+1
According to the V4L2 API, the VIDIOC_STREAMON ioctl should return EPIPE if there is a format mismatch in the pipeline configuration. As the .vidioc_streamon in the v4l2_ioctl_ops usually forwards the error caused by the v4l2_subdev_link_validate_default (if it is in use), it should return -EPIPE when it detect the mismatch. When an entity is connected to a non enabled link, media_entity_pipeline_start should return -ENOLINK, as the link does not exist. Signed-off-by: Helen Mae Koike Fornazier <helen.koike@collabora.co.uk> Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
2016-04-20[media] media-device: get rid of the spinlockMauro Carvalho Chehab1-8/+8
Right now, the lock schema for media_device struct is messy, since sometimes, it is protected via a spin lock, while, for media graph traversal, it is protected by a mutex. Solve this conflict by always using a mutex. As a side effect, this prevents a bug when the media notifiers is called at atomic context, while running the notifier callback: BUG: sleeping function called from invalid context at mm/slub.c:1289 in_atomic(): 1, irqs_disabled(): 0, pid: 3479, name: modprobe 4 locks held by modprobe/3479: #0: (&dev->mutex){......}, at: [<ffffffff81ce8933>] __driver_attach+0xa3/0x160 #1: (&dev->mutex){......}, at: [<ffffffff81ce8941>] __driver_attach+0xb1/0x160 #2: (register_mutex#5){+.+.+.}, at: [<ffffffffa10596c7>] usb_audio_probe+0x257/0x1c90 [snd_usb_audio] #3: (&(&mdev->lock)->rlock){+.+.+.}, at: [<ffffffffa0e6051b>] media_device_register_entity+0x1cb/0x700 [media] CPU: 2 PID: 3479 Comm: modprobe Not tainted 4.5.0-rc3+ #49 Hardware name: /NUC5i7RYB, BIOS RYBDWi35.86A.0350.2015.0812.1722 08/12/2015 0000000000000000 ffff8803b3f6f288 ffffffff81933901 ffff8803c4bae000 ffff8803c4bae5c8 ffff8803b3f6f2b0 ffffffff811c6af5 ffff8803c4bae000 ffffffff8285d7f6 0000000000000509 ffff8803b3f6f2f0 ffffffff811c6ce5 Call Trace: [<ffffffff81933901>] dump_stack+0x85/0xc4 [<ffffffff811c6af5>] ___might_sleep+0x245/0x3a0 [<ffffffff811c6ce5>] __might_sleep+0x95/0x1a0 [<ffffffff8155aade>] kmem_cache_alloc_trace+0x20e/0x300 [<ffffffffa0e66e3d>] ? media_add_link+0x4d/0x140 [media] [<ffffffffa0e66e3d>] media_add_link+0x4d/0x140 [media] [<ffffffffa0e69931>] media_create_pad_link+0xa1/0x600 [media] [<ffffffffa0fe11b3>] au0828_media_graph_notify+0x173/0x360 [au0828] [<ffffffffa0e68a6a>] ? media_gobj_create+0x1ba/0x480 [media] [<ffffffffa0e606fb>] media_device_register_entity+0x3ab/0x700 [media] Reviewed-by: Javier Martinez Canillas <javier@osg.samsung.com> Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com> Acked-by: Hans Verkuil <hans.verkuil@cisco.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
2016-03-05[media] media: add prefixes to interface typesShuah Khan1-17/+17
Add missing prefixes for DVB, V4L, and ALSA interface types. Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com> Acked-by: Hans Verkuil <hans.verkuil@cisco.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
2016-02-27[media] media: Media Controller non-locking __media_entity_pipeline_start/stop()Shuah Khan1-10/+24
Add non-locking __media_entity_pipeline_start/stop() interfaces to be called from code paths that hold the graph_mutex. Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
2016-02-27[media] media: Media Controller export non locking __media_entity_setup_link()Shuah Khan1-0/+1
Export __media_entity_setup_link() to be used from code paths that hold the graph_mutex. Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
2016-02-27[media] uapi/media.h: Declare interface types for ALSAShuah Khan1-0/+16
Declare the interface types to be used on alsa for the new G_TOPOLOGY ioctl. Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com> Acked-by: Takashi Iwai <tiwai@suse.de> Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
2016-02-19[media] media: Use all bits of an enumerationSakari Ailus1-2/+3
The allocation takes place in longs. Assign the size of the enum accordingly. Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
2016-02-01[media] media: Media Controller fix to not let stream_count go negativeShuah Khan1-6/+12
Change media_entity_pipeline_stop() to not decrement stream_count of an inactive media pipeline. Doing so, results in preventing starting the pipeline. Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
2016-01-11[media] media-entitiy: add a function to create multiple linksMauro Carvalho Chehab1-0/+65
Sometimes, it is desired to create 1:n and n:1 or even n:n links between different entities with the same function. This is actually needed to support DVB devices that have multiple frontends. While we could do a function like that internally at the DVB core, such function is generic enough to be at media-entity, and it could be useful on some other places. So, add such function. Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
2016-01-11[media] media-entity: increase max number of PADsMauro Carvalho Chehab1-1/+1
The DVB drivers may have 257 PADs. Get the next power of two that would accomodate that amount. Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
2016-01-11[media] media-device.h: use just one u32 counter for object IDMauro Carvalho Chehab1-20/+15
Instead of using one u32 counter per type for object IDs, use just one counter. With such change, it makes sense to simplify the debug logs too. Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
2016-01-11[media] move documentation to the header filesMauro Carvalho Chehab1-13/+0
Some exported functions were still documented at the .c file, instead of documenting at the .h one. Move the documentation to the right place, as we only use headers at media device-drivers.xml DocBook. Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
2016-01-11[media] media: Move MEDIA_ENTITY_MAX_PADS from media-entity.h to media-entity.cSakari Ailus1-0/+5
This isn't really a part of any interface drivers are expected to use. In order to keep drivers from using it, hide it in media-entity.c. This was always an arbitrary number and should be removed in the long run. Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
2016-01-11[media] media: Remove pre-allocated entity enumeration bitmapSakari Ailus1-11/+5
The bitmaps for entity enumerations used to be statically allocated. Now that the drivers have been converted to use the new interface which explicitly initialises the enum objects, drop the pre-allocated bitmaps. Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
2016-01-11[media] media: Keep using the same graph walk object for a given pipelineSakari Ailus1-6/+11
Initialise a given graph walk object once, and then keep using it whilst the same pipeline is running. Once the pipeline is stopped, release the graph walk object. Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
2016-01-11[media] media: Use entity enums in graph walkSakari Ailus1-10/+6
This will also mean that the necessary graph related data structures will be allocated dynamically, removing the need for maximum ID checks. Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
2016-01-11[media] media: Use the new media graph walk interfaceSakari Ailus1-1/+11
The media graph walk requires initialisation and cleanup soon. Update the users to perform the soon necessary API calls. Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
2016-01-11[media] media: Amend media graph walk API by init and cleanup functionsSakari Ailus1-0/+27
Add media_entity_graph_walk_init() and media_entity_graph_walk_cleanup() functions in order to dynamically allocate memory for the graph. This is not done in media_entity_graph_walk_start() as there are situations where e.g. correct error handling, that itself may not fail, requires successful graph walk. Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
2016-01-11[media] media: Move media graph state for streamon/off to the pipelineSakari Ailus1-8/+8
The struct media_entity_graph was allocated in the stack, limiting the number of entities that could be reasonably allocated. Instead, move the struct to struct media_pipeline which is typically allocated using kmalloc() instead. The intent is to keep the enumeration around for later use for the duration of the streaming. As streaming is eventually stopped, an unfortunate memory allocation failure would prevent stopping the streaming. As no memory will need to be allocated, the problem is avoided altogether. Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com> Reviewed-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
2016-01-11[media] media: Add an API to manage entity enumerationsSakari Ailus1-0/+40
This is useful in e.g. knowing whether certain operations have already been performed for an entity. The users include the framework itself (for graph walking) and a number of drivers. Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
2016-01-11[media] media-entity: cache media_device on object removalMauro Carvalho Chehab1-8/+18
As pointed by Dan, the commit f8fd4c61b5ae ("[media] media-entity: protect object creation/removal using spin lock")' leads to the following static checker warning: drivers/media/media-entity.c:781 media_remove_intf_link() error: dereferencing freed memory 'link' drivers/media/media-entity.c 777 void media_remove_intf_link(struct media_link *link) 778 { 779 spin_lock(&link->graph_obj.mdev->lock); 780 __media_remove_intf_link(link); 781 spin_unlock(&link->graph_obj.mdev->lock); In practice, I didn't see any troubles even with KASAN enabled. I guess gcc optimizer internally cached the mdev reference, instead of getting it twice. Yet, it is a very bad idea to rely on such optimization. So, let's fix the code. Reported-by: Dan Carpenter <dan.carpenter@oracle.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
2016-01-11[media] media-entity: use mutes for link setupMauro Carvalho Chehab1-2/+2
Changeset f8fd4c61b5ae ("[media] media-entity: protect object creation/removal using spin lock") changed the object creation/removal protection to spin lock, as this is what's used on media-device, keeping the mutex reserved for graph traversal routines. However, it also changed the link setup, by mistake. This could cause troubles, as the link setup can affect the graph traversal, and this is likely the reason for a mutex there. So, revert media_entity_setup_link() to use mutex. Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
2016-01-11[media] media: Enforce single entity->pipe in a pipelineSakari Ailus1-1/+6
If a different entity->pipe in a pipeline was encountered, a warning was issued but the execution continued as if nothing had happened. Return an error instead right there. Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
2016-01-11[media] media: move MEDIA_LNK_FL_INTERFACE_LINK logic to link creationMauro Carvalho Chehab1-2/+2
Instead of flagging an interface link as MEDIA_LNK_FL_INTERFACE_LINK only when returning to userspace, do it at link creation time. That would allow using such flag internally, and cleans up a little bit the code for G_TOPOLOGY ioctl. [mchehab@osg.samsung.com: folded with a fixup from Dan Carpenter, replacing & by &&] Suggested-by: Hans Verkuil <hans.verkuil@cisco.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
2016-01-11[media] media-entity: remove unneded enclosing parenthesisJavier Martinez Canillas1-2/+2
Commit 86ee417578a2 ("[media] media: convert links from array to list") had many changes that were automated using coccinelle but the semantic patch was not smart enough to rely on operators precedence and avoid using unnecessary enclosing parenthesis. This patch removes them since are not needed. Suggested-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
2016-01-11[media] media-entity.h: move kernel-doc tags from media-entity.cMauro Carvalho Chehab1-152/+11
Several additional functions are described at media-entity.c. Moving them to the header file, to make the code cleaner and to have all such macros at the same place. Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
2016-01-11[media] media_entity: rename media_obj functions to *_create *_destroyMauro Carvalho Chehab1-13/+13
Those media_obj_* functions are actually creating/destroying media graph objects. So, rename them to better represent what they're actually doing. No functional changes. This was created via this small shell script: for i in $(git grep -l media_gobj_init); do sed s,media_gobj_init,media_gobj_create,g <$i >a && mv a $i; done for i in $(git grep -l media_gobj_remove); do sed s,media_gobj_remove,media_gobj_destroy,g <$i >a && mv a $i; done Suggested-by: Sakari Ailus <sakari.ailus@iki.fi> Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
2016-01-11[media] media_entity: get rid of a unused varMauro Carvalho Chehab1-4/+1
> > > + if (rlink != link->reverse) { > > > + r++; > > > > The variable is incremented here but otherwise never used, you can remove it. Suggested-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
2016-01-11[media] media-entity: get rid of forward __media_entity_remove_link() declarationMauro Carvalho Chehab1-35/+32
Move this function to happen earlier, in order to avoid a uneeded forward declaration. Suggested-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
2016-01-11[media] media: remove extra blank linesMauro Carvalho Chehab1-3/+0
No functional changes. Suggested-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
2016-01-11[media] media-entity.h: convert media_entity_cleanup to inlineMauro Carvalho Chehab1-6/+0
This function was used in the past to free the links that were allocated by the media controller core. However, this is not needed anymore. We should likely get rid of the funcion on some function, but, for now, let's just convert into an inlined function and let the compiler to get rid of it. Suggested-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
2016-01-11[media] media framework: rename pads init function to media_entity_pads_init()Mauro Carvalho Chehab1-7/+4
With the MC next gen rework, what's left for media_entity_init() is to just initialize the PADs. However, certain devices, like a FLASH led/light doesn't have any input or output PAD. So, there's no reason why calling media_entity_init() would be mandatory. Also, despite its name, what this function actually does is to initialize the PADs data. So, rename it to media_entity_pads_init() in order to reflect that. The media entity actual init happens during entity register, at media_device_register_entity(). We should move init of num_links and num_backlinks to it. Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
2016-01-11[media] media-entity: init pads on entity init if was registered beforeJavier Martinez Canillas1-0/+10
If an entity is registered with a media device before is initialized with media_device_register_entity(), the number of pads won't be set so media_device_register_entity() won't create pad objects and add it to the media device pads list. Do this at entity initialization time if the entity was registered before so the graph is complete and correct regardless of the order in which the entities are initialized and registered. Suggested-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com> Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
2016-01-11[media] media_entity: remove gfp_flags argumentMauro Carvalho Chehab1-3/+2
We should not be creating device nodes at IRQ contexts. So, the only flags we'll be using will be GFP_KERNEL. Let's remove the gfp_flags, in order to make the interface simpler. If we ever need it, it would be easy to revert those changes. While here, remove an extra blank line. Suggested-by: Sakari Ailus <sakari.ailus@iki.fi> Acked-by: Hans Verkuil <hans.verkuil@cisco.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
2016-01-11[media] media-device: supress backlinks at G_TOPOLOGY ioctlMauro Carvalho Chehab1-0/+1
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. Acked-by: Hans Verkuil <hans.verkuil@cisco.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
2016-01-11[media] media-entity: fix backlink removal on __media_entity_remove_link()Mauro Carvalho Chehab1-3/+3
The logic is testing if num_links==0 at the wrong place. Due to that, a backlink may be kept without removal, causing KASAN to complain about usage after free during either entity or link removal. Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
2016-01-11[media] media: don't try to empty links list in media_entity_cleanup()Javier Martinez Canillas1-7/+0
The media_entity_cleanup() function only cleans up the entity links list but this operation is already made in media_device_unregister_entity(). In most cases this should be harmless (besides having duplicated code) since the links list would be empty so the iteration would not happen but the links list is initialized in media_device_register_entity() so if a driver fails to register an entity with a media device and clean up the entity in the error path, a NULL deference pointer error will happen. So don't try to empty the links list in media_entity_cleanup() since is either done already or haven't been initialized yet. Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
2016-01-11[media] media-entity: protect object creation/removal using spin lockMauro Carvalho Chehab1-8/+8
Some parts of the media controller are using mutexes while others are using spin locks in order to protect creation and removal of elements in the graph. That's wrong! Also, the V4L2 core can remove graph elements on non-interactive context: BUG: sleeping function called from invalid context at include/linux/sched.h:2776 Fix it by always using spin locks for graph element addition/removal, just like entity creation/removal is protected at media-device.c Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
2016-01-11[media] media-device: remove interfaces and interface linksMauro Carvalho Chehab1-1/+5
Just like what's done with entities, when the media controller is unregistered, release any interface and interface links that might still be there. Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
2016-01-11[media] media-entity: unregister entity linksMauro Carvalho Chehab1-0/+23
Add functions to explicitly unregister all entity links. This function is called automatically when an entity link is destroyed. Acked-by: Hans Verkuil <hans.verkuil@cisco.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
2016-01-11[media] media_device: add a topology version fieldMauro Carvalho Chehab1-0/+5
Every time a graph object is added or removed, the version of the topology changes. That's a requirement for the new MEDIA_IOC_G_TOPOLOGY, in order to allow userspace to know that the topology has changed after a previous call to it. Acked-by: Hans Verkuil <hans.verkuil@cisco.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
2016-01-11[media] media-device: add pads and links to media_deviceMauro Carvalho Chehab1-11/+6
The MC next gen API sends objects to userspace grouped by their types. In the case of pads and links, in order to improve performance and have a simpler code, the best is to store them also on separate linked lists at MC. If we don't do that, we would need this kind of interaction to send data to userspace (code is in structured english): for each entity: for each pad: store pads for each entity: for each link: store link for each interface: for each link: store link With would require one nested loop for pads and two nested loops for links. By using separate linked lists for them, just one loop would be enough. Acked-by: Hans Verkuil <hans.verkuil@cisco.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
2016-01-11[media] media: move mdev list init to gobjMauro Carvalho Chehab1-3/+12
Let's control the topology changes inside the graph_object. So, move the addition and removal of interfaces/entities from the mdev lists to media_gobj_init() and media_gobj_remove(). The main reason is that mdev should have lists for all object types, as the new MC api will require to store objects in separate places. Acked-by: Hans Verkuil <hans.verkuil@cisco.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
2016-01-11[media] media: report if a pad is sink or source at debug msgMauro Carvalho Chehab1-2/+5
Sometimes, it is important to see if the created pad is sink or source. Add info to track that. Acked-by: Hans Verkuil <hans.verkuil@cisco.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
2016-01-11[media] media: add a linked list to track interfaces by mdevMauro Carvalho Chehab1-0/+3
The media device should list the interface objects, so add a linked list for those interfaces in struct media_device. Acked-by: Hans Verkuil <hans.verkuil@cisco.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
2016-01-11[media] media-entity: add a helper function to create interfaceMauro Carvalho Chehab1-9/+14
As we'll be adding other interface types in the future, put the common interface create code on a separate function. Suggested-by: Hans Verkuil <hans.verkuil@cisco.com> Acked-by: Hans Verkuil <hans.verkuil@cisco.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
2016-01-11[media] media: add support to link interfaces and entitiesMauro Carvalho Chehab1-0/+38
Now that we have a new graph object called "interfaces", we need to be able to link them to the entities. Add a linked list to the interfaces to allow them to be linked to the entities. Acked-by: Hans Verkuil <hans.verkuil@cisco.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
2016-01-11[media] media: make link debug printk more genericMauro Carvalho Chehab1-7/+5
Remove entity name from the link as this exists only if the object type is PAD on both link ends. Acked-by: Hans Verkuil <hans.verkuil@cisco.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
2016-01-11[media] media: make add link more genericMauro Carvalho Chehab1-4/+4
The media_entity_add_link() function takes an entity as an argument just to get the list head. Make it more generic by changing the function argument to list_head. No functional changes. Acked-by: Hans Verkuil <hans.verkuil@cisco.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
2016-01-11[media] media: convert links from array to listMauro Carvalho Chehab1-65/+63
The entire logic that represent graph links were developed on a time where there were no needs to dynamic remove links. So, although links are created/removed one by one via some functions, they're stored as an array inside the entity struct. As the array may grow, there's a logic inside the code that checks if the amount of space is not enough to store the needed links. If it isn't the core uses krealloc() to change the size of the link, with is bad, as it leaves the memory fragmented. So, convert links into a list. Also, currently, both source and sink entities need the link at the graph traversal logic inside media_entity. So there's a logic duplicating all links. That makes it to spend twice the memory needed. This is not a big deal for today's usage, where the number of links are not big. Yet, if during the MC workshop discussions, it was said that IIO graphs could have up to 4,000 entities. So, we may want to remove the duplication on some future. The problem is that it would require a separate linked list to store the backlinks inside the entity, or to use a more complex algorithm to do graph backlink traversal, with is something that the current graph traversal inside the core can't cope with. So, let's postpone a such change if/when it is actually needed. It should also be noticed that the media_link structure uses 44 bytes on 32-bit architectures and 84 bytes on 64-bit architecture. It will thus be allocated out of the 64-bytes and 96-bytes pools respectively. That's a 12.5% memory waste on 64-bit architectures and 31.25% on 32-bit architecture. A linked list is less efficient than an array in this case, but this could later be optimized if we can get rid of the reverse links (with would reduce memory allocation by 50%). Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>