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

Josua Mayer
2026-04-19T10:16:43Z

Hi Dan,

Am 10.04.26 um 12:12 schrieb Dan Carpenter:
> 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.

Yes, that is the intended contract. This means function can be simplified:

/**
* mux_control_get() - Get the mux-control for a device.
* @dev: The device that needs a mux-control.
* @mux_name: The name identifying the mux-control.
*
* Return: A pointer to the mux-control, or an ERR_PTR with a negative errno.
*/
struct mux_control *mux_control_get(struct device *dev, const char *mux_name)
{
return mux_get(dev, mux_name, NULL, false);
}
EXPORT_SYMBOL_GPL(mux_control_get);

Is it okay to trust such transitive contracts and not check for NULL
in an exported generic helper function?

>
> 639
> --> 640 if (!mux)
>
> this should be if (IS_ERR(mux)) {
>
> 641 return ERR_PTR(-ENOENT);
No, ENOENT is only the fix for unexpected NULL return,
which must not be propagated to the caller.

Other errors should be returned to the caller unchanged.

> 642
> 643 return mux;
> 644 }
>
> This email is a free service from the Smatch-CI project [smatch.sf.net].
regards
Josua Mayer