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

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Message-ID: <eba16d9a-9e07-498f-a7ab-0bb36076de40@linatsea.fr>
Date: Mon, 14 Apr 2025 11:23:34 +0200
From: Thierry Bultel <thierry.bultel@...atsea.fr>
To: Greg KH <gregkh@...uxfoundation.org>,
 Thierry Bultel <thierry.bultel.yh@...renesas.com>
Cc: "linux-renesas-soc@...r.kernel.org" <linux-renesas-soc@...r.kernel.org>,
 "geert@...ux-m68k.org" <geert@...ux-m68k.org>,
 Paul Barker <paul.barker.ct@...renesas.com>,
 Wolfram Sang <wsa+renesas@...g-engineering.com>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>
Subject: Re: [PATCH v7 10/13] serial: sh-sci: Add support for RZ/T2H SCI



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@...uxfoundation.org>
>>> Sent: vendredi 11 avril 2025 16:57
>>> To: Thierry Bultel <thierry.bultel.yh@...renesas.com>
>>> Cc: thierry.bultel@...atsea.fr; linux-renesas-soc@...r.kernel.org;
>>> geert@...ux-m68k.org; Paul Barker <paul.barker.ct@...renesas.com>; Wolfram
>>> Sang <wsa+renesas@...g-engineering.com>; linux-kernel@...r.kernel.org;
>>> linux-serial@...r.kernel.org
>>> 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