Subject: USB Type-C Port Manager API concern
To: Guenter Roeck <linux@roeck-us.net>
References: <20170221142405.76299-1-heikki.krogerus@linux.intel.com>
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 <07618170-d561-e7fe-08e0-91316c53d832@gmail.com>
 <20170303125940.GA6999@kuha.fi.intel.com>
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 <696552a7-c36a-1d73-9517-543907e9da39@gmail.com>
 <9b32fabf-3ff5-112f-4249-a7024f808b20@roeck-us.net>
Cc: Heikki Krogerus <heikki.krogerus@linux.intel.com>,
        Greg KH <gregkh@linuxfoundation.org>,
        Felipe Balbi <felipe.balbi@linux.intel.com>,
        linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org
From: Mats Karrman <mats.dev.list@gmail.com>
Message-ID: <4fe455d8-30d9-0c21-46aa-6d273cd24d50@gmail.com>
Date: Sun, 9 Apr 2017 01:09:57 +0200
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Hi Guenter,

 From a previous thread:

On 03/08/2017 02:38 AM, Guenter Roeck wrote:
> On 03/07/2017 02:30 PM, Mats Karrman wrote:
> [ ... ]
>
>>
>> I'm still struggling to catch up on what you guys have been up to 
>> during the
>> last year or so :-) and came across some patches of Guenter from last 
>> October:
>>
>> http://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1243527.html
>>
>> What happened to them? Has there been any progress since then?
>>
>
> Updates to keep in sync with API changes, bug fixes, and minor 
> improvements,
> for the most part. I can post a current version if there is interest.
> The latest version is also available from
> https://chromium-review.googlesource.com/#/c/389917/

I'm working on a tcpi driver and have some concern about the tcpm api.
The tcpm_register_port() is typically called from the probe function of
tcpi driver where the tcpm_port reference returned is stored in the
driver private data. The problem I ran into is that tcpm_register_port()
calls back to the not yet fully initialized tcpi driver, causing null-
pointer dereferences. This could of course be solved by extra logic in
the tcpi driver but I think it would be more elegant if the registration
of a port could be free of premature callbacks. E.g. it could be required
that the tcpi driver probe called tcpm_tcpc_reset() once it's done
initializing or the necessary data could be supplied in the call to
tcpm_register_port().
What do you think?

BR,
Mats