Speed up DeviceKit device probing on really slow devices

Linus Torvalds torvalds at linux-foundation.org
Wed Jan 20 11:58:33 PST 2010

On Wed, 20 Jan 2010, David Zeuthen wrote:
> Well, the school of thought here is to collect as a lot of data (but not
> all - there's a fine line) about the device and store it in the udev
> database.

That's fine - but please keep in mind to collect it _after_ you have 
exposed the device and made it useful. Because if it holds up actual real 
work, it's a bad thing, not a feature.

Also keep in mind that some devices are rather unhappy with access 
patterns that don't look like Windows. They've been tested with Windows, 
and that's it. The kernel tries to fix them up, but there's a real risk 
that being clever can make cheap USB sticks unusable.

Or not so cheap things, for that matter. Some iPod's are an example of 
"crap that locks up if you try to read at the end of the device", where 
the RAID probing literally killed the device (until the kernel got taught 
to limit the size below what the device actually claimed).

So there are real downsides.


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