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    SubjectRe: [PATCH v11 3/4] add FPGA manager core
    On Wed, Sep 23, 2015 at 12:10:13PM -0500, atull wrote:
    > On Tue, 22 Sep 2015, Josh Cartwright wrote:
    [..]
    > > > +struct fpga_manager *of_fpga_mgr_get(struct device_node *node)
    > > > +{
    > > > + struct fpga_manager *mgr;
    > > > + struct device *dev;
    > > > +
    > > > + if (!node)
    > > > + return ERR_PTR(-EINVAL);
    > > > +
    > > > + dev = class_find_device(fpga_mgr_class, NULL, node,
    > > > + fpga_mgr_of_node_match);
    > > > + if (!dev)
    > > > + return ERR_PTR(-ENODEV);
    > > > +
    > > > + mgr = to_fpga_manager(dev);
    > > > + put_device(dev);
    > >
    > > Who's ensuring the FPGA manager device's lifetime between _get and _put?
    >
    > Well... get_device and put_device are not sufficient?

    Sorry if I was too opaque.

    You've just put_device()'d the only reference to the device you had
    here, so nothing is preventing from the device from being ripped away
    while it's being used.

    You should remove the put_device() call here, and add a corresponding
    put_device() in fpga_mgr_put().

    The module refcounting is also a bit strange, as you are
    acquiring/releasing a reference to THIS_MODULE, but you also should care
    about the lower-level driver's module refcount.

    [..]
    > > > + dt_label = of_get_property(mgr->dev.of_node, "label", NULL);
    > > > + if (dt_label)
    > > > + ret = dev_set_name(&mgr->dev, "%s", dt_label);
    > > > + else
    > > > + ret = dev_set_name(&mgr->dev, "fpga%d", id);
    > >
    > > I'm wondering if an alias {} node is better for this.
    >
    > I could look into that. Is there an example of that you particularly
    > like for this?

    Look at i2c's usage of the of_alias_*() functions.

    Josh
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