A few comments:
> + dev_err(port->dev, "PPS support disabled due port \"%s\" is "
> + "in polling mode\n",
I think "because" instead of "due" is closer to standard English.
> + printk(KERN_ERR "pps: %s: too much PPS sources in the system\n",
> + info->name);
Similarly should be "many" instead of "much".
> + /* Get new ID for the new PPS source */
> + if (idr_pre_get(&pps_idr, GFP_KERNEL) == 0) {
> + err = -ENOMEM;
> + goto kfree_pps;
> + }
> +
> + spin_lock_irq(&idr_lock);
> + err = idr_get_new(&pps_idr, pps, &id);
> + spin_unlock_irq(&idr_lock);
> +
> + if (err < 0)
> + goto kfree_pps;
You usually can handle idr_get_new() returning -EAGAIN by jumping back
to the idr_pre_get(), to handle someone else coming in and stealing
the memory you just preallocated. In this case it may not matter
since it's pretty unlikely that a lot of contexts are using the idr at
the same time. But anyway...
> +void pps_unregister_source(int source)
> ...
> + wait_event(pps->usage_queue, atomic_read(&pps->usage) == 0);
> +
> + pps_sysfs_remove_source_entry(pps);
> + pps_unregister_cdev(pps);
> + kfree(pps);
This reference counting looks dubious to me... later on in the code
you have:
> +static int pps_cdev_open(struct inode *inode, struct file *file)
> +{
> + struct pps_device *pps = container_of(inode->i_cdev,
> + struct pps_device, cdev);
> +
> + /* Lock the PPS source against (possible) deregistration */
> + atomic_inc(&pps->usage);
with no locking, so I see no reason why the atomic_inc() couldn't
happen right after the wait_event() sees a count of 0 and lets the
deregistration continue. Which would lead to use-after-free.
- R.
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