On 27/09/2021 04:45, Laurent Pinchart wrote:
Hi Tomi,
Thank you for the patch.
On Mon, Aug 30, 2021 at 02:00:46PM +0300, Tomi Valkeinen wrote:
All suitable subdev ops are now passed either the TRY or the ACTIVE
state by the v4l2 core. However, other subdrivers can still call the ops
passing NULL as the state, implying the active case.
Thus all subdev drivers supporting active state need to handle the NULL
state case.
Do they ? Can't we mandate that the callers pass the correct state ? Do
you think that would make the transition too difficult ?
That would limit the use of the new drivers. E.g. the sensor driver I'm
using works fine with CAL & co. without handling the NULL, but then the
sensor driver couldn't be used with "old" drivers.
The way I understand the issue, this would only be needed to facilitate
the transition. Is there a reason why the drivers you've ported (CAL &
co.) use v4l2_subdev_validate_and_lock_state() after completing the
transition, or is the correct state always passed by the caller ?
The drivers I'm using only call non-state-aware ops in the other
subdevs, so they should work fine without validate.
I think it's safer to just use the validate versions for now. They're
trivial to convert to non-validate versions later.
We could just do the validate implicitly while locking the state, but it
would make the code a bit odd:
state = v4l2_subdev_lock_state(state);
After the transition we want to do just:
v4l2_subdev_lock_state(state);
Or we could do v4l2_subdev_lock_state() with a macro, which changes the
state variable, but... I think I'd rather have it clear and obvious with
v4l2_subdev_validate_and_lock_state().
Additionally, the subdev drivers usually need to lock the
state.
Add two helper functions to easen the transition to centrally managed
ACTIVE state. v4l2_subdev_validate_state() ensures that the state is not
NULL, and v4l2_subdev_validate_and_lock_state() does the same and
additionally locks the state.
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@xxxxxxxxxxxxxxxx>
---
include/media/v4l2-subdev.h | 41 +++++++++++++++++++++++++++++++++++++
1 file changed, 41 insertions(+)
diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
index 52a725281b23..2290b5025fc0 100644
--- a/include/media/v4l2-subdev.h
+++ b/include/media/v4l2-subdev.h
@@ -1307,4 +1307,45 @@ void v4l2_subdev_lock_state(struct v4l2_subdev_state *state);
*/
void v4l2_subdev_unlock_state(struct v4l2_subdev_state *state);
+/**
+ * v4l2_subdev_validate_state() - Gets the TRY or ACTIVE subdev state
+ * @sd: subdevice
+ * @state: subdevice state as passed to the subdev op
+ *
+ * Subdev ops used to be sometimes called with NULL as the state for ACTIVE
+ * case. Even if the v4l2 core now passes proper state for both TRY and
+ * ACTIVE cases, a subdev driver may call an op in another subdev driver,
+ * passing NULL.
+ *
+ * This function can be used as a helper to get the state also for the ACTIVE
+ * case. The subdev driver that supports ACTIVE state can use this function
+ * as the first thing in its ops, ensuring that the state variable contains
+ * either the TRY or ACTIVE state.
+ */
+static inline struct v4l2_subdev_state *
+v4l2_subdev_validate_state(struct v4l2_subdev *sd,
+ struct v4l2_subdev_state *state)
+{
+ return state ? state : sd->state;
+}
This doesn't seem to be used by the drivers you've ported, or by the
R-Car and GMSL patches from Jacopo. Do we need this function ?
Probably not. If you need to validate, you most likely will lock the
state right afterwards, so v4l2_subdev_validate_and_lock_state should be
enough.
Tomi
