linux-kernel - Re: [PATCH 1/2] serial: 8250: Allow port registration without UPF_BOOT

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Message-ID: <20190426143946.GX9224@smile.fi.intel.com>
Date:   Fri, 26 Apr 2019 17:39:46 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Esben Haabendal <esben@...nix.com>
Cc:     linux-serial@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>,
        Darwin Dingel <darwin.dingel@...iedtelesis.co.nz>,
        He Zhe <zhe.he@...driver.com>,
        Jisheng Zhang <Jisheng.Zhang@...aptics.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] serial: 8250: Allow port registration without
 UPF_BOOT_AUTOCONF

On Fri, Apr 26, 2019 at 10:40:37AM +0200, Esben Haabendal wrote:
> With serial8250_register_8250_port() forcing UPF_BOOT_AUTOCONF bit on, it
> is not possible to register a port without having
> serial8250_request_std_resource() called.
> 
> For adding a 8250 port to an MFD device, this is problematic, as the
> request_mem_region() call will fail, as the MFD device (and rightly  so)
> has requested the region.  For this case, the 8250 port should accept
> having passed mapbase and membase, and just use that.

You need to simple set port type and use UPF_FIXED_TYPE.
No need for this patch.

> 
> Signed-off-by: Esben Haabendal <esben@...nix.com>
> ---
>  drivers/tty/serial/8250/8250_core.c | 36 +++++++++++++++++++++---------------
>  include/linux/serial_8250.h         |  2 ++
>  2 files changed, 23 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
> index e441221..ddbb0a0 100644
> --- a/drivers/tty/serial/8250/8250_core.c
> +++ b/drivers/tty/serial/8250/8250_core.c
> @@ -957,20 +957,8 @@ static void serial_8250_overrun_backoff_work(struct work_struct *work)
>  	spin_unlock_irqrestore(&port->lock, flags);
>  }
>  
> -/**
> - *	serial8250_register_8250_port - register a serial port
> - *	@up: serial port template
> - *
> - *	Configure the serial port specified by the request. If the
> - *	port exists and is in use, it is hung up and unregistered
> - *	first.
> - *
> - *	The port is then probed and if necessary the IRQ is autodetected
> - *	If this fails an error is returned.
> - *
> - *	On success the port is ready to use and the line number is returned.
> - */
> -int serial8250_register_8250_port(struct uart_8250_port *up)
> +int __serial8250_register_8250_port(struct uart_8250_port *up,
> +				    unsigned int extra_flags)
>  {
>  	struct uart_8250_port *uart;
>  	int ret = -ENOSPC;
> @@ -993,7 +981,7 @@ int serial8250_register_8250_port(struct uart_8250_port *up)
>  		uart->port.fifosize     = up->port.fifosize;
>  		uart->port.regshift     = up->port.regshift;
>  		uart->port.iotype       = up->port.iotype;
> -		uart->port.flags        = up->port.flags | UPF_BOOT_AUTOCONF;
> +		uart->port.flags        = up->port.flags | extra_flags;
>  		uart->bugs		= up->bugs;
>  		uart->port.mapbase      = up->port.mapbase;
>  		uart->port.mapsize      = up->port.mapsize;
> @@ -1086,6 +1074,24 @@ int serial8250_register_8250_port(struct uart_8250_port *up)
>  
>  	return ret;
>  }
> +
> +/**
> + *	serial8250_register_8250_port - register a serial port
> + *	@up: serial port template
> + *
> + *	Configure the serial port specified by the request. If the
> + *	port exists and is in use, it is hung up and unregistered
> + *	first.
> + *
> + *	The port is then probed and if necessary the IRQ is autodetected
> + *	If this fails an error is returned.
> + *
> + *	On success the port is ready to use and the line number is returned.
> + */
> +int serial8250_register_8250_port(struct uart_8250_port *up)
> +{
> +	return __serial8250_register_8250_port(up, UPF_BOOT_AUTOCONF);
> +}
>  EXPORT_SYMBOL(serial8250_register_8250_port);
>  
>  /**
> diff --git a/include/linux/serial_8250.h b/include/linux/serial_8250.h
> index 5a655ba..9d1fe2e 100644
> --- a/include/linux/serial_8250.h
> +++ b/include/linux/serial_8250.h
> @@ -145,6 +145,8 @@ static inline struct uart_8250_port *up_to_u8250p(struct uart_port *up)
>  	return container_of(up, struct uart_8250_port, port);
>  }
>  
> +extern int __serial8250_register_8250_port(struct uart_8250_port *,
> +					   unsigned int);
>  int serial8250_register_8250_port(struct uart_8250_port *);
>  void serial8250_unregister_port(int line);
>  void serial8250_suspend_port(int line);
> -- 
> 2.4.11
> 

-- 
With Best Regards,
Andy Shevchenko