Merging device drivers to LK tree

[greg@kroah.com (Greg KH)]

On Tue, Mar 14, 2017 at 05:14:12PM -0400, valdis.kletnieks at vt.edu wrote:
> On Tue, 14 Mar 2017 21:59:20 +0100, Bj?rn Mork said:
> 
> > And another one:
> >
> >  5.) vendor independent class drivers
> >
> >
> > IMHO perfect for the independent developer since there will be
> > documentation available.  The USB class specs are freely available for
> > example.
> 
> Hmm... /sys/class has a bunch of stuff already.

/sys/class has nothing to do with a USB class specification :)

> How many class drivers
> are missing from there? And more importantly, class drivers for a hardware
> class that's actually available (i.e. neither extinct or not shipping yet)?

A USB "class" is a set of devices that follow a published specification.
Like a USB HID device (keyboard/mouse/etc.)  These are all published on
the usb.org website.  I think there still are a few class specs that are
not yet implemented on Linux, usually because no one actually made any
devices for them, or not enough that anyone really cares.

A /sys/class/ entry is a kernel subsystem that describes a set of
devices that interact with userspace in a defined way.  Like an "input"
class.  That is how userspace interacts with _all_ keyboards, be they
USB or PS/2 or i2c or whatever.

Hope this helps,

greg k-h