Fix vcam_enum_framesizes to enumerate all sizes when scaling is enabled

[davidzwei]

When scaling is enabled, vcam_enum_framesizes only returned one frame size because the index guard was never updated after the branch was changed. The original else block also became unreachable dead code.

Fix by removing the dead code and enumerating vcam_sizes[] by index.

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Summary by cubic

Fixes vcam_enum_framesizes to return all discrete frame sizes instead of only the current output size when scaling is enabled. Removes redundant branches and adds proper bounds checking.

• Bug Fixes
  • Iterates vcam_sizes[fsize->index] with >= ARRAY_SIZE(vcam_sizes) guard to enumerate all discrete sizes.
  • Removes the conv_res_on duplicate path and the unreachable stepwise branch.

^{Written for commit ca444a0. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 1 file

_{Re-trigger cubic}

[jserv]

Read https://cbea.ms/git-commit/ carefully and enforce the rules.

[jserv]

Provide test cases to reproduce.

[davidzwei]

I've modified my commit message.

[davidzwei]

test case to reproduce:

This test case verifies that VIDIOC_ENUM_FRAMESIZES returns all supported frame sizes when scaling is enabled. Before the fix, only the first size was returned due to an incorrect index guard in vcam_enum_framesizes.

sudo insmod vcam.ko allow_scaling=1
sudo ./vcam-util -l        # find the device node, e.g. /dev/video0
v4l2-ctl -d /dev/video0 --list-framesizes=RGB3  # replace with actual device node
sudo rmmod vcam

output before fix:

Size: Discrete 640x480

output after fix:

Size: Discrete 480x360
Size: Discrete 640x480
Size: Discrete 1280x720

[jserv]

Thank @davidzwei for contributing!