linux-kernel - Re: [PATCH v20 1/4] usb: Add support for Intel LJCA device

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Message-ID: <2023101653-shiftless-scorebook-19e3@gregkh>
Date:   Mon, 16 Oct 2023 17:19:13 +0200
From:   "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
To:     "Wu, Wentong" <wentong.wu@...el.com>
Cc:     "Shevchenko, Andriy" <andriy.shevchenko@...el.com>,
        Hans de Goede <hdegoede@...hat.com>,
        "oneukum@...e.com" <oneukum@...e.com>,
        "wsa@...nel.org" <wsa@...nel.org>,
        "andi.shyti@...ux.intel.com" <andi.shyti@...ux.intel.com>,
        "broonie@...nel.org" <broonie@...nel.org>,
        "bartosz.golaszewski@...aro.org" <bartosz.golaszewski@...aro.org>,
        "linus.walleij@...aro.org" <linus.walleij@...aro.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
        "linux-spi@...r.kernel.org" <linux-spi@...r.kernel.org>,
        "sakari.ailus@...ux.intel.com" <sakari.ailus@...ux.intel.com>,
        "Wang, Zhifeng" <zhifeng.wang@...el.com>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v20 1/4] usb: Add support for Intel LJCA device

On Mon, Oct 16, 2023 at 03:05:09PM +0000, Wu, Wentong wrote:
> > From: Shevchenko, Andriy
> > On Mon, Oct 16, 2023 at 08:52:28AM +0300, Wu, Wentong wrote:
> > > > On 10/13/23 22:05, Shevchenko, Andriy wrote:
> > > > > On Thu, Oct 12, 2023 at 01:14:23PM +0200, Hans de Goede wrote:
> > 
> > <snip>
> > 
> > > > >> Ah ok, I see. So the code:
> > > > >>
> > > > >> 1. First tries to find the matching child acpi_device for the
> > > > >> auxdev by ADR
> > > > >>
> > > > >> 2. If 1. fails then falls back to HID + UID matching
> > > > >>
> > > > >> And there are DSDTs which use either:
> > > > >>
> > > > >> 1. Only use _ADR to identify which child device is which, like the example
> > > > >>    DSDT snippet from the commit msg.
> > > > >>
> > > > >> 2. Only use _HID + _UID like the 2 example DSDT snippets from me
> > > > >> email
> > > > >>
> > > > >> But there never is a case where both _ADR and _HID are used at
> > > > >> the same time (which would be an ACPI spec violation as Andy said).
> > > > >>
> > > > >> So AFAICT there is no issue here since  _ADR and _HID are never
> > > > >> user at the same time and the commit message correctly describes
> > > > >> scenario 1. from above, so the commit message is fine too.
> > > > >>
> > > > >> So I believe that we can continue with this patch series in its
> > > > >> current v20 form, which has already been staged for going into
> > > > >> -next by Greg.
> > > > >>
> > > > >> Andy can you confirm that moving ahead with the current version
> > > > >> is ok ?
> > > > >
> > > > > Yes as we have a few weeks to fix corner cases.
> > > > >
> > > > > What I'm worrying is that opening door for _ADR that seems never
> > > > > used is kinda an overkill here (resolving non-existing problem).
> > > >
> > > > I assume that there actually some DSDTs using the _ADR approach and
> > > > that this support is not there just for fun.
> > >
> > > right, it's not for fun, we use _ADR here is to reduce the maintain
> > > effort because currently it defines _HID for every new platform and
> > > the drivers have to be updated accordingly, while _ADR doesn't have that
> > problem.
> > 
> > But this does not confirm if you have such devices. Moreover, My question
> > about _CID per function stays the same. Why firmware is not using it?
> 
> Yes, both _ADR and _CID can stop growing list in the driver. And for _ADR, it also
> only require one ID per function. I don't know why BIOS team doesn't select _CID,
> but I have suggested use _ADR internally, and , to make things moving forward,
> the driver adds support for _ADR here first. 
> 
> But you're right, _CID is another solution as well, we will discuss it with firmware
> team more.

Should I revert this series now until this gets sorted out?

thanks,

greg k-h