John Youn <John.Youn@xxxxxxxxxxxx> writes:
> Hi,
>
> I would like to port the following commit from 4.6 to older kernels.
>
> 1a85329171094951956a37acc8abb7e51c1e742e ("usb: gadget: composite:
> Return bcdUSB 0x0310")
>
> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=1a85329171094951956a37acc8abb7e51c1e742e
You are of course free to do that. Why do you need it to be in
everybody else's stable kernels?
Ref the current discussion on "security fixes only" stable kernels. It
seems some people think that the current stable rules already allow too
much potentionally harmful stuff. Allowing new features like this isn't
going to help there...
> There is a some concern that revving the bcdUSB to 0x0310 will cause
> problems for SuperSpeed devices based on older kernels that don't
> otherwise have any USB 3.1 specific code.
>
> On the device side I don't think there will be any problems because
> there aren't really any checks against bcdUSB. We just set it to
> 0x0300 (0x0310 for kernel 4.6+) based on if the gadget tells us it
> supports SuperSpeed or higher.
>
> And I don't think there should be any problems for a host connecting
> to these devices since any SuperSpeed capable host should know about
> bcdUSB = 0x03XX. And I don't think the USB spec defines any different
> functionality based solely on 0x0300 vs 0x0310.
Luckily I'm not the one to decide this, but I believe
Documentation/stable_kernel_rules.txt require a lot more than that.
Could you relate this to "fixing a bug" somehow?
> The reason for this backport is that the USB CV tool now checks this
> and ostensibly USB IF certification will require this for "new"
> devices. So if you are basing a new device on a kernel older than 4.6,
> it will not pass CV.
That sounds like a feature to me ;)
Bjørn
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