Re: [PATCH 1/4] dt-bindings: usb: Document ST UCPD

[Fabrice Gasnier <fabrice.gasnier@foss.st.com>]

On 8/22/26 06:51, Marek Vasut wrote:
> On 8/21/26 6:27 PM, Fabrice Gasnier wrote:
>> On 8/19/26 18:33, Marek Vasut wrote:
>>> Document ST UCPD Type-C block. The UCPD integrates the physical
>>> layer of the Power Delivery (PD), with CC signaling method, for
>>> operation with Type-C cables. Vbus and Vconn control is performed
>>> using an external chip, usually ST TCPP01/TCPP02/TCPP03 or similar.
>>
>> Hi Marek, All,
>>
>> I've sent a series for the complete case. Please check and review here:
>> https://lore.kernel.org/linux-usb/20260821-ucpd-host-fusb340-v7-2-rfc-
>> v1-0-c5e27cbc0795@foss.st.com/
> 
> What is the difference between this driver and the ^ driver ?
> 

Hello Marek,

That includes the TCCP I2C driver (and an example on ST boards).

> Why is this driver not covering "the complete case" , what is missing
> here and not missing there ?

I intended to show a complete case, e.g. UCPD controller driver and
external TCPP I2C protection chip driver. The TCPP is a companion,
complementary, e.g. provider/consumer relationship.

You've pointed some "horribleness" there. I guess you talk about the
straight forward approach e.g. EXPORT_SYMBOL() macros. That's an
on-going work, a prototype. I could have sent as an RFC.
I wanted to be transparent, so the correct level of APIs gets used.

You propose to turn the TCPP into a GPIO chip ?
That seems smart, at least for the CC lines switches.
What about Vbus and Vconn, it could also fit regulator API ?

There are various functions, the bindings should be extensible enough
for later use of additional functions. I'm thinking of:
- Over-current events for Vbus & Vconn
  Could be represented as interrupt controller ?
  Or could benefit from a regulator notifier (if used) ?
- Vbus sensing

My point is that, that can impact the dt-bindings or functionality.
Sending UCPD driver only, without the TCCP binding & driver, I find it
is a bit hard to review or test at my end without having a more complete
view.

I'm not sure which way you'd like to proceed ?

Best Regards,
Fabrice