[PATCH v2 0/6] Support getting default values from any control

From: Ricardo Ribalda Delgado
Date: Thu Oct 29 2015 - 06:10:43 EST

Integer controls provide a way to get their default/initial value, but
any other control (p_u32, p_u8.....) provide no other way to get the
initial value than unloading the module and loading it back.

*What is the actual problem?
I have a custom control with WIDTH integer values. Every value
represents the calibrated FPN (fixed pattern noise) correction value for that
-Application A changes the FPN correction value
-Application B wants to restore the calibrated value but it cant :(

*What is the proposed solution?

(Kudos to Hans Verkuil!!!)

The key change is in struct v4l2_ext_controls where the __u32 ctrl_class field
is changed to:

union {
__u32 ctrl_class;
__u32 which;

And two new defines are added:

#define V4L2_CTRL_WHICH_DEF_VAL 0x0f000000

The 'which' field tells you which controls are get/set/tried.

V4L2_CTRL_WHICH_CUR_VAL: the current value of the controls
V4L2_CTRL_WHICH_DEF_VAL: the default value of the controls
V4L2_CTRL_CLASS_*: the current value of the controls belonging to the specified class.
Note: this is deprecated usage and is only there for backwards compatibility.
Which is also why I don't think there is a need to add V4L2_CTRL_WHICH_
aliases for these defines.

I have posted a copy of my working tree to:


Changelog v2 (compared to Support getting default values from any control

Rebase to latest version
Remove saa7164-* patches (Hans already ported them to v4l2-ctrl)
Update doc dates

Suggested by Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>:

Fixes for the uvc implementation (error in lock handling) (Thanks!)

Changelog v1 (compared to v5 of New ioct VIDIOC_G_DEF_EXT_CTRLS):

Suggested by Hans Verkuil <hverkuil@xxxxxxxxx>:

Replace ioctl implementation with a new union on the struct v4l2_ext_controls

Ricardo Ribalda Delgado (6):
videodev2.h: Extend struct v4l2_ext_controls
media/core: Replace ctrl_class with which
media/v4l2-core: struct struct v4l2_ext_controls param which
usb/uvc: Support for V4L2_CTRL_WHICH_DEF_VAL
media/usb/pvrusb2: Support for V4L2_CTRL_WHICH_DEF_VAL
Docbook: media: Document changes on struct v4l2_ext_controls

Documentation/DocBook/media/v4l/v4l2.xml | 10 ++++
.../DocBook/media/v4l/vidioc-g-ext-ctrls.xml | 28 +++++++++--
drivers/media/platform/s5p-mfc/s5p_mfc_dec.c | 2 +-
drivers/media/platform/s5p-mfc/s5p_mfc_enc.c | 2 +-
drivers/media/usb/pvrusb2/pvrusb2-v4l2.c | 16 ++++++-
drivers/media/usb/uvc/uvc_v4l2.c | 20 ++++++++
drivers/media/v4l2-core/v4l2-compat-ioctl32.c | 6 +--
drivers/media/v4l2-core/v4l2-ctrls.c | 54 ++++++++++++++++------
drivers/media/v4l2-core/v4l2-ioctl.c | 14 +++---
include/uapi/linux/videodev2.h | 12 ++++-
10 files changed, 131 insertions(+), 33 deletions(-)


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