linux-kernel - Re: [PATCH v3 0/4] support USB offload feature

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Date:   Mon, 21 Mar 2022 19:06:31 +0900
From:   Jung Daehwan <dh10.jung@...sung.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Mathias Nyman <mathias.nyman@...el.com>,
        "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>, sc.suh@...sung.com
Subject: Re: [PATCH v3 0/4] support USB offload feature

On Mon, Mar 21, 2022 at 10:32:25AM +0100, Greg Kroah-Hartman wrote:
> On Mon, Mar 21, 2022 at 06:24:09PM +0900, Jung Daehwan wrote:
> > On Mon, Mar 21, 2022 at 10:14:23AM +0100, Greg Kroah-Hartman wrote:
> > > On Mon, Mar 21, 2022 at 05:59:50PM +0900, Daehwan Jung wrote:
> > > > This patchset is for USB offload feature, which makes Co-processor to use
> > > > some memories of xhci. Especially it's useful for USB Audio scenario.
> > > > Audio stream would get shortcut because Co-processor directly write/read
> > > > data in xhci memories. It could get speed-up using faster memory like SRAM.
> > > > That's why this gives vendors flexibilty of memory management.
> > > > Several pathches have been merged in AOSP kernel(android12-5.10) and I put
> > > > together and split into 3 patches. Plus let me add user(xhci-exynos)
> > > > module to see how user could use it.
> > > > 
> > > > To sum up, it's for providing xhci memories to Co-Processor.
> > > > It would cover DCBAA, Device Context, Transfer Ring, Event Ring, ERST.
> > > > It needs xhci hooks and to export some xhci symbols.
> > > > 
> > > > Changes in v2 :
> > > > - Fix commit message by adding Signed-off-by in each patch.
> > > > - Fix conflict on latest.
> > > > 
> > > > Changes in v3 :
> > > > - Remove export symbols and xhci hooks which xhci-exynos don't need.
> > > > - Modify commit message to clarify why it needs to export symbols.
> > > > - Check compiling of xhci-exynos.
> > > 
> > > As I asked for in the previous submission, you MUST have a user for
> > > these hooks, otherwise we can not accept them (nor would you WANT us to
> > > accept them).  Please fix that up and add them to the next submission as
> > > we can not do anything with this one.
> > > 
> > > thanks,
> > > 
> > > greg k-h
> > > 
> > 
> > Hi greg,
> > 
> > I've submitted the user(xhci-exynos) together on the last patch of the patchset.
> > You can see xhci-exynos uses these hooks and symbols.
> > 
> > [PATCH v3 4/4] usb: host: add xhci-exynos driver
> 
> Then this is not "offload" hooks at all.  They are merely "support
> another xhci platform driver, right?

Yes, right.

> 
> I see a lot of exports and function hooks added, are they _ALL_ used by
> the xhci driver?  If so, please reword this series as it is not very
> obvious at all what you are doing.

Yes, they are all used by the xhci driver. Is it OK for me to use "xhci-exynos"
instead of "USB offload" on series like below?

[v3, 0/4] add xhci-exynos driver

This patchset is for support xhci-exynos driver....
....

  usb: host: export symbols for xhci-exynos to use xhci hooks
  usb: host: add xhci hooks for xhci-exynos
  usb: host: add some to xhci overrides for xhci-exynos
  usb: host: add xhci-exynos driver

Best Regards,
Jung Daehwan

> 
> thanks,
> 
> greg k-h
>