Re: [PATCH v8 1/2] Serial: silabs si4455 serial driver

['Greg Kroah-Hartman' <gregkh@linuxfoundation.org>]

On Tue, Jan 12, 2021 at 03:43:22PM +0000, József Horváth wrote:
> On Tue, Jan 12, 2021 at 11:28:08AM +0100, 'Greg Kroah-Hartman' wrote:
> > On Tue, Jan 12, 2021 at 10:18:33AM +0000, Jozsef Horvath wrote:
> > > --- a/include/uapi/linux/serial_core.h
> > > +++ b/include/uapi/linux/serial_core.h
> > > @@ -279,4 +279,7 @@
> > >  /* Freescale LINFlexD UART */
> > >  #define PORT_LINFLEXUART	122
> > >  
> > > +/* Silicon Labs SI4455 */
> > > +#define PORT_SI4455     123
> > 
> > What userspace tool is going to need this value?
> 
> The PORT_SI4455 is defined for using as port type value in struct uart_port.
> I checked other serial drivers under drivers/tty/serial and the port types
> used by serial drivers are defined in two places:
> 
> include/uapi/linux/serial_core.h
> include/uapi/linux/serial.h
> 
> The port type is required by serial_core, and its value goes back to
> user space with TIOCGSERIAL ioctl call.

What is it required for?  Who uses this?

> I can't set port type value to 0(PORT_UNKNOWN).

Why not?

> I think my drivers source is not the best place to defining PORT_SI4455,
>  but I can't find better place then include/uapi/linux/serial_core.h
> 
> Could you please help me where is the correct location for this definition?

I ask as I am trying to figure out why we keep adding these ids, yet no
tool that i know of seems to actually use them.

If you don't have a tool that needs to use a new id, then I would
recommend not adding it, right?

thanks,

greg k-h