On Sunday 07 June 2009 00:20:26 Jon Smirl wrote:
> On Sat, Jun 6, 2009 at 9:00 AM, Hans Verkuil<hverkuil@xxxxxxxxx> wrote:
> > Hi all,
> >
> > For video4linux we sometimes need to probe for a single i2c address.
> > Normally you would do it like this:
>
> Why does video4linux need to probe to find i2c devices? Can't the
> address be determined by knowing the PCI ID of the board?
There are two reasons we need to probe: it is either because when the board
was added no one bothered to record which chip was on what address (this
happened in particular with old drivers like bttv) or because there is
simply no other way to determine the presence or absence of an i2c device.
E.g. there are three versions of one card: without upd64083 (Y/C separation
device) and upd64031a (ghost reduction device), with only the upd64031a and
one with both. Since they all have the same PCI ID the only way to
determine the model is to probe.
Regards,
Hans
>
> > static const unsigned short addrs[] = {
> > addr, I2C_CLIENT_END
> > };
> >
> > client = i2c_new_probed_device(adapter, &info, addrs);
> >
> > This is a bit awkward and I came up with this macro:
> >
> > #define V4L2_I2C_ADDRS(addr, addrs...) \
> > ((const unsigned short []){ addr, ## addrs, I2C_CLIENT_END })
> >
> > This can construct a list of one or more i2c addresses on the fly. But
> > this is something that really belongs in i2c.h, renamed to I2C_ADDRS.
> >
> > With this macro we can just do:
> >
> > client = i2c_new_probed_device(adapter, &info, I2C_ADDRS(addr));
> >
> > Comments?
> >
> > Regards,
> >
> > Hans
> >
> > --
> > Hans Verkuil - video4linux developer - sponsored by TANDBERG Telecom
> > --
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--
Hans Verkuil - video4linux developer - sponsored by TANDBERG Telecom
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