urma: uburma: return a negative errno when the ubcore device is gone · Pull Request !1127 · OpenCloudOS/OpenCloudOS-Kernel

## Problem

`uburma_open()` reports a missing ubcore device with `ret = EIO`. `EIO` is
positive, so the file operation returns `5` instead of an error code.

The VFS requires `->open()` to return a negative errno. `do_dentry_open()`
passes the positive value through `WARN_ON_ONCE()` in `cleanup_all` and
substitutes `-EINVAL`, so opening the character device while the ubcore device
has already been detached (`uburma_remove_dev()` clears `ubu_dev->ubc_dev`)
both emits a kernel warning and reports the wrong errno to userspace.

## Fix

Negate the errno. Every other error return in this file and in the surrounding
URMA code already uses a negative errno.

## Verification

- `scripts/checkpatch.pl --no-signoff --strict`: 0 errors, 0 warnings.
- arm64 build (`CONFIG_UB=y` + `CONFIG_UB_URMA=y`, target `drivers/ub/urma/uburma/`, Bootlin aarch64 gcc 15.3.0, `W=1`): baseline and patched trees both build with exit 0 and no warnings, all 8 objects force-recompiled in both cases.
- Not run: runtime regression. No UB hardware is available in the development environment; the change only affects the errno of an already failing open.

类型	指派人员	状态
审查	zoucao Huang Cun Jianping Liu	已完成 (0/0人)
测试	Jianping Liu	已完成 (0/0人)

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