On Mon, Dec 14, 2009 at 11:34:31AM +0100, Kay Sievers wrote:
> On Mon, Dec 14, 2009 at 11:28, Johannes Stezenbach <js@xxxxxxxxx> wrote:
> > On Mon, Dec 14, 2009 at 10:14:50AM +0100, Martin Pitt wrote:
> >>
> >> A gotcha that I see here is that the force_release only ever gets
> >> appended to. I. e. whenever we run udevtrigger, we'd append the same
> >> keys again. POSIX shell doesn't have elaborate substring matching
> >> capabilities like bash's ${x/pattern/string}, so it might not be too
> >> easy to check if we already have a key in POSIX sh. (But please don't
> >> call grep in a loop; let's rather rewrite this bit in C). There might
> >> be some trickery with splitting by IFS=, into an array or so, if you
> >> want to keep using sh?
> >
> > The problem is that force_release is preset by the kernel, so
> > in order to do what you want we need either
> > a) pass both old and new key list on "change"
> > b) save initial force_release value to a file on "add"
> > and use the file on "change"
>
> It should just not mangle the sysfs string if the value is already
> contained. Why would you need to store anything between a "change" and
> "add" event? Both events are handled the same way, and the two
> independent events run one after each other.
I don't understand. I only append to the force_release attribute
because the kernel already removes duplicates.
However, what does not work this way is to remove scancodes from
force_release. I thought that was what Martin wanted to accomplish
on the "change" event.
> I guess the logic to append a value to the sysfs string only if needed
> should be done in a tine C program, or a sed script with a RUN+= call
> directly to sed maybe can be used ...
sed cannot do hex to decimal conversion, but awk could be used.
Thanks,
Johannes
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