There is a block of code in rvin_group_link_notify() that loops through
all entities in the media graph, and prevents enabling a link to a VIN
node if any entity is in use. This prevents enabling a VIN link even if
there is an in-use entity somewhere in the graph that is independent of
the link's pipeline.
For example, the code will prevent enabling a link from the first
rcar-csi2 receiver to a VIN node even if there is an enabled link
somewhere far upstream on the second independent rcar-csi2 receiver
pipeline.
If this code is meant to prevent modifying a link if any entity in the
graph is actively involved in streaming (because modifying the CHSEL
register fields can disrupt any/all running streams), then the entities
stream counts should be checked rather than the use counts.
(There is already such a check in __media_entity_setup_link() that verifies
the stream_count of the link's source and sink entities are both zero,
but that is insufficient, since there should be no running streams in
the entire graph).
Modify the media_device_for_each_entity() loop to check the entity
stream_count instead of the use_count, and elaborate on the comment.
VIN node links can now be enabled even if there are other independent
in-use entities that are not streaming.
Fixes: c0cc5aef31 ("media: rcar-vin: add link notify for Gen3")
Signed-off-by: Steve Longerbeam <[email protected]>
---
Changes in v2:
- bring back the media_device_for_each_entity() loop but check the
stream_count not the use_count.
---
drivers/media/platform/rcar-vin/rcar-core.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/drivers/media/platform/rcar-vin/rcar-core.c b/drivers/media/platform/rcar-vin/rcar-core.c
index f0719ce24b97..6dd6b11c1b2b 100644
--- a/drivers/media/platform/rcar-vin/rcar-core.c
+++ b/drivers/media/platform/rcar-vin/rcar-core.c
@@ -131,9 +131,13 @@ static int rvin_group_link_notify(struct media_link *link, u32 flags,
!is_media_entity_v4l2_video_device(link->sink->entity))
return 0;
- /* If any entity is in use don't allow link changes. */
+ /*
+ * Don't allow link changes if any entity in the graph is
+ * streaming, because modifying the CHSEL register fields
+ * can disrupt running streams.
+ */
media_device_for_each_entity(entity, &group->mdev)
- if (entity->use_count)
+ if (entity->stream_count)
return -EBUSY;
mutex_lock(&group->lock);
--
2.17.1
Hi Steve,
Thanks for your patch, I think it looks good.
On 2019-01-06 13:20:18 -0800, Steve Longerbeam wrote:
> There is a block of code in rvin_group_link_notify() that loops through
> all entities in the media graph, and prevents enabling a link to a VIN
> node if any entity is in use. This prevents enabling a VIN link even if
> there is an in-use entity somewhere in the graph that is independent of
> the link's pipeline.
>
> For example, the code will prevent enabling a link from the first
> rcar-csi2 receiver to a VIN node even if there is an enabled link
> somewhere far upstream on the second independent rcar-csi2 receiver
> pipeline.
>
> If this code is meant to prevent modifying a link if any entity in the
> graph is actively involved in streaming (because modifying the CHSEL
> register fields can disrupt any/all running streams), then the entities
> stream counts should be checked rather than the use counts.
>
> (There is already such a check in __media_entity_setup_link() that verifies
> the stream_count of the link's source and sink entities are both zero,
> but that is insufficient, since there should be no running streams in
> the entire graph).
>
> Modify the media_device_for_each_entity() loop to check the entity
> stream_count instead of the use_count, and elaborate on the comment.
> VIN node links can now be enabled even if there are other independent
> in-use entities that are not streaming.
>
> Fixes: c0cc5aef31 ("media: rcar-vin: add link notify for Gen3")
>
> Signed-off-by: Steve Longerbeam <[email protected]>
Reviewed-by: Niklas S?derlund <[email protected]>
> ---
> Changes in v2:
> - bring back the media_device_for_each_entity() loop but check the
> stream_count not the use_count.
> ---
> drivers/media/platform/rcar-vin/rcar-core.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/media/platform/rcar-vin/rcar-core.c b/drivers/media/platform/rcar-vin/rcar-core.c
> index f0719ce24b97..6dd6b11c1b2b 100644
> --- a/drivers/media/platform/rcar-vin/rcar-core.c
> +++ b/drivers/media/platform/rcar-vin/rcar-core.c
> @@ -131,9 +131,13 @@ static int rvin_group_link_notify(struct media_link *link, u32 flags,
> !is_media_entity_v4l2_video_device(link->sink->entity))
> return 0;
>
> - /* If any entity is in use don't allow link changes. */
> + /*
> + * Don't allow link changes if any entity in the graph is
> + * streaming, because modifying the CHSEL register fields
> + * can disrupt running streams.
> + */
> media_device_for_each_entity(entity, &group->mdev)
> - if (entity->use_count)
> + if (entity->stream_count)
> return -EBUSY;
>
> mutex_lock(&group->lock);
> --
> 2.17.1
>
--
Regards,
Niklas S?derlund
On 1/9/19 2:40 PM, Niklas Söderlund wrote:
> Hi Steve,
>
> Thanks for your patch, I think it looks good.
Thanks for the Ack! I'm not real familiar with the RFC patch process.
Should this be submitted again with RFC stripped from the subject line?
Steve
> On 2019-01-06 13:20:18 -0800, Steve Longerbeam wrote:
>> There is a block of code in rvin_group_link_notify() that loops through
>> all entities in the media graph, and prevents enabling a link to a VIN
>> node if any entity is in use. This prevents enabling a VIN link even if
>> there is an in-use entity somewhere in the graph that is independent of
>> the link's pipeline.
>>
>> For example, the code will prevent enabling a link from the first
>> rcar-csi2 receiver to a VIN node even if there is an enabled link
>> somewhere far upstream on the second independent rcar-csi2 receiver
>> pipeline.
>>
>> If this code is meant to prevent modifying a link if any entity in the
>> graph is actively involved in streaming (because modifying the CHSEL
>> register fields can disrupt any/all running streams), then the entities
>> stream counts should be checked rather than the use counts.
>>
>> (There is already such a check in __media_entity_setup_link() that verifies
>> the stream_count of the link's source and sink entities are both zero,
>> but that is insufficient, since there should be no running streams in
>> the entire graph).
>>
>> Modify the media_device_for_each_entity() loop to check the entity
>> stream_count instead of the use_count, and elaborate on the comment.
>> VIN node links can now be enabled even if there are other independent
>> in-use entities that are not streaming.
>>
>> Fixes: c0cc5aef31 ("media: rcar-vin: add link notify for Gen3")
>>
>> Signed-off-by: Steve Longerbeam <[email protected]>
> Reviewed-by: Niklas Söderlund <[email protected]>
>
>> ---
>> Changes in v2:
>> - bring back the media_device_for_each_entity() loop but check the
>> stream_count not the use_count.
>> ---
>> drivers/media/platform/rcar-vin/rcar-core.c | 8 ++++++--
>> 1 file changed, 6 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/media/platform/rcar-vin/rcar-core.c b/drivers/media/platform/rcar-vin/rcar-core.c
>> index f0719ce24b97..6dd6b11c1b2b 100644
>> --- a/drivers/media/platform/rcar-vin/rcar-core.c
>> +++ b/drivers/media/platform/rcar-vin/rcar-core.c
>> @@ -131,9 +131,13 @@ static int rvin_group_link_notify(struct media_link *link, u32 flags,
>> !is_media_entity_v4l2_video_device(link->sink->entity))
>> return 0;
>>
>> - /* If any entity is in use don't allow link changes. */
>> + /*
>> + * Don't allow link changes if any entity in the graph is
>> + * streaming, because modifying the CHSEL register fields
>> + * can disrupt running streams.
>> + */
>> media_device_for_each_entity(entity, &group->mdev)
>> - if (entity->use_count)
>> + if (entity->stream_count)
>> return -EBUSY;
>>
>> mutex_lock(&group->lock);
>> --
>> 2.17.1
>>
On 1/9/19 5:19 PM, Steve Longerbeam wrote:
>
>
> On 1/9/19 2:40 PM, Niklas Söderlund wrote:
>> Hi Steve,
>>
>> Thanks for your patch, I think it looks good.
>
> Thanks for the Ack! I'm not real familiar with the RFC patch process.
> Should this be submitted again with RFC stripped from the subject line?
I've been told there isn't really a process for RFC patch submission. I
will re-submit and strip off the RFC and add your Reviewed-by.
Steve
>
>
>> On 2019-01-06 13:20:18 -0800, Steve Longerbeam wrote:
>>> There is a block of code in rvin_group_link_notify() that loops through
>>> all entities in the media graph, and prevents enabling a link to a VIN
>>> node if any entity is in use. This prevents enabling a VIN link even if
>>> there is an in-use entity somewhere in the graph that is independent of
>>> the link's pipeline.
>>>
>>> For example, the code will prevent enabling a link from the first
>>> rcar-csi2 receiver to a VIN node even if there is an enabled link
>>> somewhere far upstream on the second independent rcar-csi2 receiver
>>> pipeline.
>>>
>>> If this code is meant to prevent modifying a link if any entity in the
>>> graph is actively involved in streaming (because modifying the CHSEL
>>> register fields can disrupt any/all running streams), then the entities
>>> stream counts should be checked rather than the use counts.
>>>
>>> (There is already such a check in __media_entity_setup_link() that
>>> verifies
>>> the stream_count of the link's source and sink entities are both zero,
>>> but that is insufficient, since there should be no running streams in
>>> the entire graph).
>>>
>>> Modify the media_device_for_each_entity() loop to check the entity
>>> stream_count instead of the use_count, and elaborate on the comment.
>>> VIN node links can now be enabled even if there are other independent
>>> in-use entities that are not streaming.
>>>
>>> Fixes: c0cc5aef31 ("media: rcar-vin: add link notify for Gen3")
>>>
>>> Signed-off-by: Steve Longerbeam <[email protected]>
>> Reviewed-by: Niklas Söderlund <[email protected]>
>>
>>> ---
>>> Changes in v2:
>>> - bring back the media_device_for_each_entity() loop but check the
>>> stream_count not the use_count.
>>> ---
>>> drivers/media/platform/rcar-vin/rcar-core.c | 8 ++++++--
>>> 1 file changed, 6 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/media/platform/rcar-vin/rcar-core.c
>>> b/drivers/media/platform/rcar-vin/rcar-core.c
>>> index f0719ce24b97..6dd6b11c1b2b 100644
>>> --- a/drivers/media/platform/rcar-vin/rcar-core.c
>>> +++ b/drivers/media/platform/rcar-vin/rcar-core.c
>>> @@ -131,9 +131,13 @@ static int rvin_group_link_notify(struct
>>> media_link *link, u32 flags,
>>> !is_media_entity_v4l2_video_device(link->sink->entity))
>>> return 0;
>>> - /* If any entity is in use don't allow link changes. */
>>> + /*
>>> + * Don't allow link changes if any entity in the graph is
>>> + * streaming, because modifying the CHSEL register fields
>>> + * can disrupt running streams.
>>> + */
>>> media_device_for_each_entity(entity, &group->mdev)
>>> - if (entity->use_count)
>>> + if (entity->stream_count)
>>> return -EBUSY;
>>> mutex_lock(&group->lock);
>>> --
>>> 2.17.1
>>>
>