Re: [PATCH v3 4/6] usb: gadget: f_fs: add a device reference of usb_gadget->dev

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Wed, Mar 29, 2023 at 03:00:54PM +0800, Linyu Yuan wrote:
> 
> On 3/29/2023 2:53 PM, Greg Kroah-Hartman wrote:
> > On Mon, Mar 27, 2023 at 06:12:18PM +0800, Linyu Yuan wrote:
> > > It is known that dev_vdbg() macro can accept NULL or non-NULL dev pointer.
> > > 
> > > Add a struct device *dev member in struct ffs_data, set it to NULL before
> > > binding or after unbinding to a usb_gadget, set it reference of usb_gadget
> > > ->dev when bind success.
> > > 
> > > Then it can help replace private pr_vdebug() to dev_vdbg() consistently.
> > > 
> > > Signed-off-by: Linyu Yuan <quic_linyyuan@quicinc.com>
> > > ---
> > > v3: new patch in this version
> > > 
> > >   drivers/usb/gadget/function/f_fs.c | 3 +++
> > >   drivers/usb/gadget/function/u_fs.h | 1 +
> > >   2 files changed, 4 insertions(+)
> > > 
> > > diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
> > > index a4051c8..25461f1 100644
> > > --- a/drivers/usb/gadget/function/f_fs.c
> > > +++ b/drivers/usb/gadget/function/f_fs.c
> > > @@ -1722,6 +1722,7 @@ static struct ffs_data *ffs_data_new(const char *dev_name)
> > >   		return NULL;
> > >   	}
> > > +	ffs->dev = NULL;
> > >   	refcount_set(&ffs->ref, 1);
> > >   	atomic_set(&ffs->opened, 0);
> > >   	ffs->state = FFS_READ_DESCRIPTORS;
> > > @@ -1831,6 +1832,7 @@ static int functionfs_bind(struct ffs_data *ffs, struct usb_composite_dev *cdev)
> > >   	}
> > >   	ffs->gadget = cdev->gadget;
> > > +	ffs->dev = &cdev->gadget->dev;
> > >   	ffs_data_get(ffs);
> > >   	return 0;
> > >   }
> > > @@ -1843,6 +1845,7 @@ static void functionfs_unbind(struct ffs_data *ffs)
> > >   		mutex_lock(&ffs->mutex);
> > >   		usb_ep_free_request(ffs->gadget->ep0, ffs->ep0req);
> > >   		ffs->ep0req = NULL;
> > > +		ffs->dev = NULL;
> > >   		ffs->gadget = NULL;
> > >   		clear_bit(FFS_FL_BOUND, &ffs->flags);
> > >   		mutex_unlock(&ffs->mutex);
> > > diff --git a/drivers/usb/gadget/function/u_fs.h b/drivers/usb/gadget/function/u_fs.h
> > > index 4b3365f..c5f6167 100644
> > > --- a/drivers/usb/gadget/function/u_fs.h
> > > +++ b/drivers/usb/gadget/function/u_fs.h
> > > @@ -146,6 +146,7 @@ enum ffs_setup_state {
> > >   struct ffs_data {
> > >   	struct usb_gadget		*gadget;
> > > +	struct device			*dev;
> > No, sorry, this is not correct.
> > 
> > You already have a struct device right there in the struct usb_gadget.
> > Use that one instead, as you are just setting this pointer to the same
> > value (see above where you set it.)
> 
> 
> just want to use consistent dev_(v)dbg() related macro, to avoid reference 
> usb_gadget->dev
> 
> when usb_gadget is NULL.

When will usb_gadget be NULL when you want to print out logging
messages?  You shouldn't be printing out anything during that time
anyway, right?

thanks,

greg k-h