On Sat, Feb 11, 2017 at 9:42 PM, Logan Gunthorpe <log...@deltatee.com> wrote: > On 11/02/17 11:58 AM, Dan Williams wrote: >> Also when using an embedded cdev how would you recommend avoiding this >> problem? > > I don't know. Hopefully, Greg has a good idea. But it sounds like a > general problem that a lot of cdev's actually suffer from without > realizing. Perhaps we need a more general solution. Some way for the > cdev to reference its containing structure in a way that it's designed > for such that anyone writing a driver will do the right thing without > needing to dive into the kobjects. >
How about something like the below? I.e. hide the details with a new helper api so that all driver writers need to worry about is the parent device and cdev_del(). This is similar to the device_add_disk() and del_gendisk() pairing that we have for block-device drivers. diff --git a/fs/char_dev.c b/fs/char_dev.c index 3bc97002c86f..4c5d51cdd353 100644 --- a/fs/char_dev.c +++ b/fs/char_dev.c @@ -471,6 +471,12 @@ int cdev_add(struct cdev *p, dev_t dev, unsigned count) return 0; } +int device_add_cdev(struct device *dev, struct cdev *p) +{ + p->kobj.parent = &dev->kobj; + return cdev_add(p, dev->devt, 1); +} + static void cdev_unmap(dev_t dev, unsigned count) { kobj_unmap(cdev_map, dev, count); diff --git a/include/linux/cdev.h b/include/linux/cdev.h index f8763615a5f2..043168df1d8f 100644 --- a/include/linux/cdev.h +++ b/include/linux/cdev.h @@ -25,6 +25,7 @@ struct cdev *cdev_alloc(void); void cdev_put(struct cdev *p); int cdev_add(struct cdev *, dev_t, unsigned); +int device_add_cdev(struct device *dev, struct cdev *); void cdev_del(struct cdev *);