Re: [EXT] Re: [PATCH] usb: roles: try to get/put all relevant modules

[Heikki Krogerus <heikki.krogerus@linux.intel.com>]

On Fri, Jan 19, 2024 at 08:18:51AM +0000, Xu Yang wrote:
> Hi,
> 
> > 
> > On Thu, Jan 18, 2024 at 03:52:52PM +0000, Xu Yang wrote:
> > > I've tried your suggestion and it appears to be working fine. Now I'm not sure if
> > > the module get/put parts should be removed or to fix the NULL pointer issue. I'm
> > > working on this issue, so I have time to fix it. I think if first way is taken, the status
> > > of usb_role_switch device should be updated when it's registered/unregisterd. Or
> > > other issues will occur since the user doesn't know the change of usb_role_switch
> > > device.
> > 
> > These really are questions for Heikki, not me.  Can you at least show us
> > the patch you've been testing?
> 
> I have a simple test based on below changes:
> 
> diff --git a/drivers/usb/roles/class.c b/drivers/usb/roles/class.c
> index ae41578bd014..d55a5d8d4fc4 100644
> --- a/drivers/usb/roles/class.c
> +++ b/drivers/usb/roles/class.c
> @@ -20,6 +20,7 @@ static const struct class role_class = {
>  
>  struct usb_role_switch {
>  	struct device dev;
> +	struct module *module;
>  	struct mutex lock; /* device lock*/
>  	enum usb_role role;
>  
> @@ -135,7 +136,7 @@ struct usb_role_switch *usb_role_switch_get(struct device *dev)
>  						  usb_role_switch_match);
>  
>  	if (!IS_ERR_OR_NULL(sw))
> -		WARN_ON(!try_module_get(sw->dev.parent->driver->owner));
> +		WARN_ON(!try_module_get(sw->module));
>  
>  	return sw;
>  }
> @@ -157,7 +158,7 @@ struct usb_role_switch *fwnode_usb_role_switch_get(struct fwnode_handle *fwnode)
>  		sw = fwnode_connection_find_match(fwnode, "usb-role-switch",
>  						  NULL, usb_role_switch_match);
>  	if (!IS_ERR_OR_NULL(sw))
> -		WARN_ON(!try_module_get(sw->dev.parent->driver->owner));
> +		WARN_ON(!try_module_get(sw->module));
>  
>  	return sw;
>  }
> @@ -172,7 +173,7 @@ EXPORT_SYMBOL_GPL(fwnode_usb_role_switch_get);
>  void usb_role_switch_put(struct usb_role_switch *sw)
>  {
>  	if (!IS_ERR_OR_NULL(sw)) {
> -		module_put(sw->dev.parent->driver->owner);
> +		module_put(sw->module);
>  		put_device(&sw->dev);
>  	}
>  }
> @@ -189,15 +190,18 @@ struct usb_role_switch *
>  usb_role_switch_find_by_fwnode(const struct fwnode_handle *fwnode)
>  {
>  	struct device *dev;
> +	struct usb_role_switch *sw = NULL;
>  
>  	if (!fwnode)
>  		return NULL;
>  
>  	dev = class_find_device_by_fwnode(&role_class, fwnode);
> -	if (dev)
> -		WARN_ON(!try_module_get(dev->parent->driver->owner));
> +	if(dev) {
> +		sw = to_role_switch(dev);
> +		WARN_ON(!try_module_get(sw->module));
> +	}
>  
> -	return dev ? to_role_switch(dev) : NULL;
> +	return sw;
>  }
>  EXPORT_SYMBOL_GPL(usb_role_switch_find_by_fwnode);
>  
> @@ -339,6 +343,7 @@ usb_role_switch_register(struct device *parent,
>  	sw->get = desc->get;
>  
>  	sw->dev.parent = parent;
> +	sw->module = parent->driver->owner;
>  	sw->dev.fwnode = desc->fwnode;
>  	sw->dev.class = &role_class;
>  	sw->dev.type = &usb_role_dev_type;

This looks good to me.

-- 
heikki