[bug report] mux: Add helper functions for getting optional and selected mux-state

Hello Josua Mayer,

Commit 993bcaf32c49 ("mux: Add helper functions for getting optional
and selected mux-state") from Feb 26, 2026 (linux-next), leads to the
following Smatch static checker warning:

	drivers/mux/core.c:640 mux_control_get()
	warn: 'mux' is an error pointer or valid

drivers/mux/core.c
    630  * mux_control_get() - Get the mux-control for a device.
    631  * @dev: The device that needs a mux-control.
    632  * @mux_name: The name identifying the mux-control.
    633  *
    634  * Return: A pointer to the mux-control, or an ERR_PTR with a negative errno.
    635  */
    636 struct mux_control *mux_control_get(struct device *dev, const char *mux_name)
    637 {
    638         struct mux_control *mux = mux_get(dev, mux_name, NULL, false);

mux_get() can only return NULL if optional is true.

    639 
--> 640         if (!mux)

this should be if (IS_ERR(mux)) {

    641                 return ERR_PTR(-ENOENT);
    642 
    643         return mux;
    644 }

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regards,
dan carpenter