Re: [PATCH v2 2/2] usb: roles: don't get/set_role() when usb_role_switch is unregistered

[Greg KH <gregkh@linuxfoundation.org>]

On Wed, Jan 24, 2024 at 02:45:54PM +0800, Xu Yang wrote:
> There is a possibility that usb_role_switch device is unregistered before
> the user put usb_role_switch. In this case, the user may still want to
> get/set_role() since the user can't sense the changes of usb_role_switch.
> 
> This will add a flag to show if usb_role_switch is already registered and
> avoid unwanted behaviors.
> 
> Signed-off-by: Xu Yang <xu.yang_2@nxp.com>
> 
> ---
> Changes in v2:
>  - new patch during test patch 1
>  - add registered flag
> ---
>  drivers/usb/roles/class.c | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/roles/class.c b/drivers/usb/roles/class.c
> index 2bad038fb9ad..70165dd86b5d 100644
> --- a/drivers/usb/roles/class.c
> +++ b/drivers/usb/roles/class.c
> @@ -23,6 +23,7 @@ struct usb_role_switch {
>  	struct mutex lock; /* device lock*/
>  	struct module *module; /* the module this device depends on */
>  	enum usb_role role;
> +	bool registered;
>  
>  	/* From descriptor */
>  	struct device *usb2_port;
> @@ -49,6 +50,9 @@ int usb_role_switch_set_role(struct usb_role_switch *sw, enum usb_role role)
>  	if (IS_ERR_OR_NULL(sw))
>  		return 0;
>  
> +	if (!sw->registered)
> +		return -EOPNOTSUPP;

What's to prevent this from changing right after you check it?

And why is this patch not cc: stable and have a fixes tag if it resolves
a real issue for people?

thanks,

greg k-h