On Thu, Nov 18, 2021 at 06:22:58AM -0800, Guenter Roeck wrote: > On 11/18/21 3:32 AM, Dan Carpenter wrote: > > The extcon_get_extcon_dev() function returns error pointers on error > > and NULL when it's a -EPROBE_DEFER defer situation. There are eight > > callers and only two of them handled this correctly. In the other > > callers an error pointer return would lead to a crash. > > > > What prevents crashes is that errors can only happen in the case of > > a bug in the caller or if CONFIG_EXTCON is disabled. Six out of > > eight callers use the Kconfig to either depend on or select > > CONFIG_EXTCON. Thus the real life impact of these bugs is tiny. > > > > Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx> > > --- > > The two callers where the drivers can be built without CONFIG_EXTCON > > are TYPEC_FUSB302 and CHARGER_MAX8997. > > > [ ... ] > > diff --git a/drivers/usb/typec/tcpm/fusb302.c b/drivers/usb/typec/tcpm/fusb302.c > > index 7a2a17866a82..8594b59bd527 100644 > > --- a/drivers/usb/typec/tcpm/fusb302.c > > +++ b/drivers/usb/typec/tcpm/fusb302.c > > @@ -1706,8 +1706,8 @@ static int fusb302_probe(struct i2c_client *client, > > */ > > if (device_property_read_string(dev, "linux,extcon-name", &name) == 0) { > > chip->extcon = extcon_get_extcon_dev(name); > > - if (!chip->extcon) > > - return -EPROBE_DEFER; > > + if (IS_ERR(chip->extcon)) > > + return PTR_ERR(chip->extcon); > > Why does the code not need to return -EPROBE_DEFER ? The description states > that NULL is returned in that situation. Doesn't that mean that defer situations > are no longer handled with this patch in place ? I'm not sure I understand what you are saying here. In the original code, extcon_get_extcon_dev() would return NULL and relied on the callers to change NULL into a -EPROBE_DEFER. If extcon_get_extcon_dev() returned ERR_PTR(-EINVAL) (which is impossible as mentioned) the it would lead to a crash. In the new code, the extcon_get_extcon_dev() function returns -EPROBE_DEFER directly so the caller code is much simpler. > > Also, with this patch in place, the code will no longer work if extcon is disabled, > because extcon_get_extcon_dev() will return -ENODEV and the above code will bail out. > The behavior of the code wasn't optimal in that case (it would wait until timeout > in tcpm_get_current_limit() before returning), but at least it didn't fail. Huh. You are right. Initialy I thought that tcpm_get_current_limit() would crash. This is one of the two drivers which I mentioned that can be built without CONFIG_EXTCON. I will modify the version of extcon_get_extcon_dev() where CONFIG_EXTCON is disabled to return NULL. That is the standard/correct way to write these. That will turn tcpm_get_current_limit() into a no-op. A belt and suspenders approach might be to modify the Kconfig so this driver selects CONFIG_EXTCON. regards, dan carpenter