Re: [PATCH v7 10/13] serial: sh-sci: Add support for RZ/T2H SCI

[Thierry Bultel]

Le 14/04/2025 à 10:58, Greg KH a écrit :
> On Mon, Apr 14, 2025 at 07:54:12AM +0000, Thierry Bultel wrote:
> > Hi Greg,
> >
> > > -----Original Message-----
> > > From: Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx>
> > > Sent: vendredi 11 avril 2025 16:57
> > > To: Thierry Bultel <thierry.bultel.yh@xxxxxxxxxxxxxx>
> > > Cc: thierry.bultel@xxxxxxxxxxx; linux-renesas-soc@xxxxxxxxxxxxxxx;
> > > geert@xxxxxxxxxxxxxx; Paul Barker <paul.barker.ct@xxxxxxxxxxxxxx>; Wolfram
> > > Sang <wsa+renesas@xxxxxxxxxxxxxxxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx;
> > > linux-serial@xxxxxxxxxxxxxxx
> > > Subject: Re: [PATCH v7 10/13] serial: sh-sci: Add support for RZ/T2H SCI
> > >
> > > On Thu, Apr 03, 2025 at 11:29:12PM +0200, Thierry Bultel wrote:
> > > > --- a/include/uapi/linux/serial_core.h
> > > > +++ b/include/uapi/linux/serial_core.h
> > > > @@ -231,6 +231,9 @@
> > > >   /* Sunplus UART */
> > > >   #define PORT_SUNPLUS	123
> > > >
> > > > +/* SH-SCI */
> > > > +#define PORT_RSCI	124
> > > Why do you need to tell userspace about this specific port?  Is that a
> > > hard requirement that your userspace tools require?  If not, please don't
> > > export this here.
> > This point has been discussed with Geert and Wolfram.
> > We cannot use PORT_GENERIC for this IP, and adding the new type
> > is just keeping consistent with the sh-sci driver.
> But, why does userspace need to know this number?  And why doesn't
> PORT_GENERIC work?

The reason is that the sh-sci driver discriminates internally between 
port types.
There are number of locations when it checks for PORT_SCI, PORT_SCIF, 
PORT_SCIFA...
T2H SCI needs special handling, too, that is the reason why PORT_GENERIC 
cannot work. I just therefore added this new type.

> thanks,
>
> greg k-h