libcamera: Rename "shutter speed" to "exposure time"

The terms "shutter" and "shutter speed" are used through libcamera to
mean "exposure time". This is confusing, both due to "speed" being used
as "time" while it should be the inverse (i.e. a maximum speed should
correspond to the minimum time), and due to "shutter speed" and
"exposure time" being used in different places with the same meaning.

To improve clarity of the code base and the documentation, use "exposure
time" consistently to replace "shutter speed".

This rename highlighted another vocabulary issue in libcamera. The
ExposureModeHelper::splitExposure() function used to document that it
splits "exposure time into shutter time and gain". It has been reworded
to "split exposure into exposure time and gain". That is not entirely
satisfactory, as "exposure" has a defined meaning in photography (see
https://en.wikipedia.org/wiki/Exposure_(photography)) that is not
expressed as a duration. This issue if left to be addressed separately.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Naushir Patuck <naush@raspberrypi.com>
Acked-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

1 files changed, 3 insertions, 3 deletions

diff --git a/src/ipa/rpi/controller/camera_mode.h b/src/ipa/rpi/controller/camera_mode.h
index 4fdb5b85..61162b32 100644
--- a/src/ipa/rpi/controller/camera_mode.h
+++ b/src/ipa/rpi/controller/camera_mode.h
@@ -50,9 +50,9 @@ struct CameraMode {
 	double sensitivity;
 	/* pixel clock rate */
 	uint64_t pixelRate;
-	/* Mode specific shutter speed limits */
-	libcamera::utils::Duration minShutter;
-	libcamera::utils::Duration maxShutter;
+	/* Mode specific exposure time limits */
+	libcamera::utils::Duration minExposureTime;
+	libcamera::utils::Duration maxExposureTime;
 	/* Mode specific analogue gain limits */
 	double minAnalogueGain;
 	double maxAnalogueGain;