This series goal is avoiding drivers from having ad-hoc code
to call .device_run in non-atomic context. Currently, .device_run
can be called via v4l2_m2m_job_finish(), potentially running
in interrupt context.
This is needed for the upcoming Request API, where drivers typically
require .device_run to be called in non-atomic context for
v4l2_ctrl_request_setup() calls.
The solution is quite simple, instead of drivers having a threaded interrupt
or similar, the mem2mem core has a per-context worker that is scheduled
by v4l2_m2m_job_finish.
This change allows v4l2_m2m_job_finish() to be called in interrupt
context, separating .device_run and v4l2_m2m_job_finish() contexts.
It's worth mentioning that v4l2_m2m_cancel_job() doesn't need
to flush or cancel the new worker, because the job_spinlock
synchronizes both and also because the core prevents simultaneous
jobs. Either v4l2_m2m_cancel_job() will wait for the worker, or the
worker will be unable to run a new job.
Paul, Maxime: This should avoid the threaded interrupt in the Cedrus
driver. Please, take a look and let me know how it goes.
Patches are based on v4.18-rc4 plus:
c1dbb540e35e "v4l2-mem2mem: Simplify exiting the function in
v4l2_m2m_try_schedule"
be3d3b78573b "media: mem2mem: Remove excessive try_run call"
Ezequiel Garcia (2):
v4l2-core: Simplify v4l2_m2m_try_{schedule,run}
v4l2-mem2mem: Avoid calling .device_run in v4l2_m2m_job_finish
drivers/media/v4l2-core/v4l2-mem2mem.c | 58 ++++++++++----------------
include/media/v4l2-mem2mem.h | 2 +
2 files changed, 25 insertions(+), 35 deletions(-)
--
2.18.0.rc2
