On Tue, Feb 04, 2025 at 01:55:54PM +0100, Greg Kroah-Hartman wrote: > On Tue, Feb 04, 2025 at 01:04:13PM +0100, Danilo Krummrich wrote: > > On Tue, Feb 04, 2025 at 12:52:34PM +0100, Greg Kroah-Hartman wrote: > > > On Tue, Feb 04, 2025 at 12:44:03PM +0100, Danilo Krummrich wrote: > > > > On Tue, Feb 04, 2025 at 12:09:13PM +0100, Greg Kroah-Hartman wrote: > > > > > Many drivers abuse the platform driver/bus system as it provides a > > > > > simple way to create and bind a device to a driver-specific set of > > > > > probe/release functions. Instead of doing that, and wasting all of the > > > > > memory associated with a platform device, here is a "faux" bus that > > > > > can be used instead. > > > > > > > > > > Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> > > > > > --- > > > > > v2: - renamed bus and root device to just "faux" thanks to Thomas > > > > > - removed the one-driver-per-device and now just have one driver > > > > > entirely thanks to Danilo > > > > > - kerneldoc fixups and additions and string handling bounds checks > > > > > hanks to Andy > > > > > - coding style fix thanks to Jonathan > > > > > - tested that the destroy path actually works > > > > > > > > > > drivers/base/Makefile | 2 +- > > > > > drivers/base/base.h | 1 + > > > > > drivers/base/faux.c | 196 ++++++++++++++++++++++++++++++++++++ > > > > > drivers/base/init.c | 1 + > > > > > include/linux/device/faux.h | 31 ++++++ > > > > > 5 files changed, 230 insertions(+), 1 deletion(-) > > > > > create mode 100644 drivers/base/faux.c > > > > > create mode 100644 include/linux/device/faux.h > > > > > > > > I really like it, it's as simply as it can be. > > > > > > > > Please find one nit below, otherwise > > > > > > > > Reviewed-by: Danilo Krummrich <dakr@xxxxxxxxxx> > > > > > > > > > > > > > > +/** > > > > > + * faux_device_destroy - destroy a faux device > > > > > + * @faux_dev: faux device to destroy > > > > > + * > > > > > + * Unregister and free all memory associated with a faux device that was > > > > > + * previously created with a call to faux_device_create(). > > > > > > > > Can we really claim that this frees all memory? Someone can still have a > > > > reference to the underlying struct device, right? > > > > > > That "someone" is the person that had the original device pointer passed > > > to it, so if that person then calls faux_device_destroy(), yes, that > > > should all be properly cleaned up. > > > > > > But even if it isn't, the device is destroyed and gone from sysfs, and > > > whenever that final final put_device() is called, the memory will then > > > be freed by the driver core itself. > > > > Oh indeed, the code here is perfectly fine. I just wanted to say that calling > > faux_device_destroy() is not a guarantee that "all memory associated with a > > faux device" is actually freed, as the kernel-doc comment above says (or at > > least implies). > > > > So, the concern only was that the comment could be confusing, as in "How can > > faux_device_destroy() free the memory, if I still have a separate reference to > > this thing?" (which it clearly would not). > > Documentation is hard :) > > Can you think of some wording here that would explain this better? > Something like "after you call this, you can't touch the pointer you > passed into here" is what I'm going for. I would probably just say that it drops the initial reference created by faux_device_create(), e.g.: "Unregister a faux device and drop the initial reference obtained through faux_device_create()." --
