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SubjectRe: modalias char-major-10-130
Hi Jean,

> All watchdog drivers include:
>
> MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
>
> which causes a modalias char-major-10-130 to be added to every watchdog
> driver module. As a result, any access to /dev/watchdog on a system with
> no watchdog driver loaded and working will result in an attempt to load
> several dozen drivers. At best one or two will actually work, the others
> will:
>
> * Waste time failing to load.
> * Waste memory succeeding to load but not finding any device to bind to.
> * Pollute the kernel log.
> * Sometimes even load while they should not and break the system. I just
> had a report about advantechwdt doing that on some systems.
>
> And the attempt order will presumably be random, so it might as well
> load softdog before a hardware-based watchdog which would have been
> preferred.
>
> This looks so 90s. Drivers for enumerated devices have hardware-based
> modaliases, so char-major-10-130 shouldn't be needed. Other drivers
> should certainly not be loaded randomly if they need to poke the
> hardware to detect the presence of a supported device.
>
> My opinion is that the char-major-10-130 modalias should ONLY be defined
> by user-space, when the user knows he/she needs a watchdog driver which
> doesn't support auto-loading via hardware-based auto-loading.
>
> So, can we please get rid of all these
> MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR) statements? They do more harm than
> good as far as I can see.

You have a valid point: There were we have modaliases and other detection
mechanism we should indeed remove them. The rest should be evaluated
afterwards on a case by case basis. Certain intel based drivers should
(like advantechwdt) should indeed be fixed because they poke in the hardware
directly and can't be really detected.

Kind regards,
Wim.



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