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Date:   Mon, 28 Feb 2022 10:28:53 -0800
From:   "mka@chromium.org" <mka@chromium.org>
To:     "Linyu Yuan (QUIC)" <quic_linyyuan@quicinc.com>
Cc:     "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
        "Tao Wang (Consultant) (QUIC)" <quic_wat@quicinc.com>,
        "balbi@kernel.org" <balbi@kernel.org>,
        "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
        "dianders@chromium.org" <dianders@chromium.org>,
        "frowand.list@gmail.com" <frowand.list@gmail.com>,
        "hadess@hadess.net" <hadess@hadess.net>,
        "krzk@kernel.org" <krzk@kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
        "mathias.nyman@intel.com" <mathias.nyman@intel.com>,
        "michal.simek@xilinx.com" <michal.simek@xilinx.com>,
        "peter.chen@kernel.org" <peter.chen@kernel.org>,
        "ravisadineni@chromium.org" <ravisadineni@chromium.org>,
        "robh+dt@kernel.org" <robh+dt@kernel.org>,
        "rogerq@kernel.org" <rogerq@kernel.org>,
        "stern@rowland.harvard.edu" <stern@rowland.harvard.edu>,
        "swboyd@chromium.org" <swboyd@chromium.org>
Subject: Re: =?utf-8?B?5Zue5aSNOiDlm57lpI0=?= =?utf-8?Q?=3A?= Re: [PATCH v20
 3/5] usb: misc: Add onboard_usb_hub driver
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On Mon, Feb 28, 2022 at 03:08:34AM +0000, Linyu Yuan (QUIC) wrote:
> > From: gregkh@linuxfoundation.org <gregkh@linuxfoundation.org>
> > Sent: Wednesday, February 23, 2022 3:56 PM
> > To: Tao Wang (Consultant) (QUIC) <quic_wat@quicinc.com>
> > Cc: mka@chromium.org; balbi@kernel.org; devicetree@vger.kernel.org;
> > dianders@chromium.org; frowand.list@gmail.com; hadess@hadess.net;
> > krzk@kernel.org; linux-kernel@vger.kernel.org; linux-usb@vger.kernel.org;
> > mathias.nyman@intel.com; michal.simek@xilinx.com;
> > peter.chen@kernel.org; ravisadineni@chromium.org; robh+dt@kernel.org;
> > rogerq@kernel.org; stern@rowland.harvard.edu; swboyd@chromium.org;
> > Linyu Yuan (QUIC) <quic_linyyuan@quicinc.com>
> > Subject: Re: 回复: 回复: Re: [PATCH v20 3/5] usb: misc: Add
> > onboard_usb_hub driver
> > 
> > On Wed, Feb 23, 2022 at 07:40:31AM +0000, Tao Wang (Consultant) (QUIC)
> > wrote:
> > > Ok, thanks your reply.
> > >
> > > Here is my question, we must modify the driver "onboard_usb_hub.c" if
> > we want to use it. But it's hard to complete because it's an opensource code.
> > 
> > I do not understand.  We do not deal with code that is not in the kernel
> > source tree, as we have no idea what is out there.  Please just submit
> > your changes to be merged into the tree and all will be fine.
> 
> Hi Greg and mka,
> 
> Let's make it clear that we are talking about once this driver is approved into usb tree,
> If we use different USB HUB which have VID/PID not defined in this driver,
> We need to update this driver.
> 
> But if we defined VID/PID in device tree(for a specific board, manufacture should know VID/PID from HUB it used),
> dynamic parsed by the driver,  then we don't need to change this driver (increase VID/PID table).

As per my earlier reply, the kernel/USB core uses the VID:PID reported
by the USB device, the compatible string in the device tree is purely
informational. That's not something that could be changed by this
driver.

And even if the VID:PID from the device tree was used: how is the
kernel supposed to know that the onboard_hub driver should be
probed for a given VID:PID from the device tree, without listing
the VID:PID (or compatible string) in the driver (which is what
you seem to seek to avoid)?