> From the kernel point of view, (most of) the various sub-devices in a
> media
> device are arranged in a tree of kernel objects. Most of the time we have
> an
> I2C controller and various devices sitting on the I2C bus, one or several
> video devices that sit on some internal bus (usually a SoC internal bus
> for
> the most complex and recent platforms), and possibly SPI and other devices
> as
> well.
>
> Realizing that, as all those sub-devices are already exposed in sysfs in
> one
> way or the other, it was tempting to add a few attributes and soft links
> to
> solve the media controller problem.
I just wanted to make one clarification: sub-devices are usually, but not
always mapped 1-to-1 to a true kernel device. But sub-devices are an
abstract concept and it is possible to have multiple sub-devices exposed
by a single kernel device. Or even to have one sub-device covering two or
more kernel devices (no such beast exists, but nothing prevents this
technically).
I know of two instances where the sub-device has no sysfs counterpart. And
I expect more will follow.
Regards,
Hans
--
Hans Verkuil - video4linux developer - sponsored by TANDBERG Telecom
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