On Thu, Sep 30, 2021 at 10:04:02AM -0500, Bjorn Helgaas wrote:
> On Thu, Sep 30, 2021 at 03:12:45PM +0300, Heikki Krogerus wrote:
> > In quirk_huawei_pcie_sva(), use device_create_managed_software_node()
> > instead of device_add_properties() to set the "dma-can-stall"
> > property.
> >
> > Reviewed-by: Andy Shevchenko <andy.shevchenko@xxxxxxxxx>
> > Acked-by: Zhangfei Gao <zhangfei.gao@xxxxxxxxxx>
> > Signed-off-by: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
> > ---
> > Hi,
> >
> > The commit message now says what Bjorn requested, except I left out
> > the claim that the patch fixes a lifetime issue.
>
> Thanks.
>
> The commit log should help reviewers determine whether the change is
> safe and necessary. So far it doesn't have any hints along that line.
>
> Comparing device_add_properties() [1] and
> device_create_managed_software_node() [2], the only difference in this
> case is that the latter sets "swnode->managed = true". The function
> comment says "managed" means the lifetime of the swnode is tied to the
> lifetime of dev, hence my question about a lifetime issue.
>
> I can see that one reason for this change is to remove the last caller
> of device_add_properties(), so device_add_properties() itself can be
> removed. That's a good reason for wanting to do it, and the commit
> log could mention it.
Fair enough. I need to explain the why as well as the what.
I'll improve the commit message, but just to be clear, the goal is
actually not to get rid of device_add_properties(). It is removed in
the second patch together with device_remove_properties() because
there are simply no more users for that API.
> But it doesn't help me figure out whether it's safe. For that,
> I need to know the effect of setting "managed = true". Obviously
> it means *something*, but I don't know what. It looks like the only
> test is in software_node_notify():
>
> device_del
> device_platform_notify_remove
> software_node_notify_remove
> sysfs_remove_link(dev_name)
> sysfs_remove_link("software_node")
> if (swnode->managed) <--
> set_secondary_fwnode(dev, NULL)
> kobject_put(&swnode->kobj)
> device_remove_properties
> if (is_software_node())
> fwnode_remove_software_node
> kobject_put(&swnode->kobj)
> set_secondary_fwnode(dev, NULL)
>
> I'm not sure what's going on here; it looks like some redundancy with
> multiple calls of kobject_put() and set_secondary_fwnode(). Maybe you
> are in the process of removing device_remove_properties() as well as
> device_add_properties()?
It'll get removed, but that's not the goal. The goal is to get rid of
the call to it in device_del(), so not the function itself. That call
is the problem here as explained in commit 151f6ff78cdf ("software
node: Provide replacement for device_add_properties()").
I'll split the second patch, and first only remove that
device_remove_properties() call from device_del(), and only after
that remove the functions themselves.
thanks,
--
heikki
