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From:   Stefan-gabriel Mirea <stefan-gabriel.mirea@nxp.com>
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Subject: Re: [PATCH 5/6] tty: serial: Add linflexuart driver for S32V234
Thread-Topic: [PATCH 5/6] tty: serial: Add linflexuart driver for S32V234
Thread-Index: AQHVTT8SPpHUwU0eqkG6Gc3hvK3zpw==
Date:   Wed, 7 Aug 2019 16:42:17 +0000
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On 8/6/2019 9:40 PM, gregkh@linuxfoundation.org wrote:=0A=
> On Tue, Aug 06, 2019 at 05:11:17PM +0000, Stefan-gabriel Mirea wrote:=0A=
>> On 8/5/2019 6:31 PM, gregkh@linuxfoundation.org wrote:=0A=
>>> On Fri, Aug 02, 2019 at 07:47:23PM +0000, Stefan-gabriel Mirea wrote:=
=0A=
>>>>=0A=
>>>> +/* Freescale Linflex UART */=0A=
>>>> +#define PORT_LINFLEXUART     121=0A=
>>>=0A=
>>> Do you really need this modified?=0A=
>>=0A=
>> Hello Greg,=0A=
>>=0A=
>> This macro is meant to be assigned to port->type in the config_port=0A=
>> method from uart_ops, in order for verify_port to know if the received=
=0A=
>> serial_struct structure was really targeted for a LINFlex port. It=0A=
>> needs to be defined outside, to avoid "collisions" with other drivers.=
=0A=
> =0A=
> Yes, I know what it goes to, but does anyone in userspace actually use=0A=
> it?=0A=
=0A=
No, we do not use it from userspace, but kept the pattern only for=0A=
conformance.=0A=
=0A=
>> Other than that, I do not see anything wrong with the addition of a=0A=
>> define in serial_core.h for this purpose (which is also what most of the=
=0A=
>> serial drivers do, including amba-pl011.c, mentioned in=0A=
>> Documentation/driver-api/serial/driver.rst as providing the reference=0A=
>> implementation), so please be more specific.=0A=
> =0A=
> I am getting tired of dealing with merge issues with that list, and no=0A=
> one seems to be able to find where they are really needed for userspace,=
=0A=
> especially for new devices.  What happens if you do not have use it?=0A=
=0A=
I see. If I drop its usage completely and leave 'type' from the=0A=
uart_port as 0, uart_port_startup() will fail when finding that=0A=
uport->type =3D=3D PORT_UNKNOWN at [1] (there may be other effects as well,=
=0A=
e.g. due to the check in uart_configure_port[2]).=0A=
=0A=
So I suppose that I need to define some nonzero 'PORT_KNOWN' macro in=0A=
the driver and use that one internally for 'type'. Is my understanding=0A=
correct? Will there be any problems if I define it to a positive integer=0A=
which is already assigned to another driver, according to serial_core.h?=0A=
=0A=
Regards,=0A=
Stefan=0A=
=0A=
[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree=
/drivers/tty/serial/serial_core.c?h=3Dv5.3-rc1#n188=0A=
[2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree=
/drivers/tty/serial/serial_core.c?h=3Dv5.3-rc1#n2348=0A=