At least one V4L2 device reports a menu control when queried with
QUERYCTRL yet does not report supporting a single value in its legal
range when queried with QUERYMENU. Such devices are arguably
ill-behaved, but the Linux UVC driver takes no special care to ignore
such pathological controls, so we have to do it ourselves.
Without this patch, a menu control with no valid values would cause
v4l2_control_changed to go into an infinite loop, since every S_CTRL
request on such pathological control properties would always fail,
triggering an additional modification event. By ignoring these
properties altogether, we avoid that problem, and the user benefits by
not having the UI cluttered by a confusing and useless menu control.
add_control_property() was previously static inline bool, but did not
return a value and failed to build on FreeBSD-CURRENT with Clang 10.0,
with:
error: non-void function 'add_control_property' should return a value
Previous fix in #2547 altered id before they were handed off to
callbacks and v4l2 wont strip its own flags from ids resulting in
invalid ids in the ioctl.
Instead add cleanup section and jump all branches there before looping.
(Jim edit: I'm changing this entire function so that it isn't horrible.)
v4l2_ioctl will clear the V4L2_CTRL_FLAG_NEXT_CTRL flag resulting in
infinite loops for any driver that reported readonly, disabled, or
volitile controls.
As currently all 64bit Linux platforms are respecting LP64
data model and most 32bit platforms are respecting ILP32, we
don't have to discuss pointer size case by case. LP64 is effective
enough to tell pointer size.
This fixes build for armhf and powerpc.
Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
