Hi Sean,
On Tue, Jan 25, 2022 at 11:53:58AM -0500, Sean Anderson wrote:
> Hi Heikki,
>
> On 1/25/22 4:18 AM, Heikki Krogerus wrote:
> > On Mon, Jan 24, 2022 at 12:33:44PM -0500, Sean Anderson wrote:
> >> of_node_put should always be called on device nodes gotten from
> >> of_get_*. Additionally, it should only be called after there are no
> >> remaining users. To address the first issue, call of_node_put if later
> >> steps in ulpi_register fail. To address the latter, call of_node_put
> >> only after calling device_unregister.
> >
> > This looks like a fix, but you don't have the fix tag.
>
> You're right this should have
>
> Fixes: ef6a7bcfb01c ("usb: ulpi: Support device discovery via DT")
>
> >> Signed-off-by: Sean Anderson <sean.anderson@xxxxxxxx>
> >> ---
> >>
> >> Changes in v2:
> >> - New
> >>
> >> drivers/usb/common/ulpi.c | 10 +++++++---
> >> 1 file changed, 7 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/drivers/usb/common/ulpi.c b/drivers/usb/common/ulpi.c
> >> index 87deb514eb78..c6ba72544f2b 100644
> >> --- a/drivers/usb/common/ulpi.c
> >> +++ b/drivers/usb/common/ulpi.c
> >> @@ -301,11 +301,11 @@ static int ulpi_register(struct device *dev, struct ulpi *ulpi)
> >>
> >> ret = ulpi_read_id(ulpi);
> >> if (ret)
> >> - return ret;
> >> + goto err;
> >>
> >> ret = device_register(&ulpi->dev);
> >> if (ret)
> >> - return ret;
> >> + goto err;
> >
> > I think there is another bug in the code here. Missing put_device().
>
> So what is the correct way to create a device? Shouldn't device_register
> be paired with device_unregister? And from what I can tell,
> device_unregister does not put the of_node.
I think this is best explained in the documentation. Check the "Rule
of thumb is" section (device_register() is really just a wrapper that
can only fail if device_add() fails):
https://docs.kernel.org/driver-api/infrastructure.html?highlight=device_add#c.device_add
So you just want to drop the reference if device_register() fails.
That will make sure ulpi_dev_release() is called also in this case.
> > If you first fix that, you should then be able to call
> > fwnode_handle_put() (instead of of_node_put())
>
> Well, we currently only have a ulpi_of_register, so I don't think we
> will have a fwnode here. But I can use that if you wish.
>
> --Sean
>
> > from
> > ulpi_dev_release(), and that should cover all cases.
> >
> >> root = debugfs_create_dir(dev_name(dev), ULPI_ROOT);
> >> debugfs_create_file("regs", 0444, root, ulpi, &ulpi_regs_ops);
> >> @@ -314,6 +314,10 @@ static int ulpi_register(struct device *dev, struct ulpi *ulpi)
> >> ulpi->id.vendor, ulpi->id.product);
> >>
> >> return 0;
> >> +
> >> +err:
> >> + of_node_put(ulpi->dev.of_node);
> >> + return ret;
> >
> > So no need for that.
> >
> >> }
> >>
> >> /**
> >> @@ -357,8 +361,8 @@ void ulpi_unregister_interface(struct ulpi *ulpi)
> >> {
> >> debugfs_remove_recursive(debugfs_lookup(dev_name(&ulpi->dev),
> >> ULPI_ROOT));
> >> - of_node_put(ulpi->dev.of_node);
> >> device_unregister(&ulpi->dev);
> >> + of_node_put(ulpi->dev.of_node);
> >> }
> >
> > And here you can just remove that of_node_put() call.
Note. Just by calling device_unregister() does not guarantee that
there are no more users left. We can be certain that the last user is
gone only when ulpi_dev_release() is called, so that's the place
where you want to release the fwnode (of_node).
thanks,
--
heikki
