linux-kernel - Re: 回复: 回复: Re: [PATCH v20 3/5] usb: misc: Add onboard_usb

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Message-ID: <Yh5K0u3jp4jTXCPi@google.com>
Date:   Tue, 1 Mar 2022 08:33:22 -0800
From:   "mka@...omium.org" <mka@...omium.org>
To:     "Linyu Yuan (QUIC)" <quic_linyyuan@...cinc.com>
Cc:     "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "Tao Wang (Consultant) (QUIC)" <quic_wat@...cinc.com>,
        "balbi@...nel.org" <balbi@...nel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "dianders@...omium.org" <dianders@...omium.org>,
        "frowand.list@...il.com" <frowand.list@...il.com>,
        "hadess@...ess.net" <hadess@...ess.net>,
        "krzk@...nel.org" <krzk@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "mathias.nyman@...el.com" <mathias.nyman@...el.com>,
        "michal.simek@...inx.com" <michal.simek@...inx.com>,
        "peter.chen@...nel.org" <peter.chen@...nel.org>,
        "ravisadineni@...omium.org" <ravisadineni@...omium.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "rogerq@...nel.org" <rogerq@...nel.org>,
        "stern@...land.harvard.edu" <stern@...land.harvard.edu>,
        "swboyd@...omium.org" <swboyd@...omium.org>
Subject: Re: 回复: 回复: Re: [PATCH v20
 3/5] usb: misc: Add onboard_usb_hub driver

On Tue, Mar 01, 2022 at 02:30:00AM +0000, Linyu Yuan (QUIC) wrote:
> > From: mka@...omium.org <mka@...omium.org>
> > Sent: Tuesday, March 1, 2022 2:29 AM
> > To: Linyu Yuan (QUIC) <quic_linyyuan@...cinc.com>
> > Cc: gregkh@...uxfoundation.org; Tao Wang (Consultant) (QUIC)
> > <quic_wat@...cinc.com>; balbi@...nel.org; devicetree@...r.kernel.org;
> > dianders@...omium.org; frowand.list@...il.com; hadess@...ess.net;
> > krzk@...nel.org; linux-kernel@...r.kernel.org; linux-usb@...r.kernel.org;
> > mathias.nyman@...el.com; michal.simek@...inx.com;
> > peter.chen@...nel.org; ravisadineni@...omium.org; robh+dt@...nel.org;
> > rogerq@...nel.org; stern@...land.harvard.edu; swboyd@...omium.org
> > Subject: Re: 回复: 回复: Re: [PATCH v20 3/5] usb: misc: Add
> > onboard_usb_hub driver
> > 
> > >
> > > 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.
> I can't fully understand this comment,  could you please share step if we want to add a new HUB support, what should we do ? nothing ?

Add the VID:PID and compatible strings to onboard_usb_hub.c, analogous
to those for the RTS5411 and RTS5414. More work will be needed if the
hub needs a special power up or power down sequence (multiple regulators,
GPIOs, ...)

> If do nothing, can we remove id_table from  onboard_hub_usbdev_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)?
> In my opinion, if it need update VID/PID table in this driver to support a new HUB,
> we can parse VID/PID from device tree and create dynamic VID/PID entry to id_table of onboard_hub_usbdev_driver.
> 
> Hope you can understand what I said.

Not really.

I doubt that what you are suggesting would work. The easiest thing
to convince people would probably be to send a patch (based on this
one) with a working implementation of your idea.