[libcamera-devel] [PATCH v2 06/19] py: Add CameraManager.read_event()

[Laurent Pinchart]

Hi Tomi,

On Fri, May 27, 2022 at 09:00:44AM +0300, Tomi Valkeinen wrote:
> On 26/05/2022 18:27, Laurent Pinchart wrote:
> > On Tue, May 24, 2022 at 02:45:57PM +0300, Tomi Valkeinen wrote:
> >> Add CameraManager.read_event() so that the user does not need to call
> >> os.read().
> >>
> >> We use eventfd, and we must always read 8 bytes. Hiding that inside
> >> read_event() makes sense.
> >>
> >> Signed-off-by: Tomi Valkeinen <tomi.valkeinen at ideasonboard.com>
> >> ---
> >>   src/py/cam/cam.py            | 3 +--
> >>   src/py/libcamera/py_main.cpp | 8 ++++++++
> >>   test/py/unittests.py         | 3 +--
> >>   3 files changed, 10 insertions(+), 4 deletions(-)
> >>
> >> diff --git a/src/py/cam/cam.py b/src/py/cam/cam.py
> >> index e2bc78da..66df18bf 100755
> >> --- a/src/py/cam/cam.py
> >> +++ b/src/py/cam/cam.py
> >> @@ -9,7 +9,6 @@
> >>   import argparse
> >>   import binascii
> >>   import libcamera as libcam
> >> -import os
> >>   import sys
> >>   import traceback
> >>   
> >> @@ -294,7 +293,7 @@ def event_handler(state):
> >>           cm = state['cm']
> >>           contexts = state['contexts']
> >>   
> >> -        os.read(cm.efd, 8)
> >> +        cm.read_event()
> >>   
> >>           reqs = cm.get_ready_requests()
> > 
> > Would it make sense to read the event within get_ready_requests() ?
> 
> I thought about these two functions, but this seemed the safest to me. 
> If get_ready_requests() would do read_event(), then you could not call 
> get_ready_requests() unless you knew there is an event waiting, or it 
> would block. Or we could make the fd non-blocking, but I think that's 
> usually the choice of the user, not the library.

Hmmm... I have a feeling we can do better, but I don't know what yet :-)
It doesn't have to be done now.

-- 
Regards,

Laurent Pinchart