should failed calls to device_register() always call put_device()?

[Belisko Marek]

Hi Robert,

On Sat, May 28, 2011 at 5:15 PM, Robert P. J. Day <rpjday at crashcourse.ca> wrote:
>
>  from drivers/base/core.c, we have the fairly unambiguous advice:
>
> * NOTE: _Never_ directly free @dev after calling this function, even
> * if it returned an error! Always use put_device() to give up the
> * reference initialized in this function instead.
> */
> int device_register(struct device *dev)
> {
>        device_initialize(dev);
>        return device_add(dev);
> }
>
>  and yet, there appears to be driver code that does exactly that,
> such as this snippet from drivers/w1/w1_int.c (line 86):
>
>        ... snip ...
>        err = device_register(&dev->dev);
>        if (err) {
>                printk(KERN_ERR "Failed to register master device. err=%d\n", err);
>                memset(dev, 0, sizeof(struct w1_master));
>                kfree(dev);
>                dev = NULL;
>        }
Free is for allocated dev not for struct device so it is OK. IMO thi
snippet should look like:
err = device_register(&dev->dev);
if (err) {
    printk(KERN_ERR "Failed to register master device. err=%d\n", err);
    put_device(&dev->dev);
    memset(dev, 0, sizeof(struct w1_master));
    kfree(dev);
    dev = NULL;
}

>
>        return dev;
>
>  isn't the above doing just that -- directly freeing the dev
> structure without first calling put_device()?  or am i misreading
> something?
>
> rday
>
> --
>
> ========================================================================
> Robert P. J. Day                                 Ottawa, Ontario, CANADA
>                        http://crashcourse.ca
>
> Twitter:                                       http://twitter.com/rpjday
> LinkedIn:                               http://ca.linkedin.com/in/rpjday
> ========================================================================
>
>
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regards,

marek

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