[question] between probe() and open()
Ezequiel García
elezegarcia at gmail.com
Sat Feb 25 17:09:49 EST 2012
Hello,
This is a question in general about usb drivers and
in particular about easycap driver.
Is there any way a driver can be accesed
between after usb_probe() but before device open()?
I guess not, since any further operation on
the device needs a struct file pointer, i.e. a file descriptor on
the user side.
In particular:
easycap driver currently calls reset() on usb_probe(),
reset() does some hardware initialization among other stuff.
However, the reset() is called once again on open().
This seems redundant, right?
The reset() is a heavy function since it access the hardware, so
it would be benefitial to change it,
but I would like someone to ack this, since it is not so trivial.
Some measures on the device shows how heavy the reset() is:
# calling reset() on usb_probe()
time modprobe easycap
real 0m1.516s
user 0m0.000s
sys 0m0.009s
---
# not calling reset() on usb_probe()
time modprobe easycap
real 0m0.003s
user 0m0.000s
sys 0m0.002s
Thanks,
Ezequiel.
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