linux-kernel - Re: [PATCH v3] usb: dwc3: qcom: Remove extcon functionality from glue

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Message-ID: <arp6ujd3463lzrpi77e6sb5mwie3uzsyzildct3hkgkni7ozfb@zxomg4beii2b>
Date: Tue, 15 Jul 2025 21:01:59 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Krishna Kurapati <krishna.kurapati@....qualcomm.com>,
        Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        Bjorn Andersson <bjorn.andersson@....qualcomm.com>,
        linux-arm-msm@...r.kernel.org, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] usb: dwc3: qcom: Remove extcon functionality from glue

On Tue, Jul 15, 2025 at 07:47:20PM +0200, Greg Kroah-Hartman wrote:
> On Mon, Jul 14, 2025 at 10:17:02AM +0530, Krishna Kurapati wrote:
> > Deprecate usage of extcon functionality from the glue driver. Now
> > that the glue driver is a flattened implementation, all existing
> > DTs would eventually move to new bindings. While doing so let them
> > make use of role-switch/ typec frameworks to provide role data
> > rather than using extcon.
> 
> "Deprecate"?  Looks like you are just deleting all of this code, what is
> going to break when this is removed?  Are there any in-kernel users of
> it?
> 
> > On upstream, summary of targets/platforms using extcon is as follows:
> > 
> > 1. MSM8916 and MSM8939 use Chipidea controller, hence the changes have no
> > effect on them.
> 
> Ok, so those are fine, but:
> 
> > 2. Of the other extcon users, most of them use "linux,extcon-usb-gpio"
> > driver which relies on id/vbus gpios to inform role changes. This can be
> > transitioned to role switch based driver (usb-conn-gpio) while flattening
> > those platforms to move away from extcon and rely on role
> > switching.
> 
> When is that going to happen?  Where are those patches?

This should be better explained in the commit message, I agree here.

Krishna, please point out that existing extcon platforms use legacy glue
driver (due to using legacy DT bindings), while this patch touches only
the new ("flattened") DWC3 driver.

> 
> > 3. The one target that uses dwc3 controller and extcon and is not based
> > on reading gpios is "arch/arm64/boot/dts/qcom/msm8996-xiaomi-common.dtsi".
> > This platform uses TI chip to provide extcon. If usb on this platform is
> > being flattneed, then effort should be put in to define a usb-c-connector
> > device in DT and make use of role switch functionality in TUSB320L driver.
> 
> Again, when is that going to be changed?  We can't break in-kernel users
> :(
> 
> thanks,
> 
> greg k-h

-- 
With best wishes
Dmitry