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. > 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(). What do you think Srinivas? Best regards, Bartosz Golaszewski