On Thu, Dec 28, 2017 at 10:42:21PM +0100, Bartosz Golaszewski wrote: > 2017-12-28 12:28 GMT+01:00 Johan Hovold <johan@xxxxxxxxxx>: > > On Wed, Dec 27, 2017 at 03:10:38PM +0100, Bartosz Golaszewski wrote: > >> This function can fail with -EBUSY, but we don't check its return > >> value in at24_remove(). Bail-out of remove() if nvmem_unregister() > >> doesn't succeed. > >> > >> Signed-off-by: Bartosz Golaszewski <brgl@xxxxxxxx> > >> --- > >> drivers/misc/eeprom/at24.c | 6 ++++-- > >> 1 file changed, 4 insertions(+), 2 deletions(-) > >> > >> diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c > >> index e79833d62284..fb21e1c45115 100644 > >> --- a/drivers/misc/eeprom/at24.c > >> +++ b/drivers/misc/eeprom/at24.c > >> @@ -684,11 +684,13 @@ static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id) > >> static int at24_remove(struct i2c_client *client) > >> { > >> struct at24_data *at24; > >> - int i; > >> + int i, ret; > >> > >> at24 = i2c_get_clientdata(client); > >> > >> - nvmem_unregister(at24->nvmem); > >> + ret = nvmem_unregister(at24->nvmem); > >> + if (ret) > >> + return ret; > > > > I don't this makes much sense as a driver cannot refuse an unbind by > > returning an errno from remove(). The return value is simply ignored, > > remove() will never be called again, and you'd leave everything in an > > inconsistent state. > > > > Cc: Srinivas > > Hi Johan, > > I blindly assumed that if there's a return value in remove() then > someone cares about it. In that case all users of nvmem_unregister() > that check the return value and bail-out of remove() on failure are > wrong and in the (very unlikely) event that this routine fails, we > leak all resources. I see only one other driver that bails out on deregistration errors (lpc18xx_eeprom.c), even if other drivers do indeed propagate errors. > > It looks like the nvmem code grabs a reference to the owning module > > in __nvmem_device_get() which would at least prevent a module unload > > while another driver is using the device. And the (sysfs) userspace > > interface should be fine as device removal is handled by the kernfs > > code. > > Indeed. I believe we should remove the -EBUSY return case from > nvmem_register() and just do what gpiolib does - scream loud > (dev_crit()) when someone forces a module unload or otherwise > unregisters the device if some cells are still requested. This would > also allow us to eventually add a devres variant for nvmem_register(). I really don't like using devres for deregistration since typically you'd need a follow-on deallocation step or you end up with a weird asymmetric interface, but that's another story. And again, the module unload case would not be a problem, at least when the device is looked up from device tree, as nvmem then grabs a module reference. Johan