Re: [PATCH -next] xhci: fix two places when dealing with return value of function xhci_check_args

[Hongyu Xie]

Hi Greg,

On 2022/1/26 18:50, Greg KH wrote:
> A: http://en.wikipedia.org/wiki/Top_post
> Q: Were do I find info about this thing called top-posting?
> A: Because it messes up the order in which people normally read text.
> Q: Why is top-posting such a bad thing?
> A: Top-posting.
> Q: What is the most annoying thing in e-mail?
>
> A: No.
> Q: Should I include quotations after my reply?
>
> http://daringfireball.net/2007/07/on_top
>
> On Wed, Jan 26, 2022 at 06:22:45PM +0800, 谢泓宇 wrote:
> > 1."What problem?
> > r8152_submit_rx needs to detach netdev if -ENODEV happened, but -ENODEV will
> > never happen
> > because xhci_urb_enqueue only returns -EINVAL if the return value of
> > xhci_check_args <= 0. So
> > r8152_submit_rx will will call napi_schedule to re-submit that urb, and this
> > will cause infinite urb
> > submission.
> Odd line-wrapping...
Sorry about my last reply.
> Anyway, why is this unique to this one driver?  Why does it not show up
> for any other driver?
The whole thing is not about a particular driver. The thing is 
xhci_urb_enqueue shouldn't change the return value of xhci_check_args 
from -ENODEV to -EINVAL. Many other drivers only check if the return 
value of xchi_check_args is <= 0.
> > The whole point is, if xhci_check_args returns value A, xhci_urb_enqueque
> > shouldn't return any
> > other value, because that will change some driver's behavior(like r8152.c).
> But you are changing how the code currently works.  Are you sure you
> want to have this "succeed" if this is on a root hub?
Yes, I'm changing how the code currently works but not on a root hub.
> > 2."So if 0 is returned, you will now return that here, is that ok?
> > That is a change in functionality.
> > But this can only ever be the case for a root hub, is that ok?"
> >
> > It's the same logic, but now xhci_urb_enqueue can return -ENODEV if xHC is
> > halted.
> > If it happens on a root hub,  xhci_urb_enqueue won't be called.
> >
> > 3."Again, this means all is good?  Why is this being called for a root hub?"
> >
> > It is the same logic with the old one, but now xhci_check_streams_endpoint
> > can return -ENODEV if xHC is halted.
> This still feels wrong to me, but I'll let the maintainer decide, as I
> don't understand why a root hub is special here.

Thanks please. usb_submit_urb will call usb_hcd_submit_urb. And 
usb_hcd_submit_urb will call rh_urb_enqueue if it's on a root hub 
instead of calling hcd->driver->urb_enqueue(which is xhci_urb_enqueue in 
this case).

> thanks,
>
> greg k-h

thanks,

Hongyu Xie