Re: Aspeed vhub configuration

[Greg KH <greg@kroah.com>]

On Tue, Jul 02, 2019 at 09:33:11PM +1000, Benjamin Herrenschmidt wrote:
> Hi folks !
> 
> The Aspeed USB gadget "vhub" implements a hub emulation with a number
> of UDCs representing the hub slots. It's working ok now and has been
> upstream for a bit, however, one thing that's been annoying to some
> users is that I've just hard coded the hub's device descriptor. IE, the
> vendor/product ID, strings etc...
> 
> Various BMC SW stack vendors want to customize that, also possibly the
> number of ports etc...
> 
> I originally thought about configfs but after more thoughts I don't
> think it's really a good fit. The vhub is a fixed thing. When you have
> the HW, you have that hub, it's not like you can create different
> things, and populate differently.
> 
> That leaves me with two approaches, that aren't mutually exclusive, but
> I'd like to run them past the folks here before I start coding:
> 
>  - The defaults, currently hard coded, could be replaced with Kconfig
> options.
> 
>  - The device-tree node could contain optional override of those
> defaults, allowing a vendor to customize the hub for a given board.
> It's not per-se a HW description, but the device-tree is also fairly
> commonly used for HW configuration, even if some people disagree with
> me on that one (hint: they are wrong :-)
> 
>  - I could add sysfs properties underneath the vhub device instance to
> customize it. This would also allow userspace to control whether the
> hub is "connected" to the host or not, which could be useful, some
> systems don't want it to always be there. Today there's no choice.
> 
> Any other option ? If somebody says netlink I will scream :)

DT seems like the logical choice, I'll not object to that.

thanks,

greg k-h