linux-kernel - Re: [PATCH] USB TYPEC: RT1711H Type-C Chip Driver

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Message-ID: <20180122185034.GA26058@roeck-us.net>
Date:   Mon, 22 Jan 2018 10:50:34 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     shufan_lee(李書帆) <shufan_lee@...htek.com>
Cc:     Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        'Jun Li' <jun.li@....com>, ShuFanLee <leechu729@...il.com>,
        cy_huang(黃啟原) <cy_huang@...htek.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>
Subject: Re: [PATCH] USB TYPEC: RT1711H Type-C Chip Driver

On Mon, Jan 22, 2018 at 02:01:13AM +0000, shufan_lee(李書帆) wrote:
> Dear Heikki and Guenter,
> 
>   Because there are still other controls of RT1711H that are different from standard TCPCI, e.x. flow of drp toggling.
> 
>   Is the suggestion to customize the difference based on tcpci.c for RT1711H?
> 

In general, I would say yes. However, I won't have ime to review 
the differences between tcpci and the RT1711H. On a high level,
if RT1711H claims to suport TCPCI, it should use (or, rather, extend)
the TCPCI driver.

Note that the TCPCI driver does not claim to be complete; there is
a reason why it is still in staging. However, I would prefer if new
devices claiming to support TCPCI would use it instead of going
their own way. I don't have problems extending it with chip specific
details if needed. Such extensions may be implemented in tcpci.c,
or maybe better in a chip specific file.

Even if you don't use the existing driver, I don't really see why
it would make sense to redeclare all its defines.

Either case, you might want to run checkpatch --strict on your
driver. Most of that it reports is really unnecessary.
Also, some of the code, such as

+#ifndef BIT
+#define BIT(x) (1 << (x))
+#endif

is _really_ odd and, at least in this case, simply wrong.

Guenter

> Best Regards,
> *****************************
> Shu-Fan Lee
> Richtek Technology Corporation
> TEL: +886-3-5526789 #2359
> FAX: +886-3-5526612
> *****************************
> 
> -----Original Message-----
> From: Guenter Roeck [mailto:groeck7@...il.com] On Behalf Of Guenter Roeck
> Sent: Saturday, January 20, 2018 12:03 AM
> To: Heikki Krogerus
> Cc: shufan_lee(李書帆); 'Jun Li'; ShuFanLee; cy_huang(黃啟原); linux-kernel@...r.kernel.org; linux-usb@...r.kernel.org
> Subject: Re: [PATCH] USB TYPEC: RT1711H Type-C Chip Driver
> 
> On Fri, Jan 19, 2018 at 11:24:13AM +0200, Heikki Krogerus wrote:
> > Hi,
> >
> > On Fri, Jan 19, 2018 at 09:01:24AM +0000, shufan_lee(?????|) wrote:
> > > Hi Heikki,
> > >
> > >   For example, the flow of tcpci_init is a little bit different.
> > >   In tcpci_init, there are more parameters need to be set for RT1711H.
> >
> > Different init parameters is really not a reason for a fork of the
> > driver. The configuration of the TCPC will depend on the platform and
> > TCPC vendor most cases.
> >
> Agreed. dwc3 usb support is an excellent example on how to handle this kind of variation.
> 
> Guenter
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