Hi.
On Wed, 2005-03-09 at 08:54, Pavel Machek wrote:
> Hi!
>
> > > For user suspends (made through sysfs) the user may want to convey
> > > arbitrary information to a driver, things like which clocks to turn
> > > off, which power level to change to, and so on. This information
> > > will vary from driver to driver, and the PM core shouldn't even try to
> > > impose any sort of structure on it. I think the best approach will be
> > > to pass to the driver a character pointer giving the data written to
> > > /sys/.../power/state, so that users can send whatever they want just
> > > by writing it to the file. This means adding an additional field to
> > > pm_message_t.
> >
> > Uh, that would really suck. This would entail a string parser in every
> > driver, which is what we wanted to get away from with sysfs. A better way
> > would be to have a driver export a file with the specific features that it
> > supports encoded in a meaningful and efficient way (i.e. a fixed-length
> > string, character, or constant).
>
> [I'm not advocating char *, but: ] string parser in every driver does
> not neccessarily seem evil to me. In most cases it will be
>
> if (!strcmp(state.string, "suspend")) {
> do something
> }
>
> ..and that seems quite okay.
A number would be faster to parse. Perhaps we could use an ul for the
action, and a string for the parameters? That way you don't have to do n
strcmps in your drivers, but still get flexibility with the parameters.
The numbers for actions could also be standardised and perhaps used in
inter-driver communication (eg to get children suspended as well)?
Nigel
--
Nigel Cunningham
Software Engineer, Canberra, Australia
http://www.cyclades.com
Bus: +61 (2) 6291 9554; Hme: +61 (2) 6292 8028; Mob: +61 (417) 100 574
Maintainer of Suspend2 Kernel Patches http://suspend2.net
