linux-kernel - Re: [PATCH v1 1/4] usb: host: export symbols for xhci hooks usage

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Date:   Tue, 29 Mar 2022 11:43:51 +0900
From:   Jung Daehwan <dh10.jung@...sung.com>
To:     Krzysztof Kozlowski <krzk@...nel.org>
Cc:     Mathias Nyman <mathias.nyman@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "open list:USB XHCI DRIVER" <linux-usb@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        Howard Yen <howardyen@...gle.com>,
        Jack Pham <jackp@...eaurora.org>,
        Puma Hsu <pumahsu@...gle.com>,
        "J . Avila" <elavila@...gle.com>,
        "chihhao . chen" <chihhao.chen@...iatek.com>, sc.suh@...sung.com,
        cpgs@...sung.com, cpgsproxy5@...sung.com
Subject: Re: [PATCH v1 1/4] usb: host: export symbols for xhci hooks usage

On Fri, Mar 25, 2022 at 12:36:20PM +0100, Krzysztof Kozlowski wrote:
> On 25/03/2022 02:28, Jung Daehwan wrote:
> > On Wed, Mar 23, 2022 at 10:41:23AM +0100, Krzysztof Kozlowski wrote:
> >> On 23/03/2022 03:58, Jung Daehwan wrote:
> >>> On Mon, Mar 07, 2022 at 10:59:06AM +0100, Krzysztof Kozlowski wrote:
> >>>> On 04/03/2022 07:23, Daehwan Jung wrote:
> >>>>> Export symbols for xhci hooks usage:
> >>>>> 	xhci_ring_free
> >>>>> 	- Allow xhci hook to free xhci_ring.
> >>>>
> >>>> Instead of copying-pasting the name of function, please explain why do
> >>>> you need these symbols exported.
> >>>>
> >>>> The "Why" is actually one of most important questions, because "what is
> >>>> this patch doing" we can easily see...
> >>>>
> >>>>>
> >>>>> 	xhci_get_slot_ctx
> >>>>> 	- Allow xhci hook to get slot_ctx from the xhci_container_ctx
> >>>>> 	  for getting the slot_ctx information to know which slot is
> >>>>> 	  offloading and compare the context in remote subsystem memory
> >>>>> 	  if needed.
> >>>>>
> >>>>
> >>>>
> >>>> Best regards,
> >>>> Krzysztof
> >>>>
> >>>
> >>> Hi Krzysztof
> >>>
> >>> xhci_ring_free has been removed from v3..
> >>> The reason why I want to export is for managing vendor specific ring.
> >>> I want to alloc and free vendor specific ring on specific address.
> >>> It's done with xhci hooks.
> >>
> >> It's better, but still does not explain why these have to be exported.
> >> Please mention where are these hooks going to be. Where are they
> >> implemented. I actually expect all of these exports to be used in your
> >> patchset.
> >>
> >> Best regards,
> >> Krzysztof
> >>
> > 
> > OK. How about adding call stack like below?
> > 
> > xhci_free_endpoint_ring -> xhci_vendor_free_transfer_ring(xhck hooks
> > ops) -> xhci_ring_free
> 
> What I would like to see is high level explanation, why do you need
> these functions exported. Such call trace does not answer this, because
> you do not need to export functions just to call the. You need to export
> them for modules, so this means that some modules (which - need names)
> will be using these functions. Three or four sentences are usually
> enough to explain it.
> 
> 
> Best regards,
> Krzysztof
> 

I got it. I'm going to modify it on next submission.

Best Regards,
Jung Daehwan