Messages in this thread | | | Subject | Re: [PATCH] rfkill: allocate static minor | From | Marcel Holtmann <> | Date | Thu, 24 Oct 2019 22:23:57 +0200 |
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Hi Greg,
>> udev has a feature of creating /dev/<node> device-nodes if it finds >> a devnode:<node> modalias. This allows for auto-loading of modules that >> provide the node. This requires to use a statically allocated minor >> number for misc character devices. >> >> However, rfkill uses dynamic minor numbers and prevents auto-loading >> of the module. So allocate the next static misc minor number and use >> it for rfkill. > > As rfkill has been around for a long time, what new use case is needing > to auto-load this based on a major number?
we have bug reports from iwd users where it fails opening /dev/rfkill. Since iwd can be actually started before the WiFi hardware is fully probed and all its drivers are loaded, we have a race-condition here if rfkill is not capable of auto-loading.
The difference is really that iwd is a fully self-contained WiFi daemon compared to wpa_supplicant which is just some sort of helper. iwd is fully hot plug capable as well compared to wpa_supplicant. It looks like this is exposing the race condition for our users. Frankly, we should have fixed rfkill a long time ago when we fixed uinput, uhid etc, but seems we forgot it. I assume mainly because it magically got loaded in time by some module dependencies.
Regards
Marcel
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