linux-kernel - Re: [PATCH v4 09/18] usb: dwc3: qcom: Override VBUS when using gpio_usb

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Message-ID: <453bfea7-4085-1a24-84ad-30c7671665e7@linaro.org>
Date:   Fri, 7 Feb 2020 10:50:45 +0000
From:   Bryan O'Donoghue <bryan.odonoghue@...aro.org>
To:     Jack Pham <jackp@...eaurora.org>
Cc:     linux-arm-msm@...r.kernel.org, linux-usb@...r.kernel.org,
        gregkh@...uxfoundation.org, balbi@...nel.org,
        bjorn.andersson@...aro.org, linux-kernel@...r.kernel.org,
        Andy Gross <agross@...nel.org>,
        Lee Jones <lee.jones@...aro.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Manu Gautam <mgautam@...eaurora.org>
Subject: Re: [PATCH v4 09/18] usb: dwc3: qcom: Override VBUS when using
 gpio_usb_connector

On 07/02/2020 10:36, Bryan O'Donoghue wrote:
> On 07/02/2020 08:07, Jack Pham wrote:
>> Could the usb_role_switch class somehow be enhanced to support chaining
>> multiple "consumers" to support this case? Such that when the gpio-b
>> driver calls set_role() it could get handled both by drd.c and
>> dwc3-qcom.c?
> 
> It is probably necessary eventually, but, per my reading of the 
> documents and working with the hardware, I couldn't justify the 
> additional work.
> 
> However if you think this patchset needs the toggle, I can look into 
> getting the indicator to toggle here too.
> 
> We'd need to add some sort of linked list of notifiers to the role 
> switching logic and toggle them in order.
> 
> Similar to what is done in extcon now for the various notifer hooks.

Maybe I'm wrong...

Looking a bit closer at the role-switch code it might be possible to 
register multiple devices _as-is_ so long as you have a pointer to the 
relevant parent...

---
bod