[RFC] musb: removing otg protocol support

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Fri, Mar 16, 2018 at 02:09:51PM -0500, Bin Liu wrote:
> Hi,
> 
> The kernel usb stack and musb drivers have gone through some changes in
> the past several kernel versions, such as adding otg fsm, musb runtime
> PM, and musb otg state moving from musb to musb->xceiv... I am wondering
> if the otg protocol (hnp, srp) functions are already broken in the musb
> drivers, but I don't have a platform to confirm it.
> 
> Do we know by any chance there is still someone using the musb otg
> functions in any relatively newer kernel and we still need to support
> otg in musb?  If not, I am thinking to clean up the otg functions in
> musb drivers to make the code easy to read and maintain.

By "clean up" do you mean "delete it"?  :)

I don't know of any real OTG hardware that ever shipped, does anyone
else?

> If we can make the conclusion to remove it, I propose the patch below
> to disable musb otg first, then clean up the driver later if nobody
> complains about the otg function removal.

It will take years for people who make these types of devices to notice
that OTG is removed, so be careful about this.  Refactor away, but
watch out you don't break someone's stuff and get told about it in 2
years :(

good luck!

greg k-h
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