linux-kernel - RE: [PATCH] tty: serial: fsl_lpuart: increase maximum uart

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Message-ID:
 <DB9PR04MB842950C5700AEE30968FA1CC92102@DB9PR04MB8429.eurprd04.prod.outlook.com>
Date: Mon, 6 Jan 2025 10:24:52 +0000
From: Sherry Sun <sherry.sun@....com>
To: Greg KH <gregkh@...uxfoundation.org>
CC: "jirislaby@...nel.org" <jirislaby@...nel.org>,
	"linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"imx@...ts.linux.dev" <imx@...ts.linux.dev>
Subject: RE: [PATCH] tty: serial: fsl_lpuart: increase maximum uart_nr to 12



> -----Original Message-----
> From: Greg KH <gregkh@...uxfoundation.org>
> Sent: Friday, January 3, 2025 5:08 PM
> To: Sherry Sun <sherry.sun@....com>
> Cc: jirislaby@...nel.org; linux-serial@...r.kernel.org; linux-
> kernel@...r.kernel.org; imx@...ts.linux.dev
> Subject: Re: [PATCH] tty: serial: fsl_lpuart: increase maximum uart_nr to 12
> 
> On Fri, Jan 03, 2025 at 03:11:54PM +0800, Sherry Sun wrote:
> > Some SoCs like the i.MX943 have aliases for up to 12 UARTs, need to
> > increase UART_NR from 8 to 12 to support lpuart9-12 to avoid
> > initialization failures.
> >
> > Signed-off-by: Sherry Sun <sherry.sun@....com>
> > ---
> >  drivers/tty/serial/fsl_lpuart.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/tty/serial/fsl_lpuart.c
> > b/drivers/tty/serial/fsl_lpuart.c index 57b0632a3db6..7cb1e36fdaab
> > 100644
> > --- a/drivers/tty/serial/fsl_lpuart.c
> > +++ b/drivers/tty/serial/fsl_lpuart.c
> > @@ -245,7 +245,7 @@
> >
> >  #define DRIVER_NAME	"fsl-lpuart"
> >  #define DEV_NAME	"ttyLP"
> > -#define UART_NR		8
> > +#define UART_NR		12
> 
> Why not fix this properly and make this dynamic and get rid of the static array
> causing all of this problem?  That way when you get a system with 13 uarts,
> you will be ok :)
> 

Hi Greg,

Thanks for your comment.
But I checked all the uart drivers under drivers/tty/serial/, UART_NR is widely used, currently almost every uart driver that supports multiple uart ports defines this macro, this value is needed for the nr parameter of struct uart_driver, also for console index checking and setup.
This patch just refers to many other uart driver patches to extend maximum uart number, such as https://lore.kernel.org/all/20240112095300.2004878-3-valentin.caron@foss.st.com/.
Agree that it will be nice to dynamically allocate everything, but for now I prefer to simply change this value as there doesn't seem to be a good uart implementation at the moment, not sure what you prefer?  :)

Best Regards
Sherry