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From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Lukas Wunner <lukas@wunner.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Jiri Slaby <jslaby@suse.com>,
	"Matwey V. Kornilov" <matwey@sai.msu.ru>,
	Giulio Benetti <giulio.benetti@micronovasrl.com>,
	Heiko Stuebner <heiko@sntech.de>,
	Christoph Muellner <christoph.muellner@theobroma-systems.com>,
	linux-serial@vger.kernel.org
Subject: Re: [PATCH v2 1/4] serial: 8250: Avoid error message on reprobe
Date: Tue, 12 May 2020 16:45:45 +0300	[thread overview]
Message-ID: <20200512134545.GZ185537@smile.fi.intel.com> (raw)
In-Reply-To: <b4a072013ee1a1d13ee06b4325afb19bda57ca1b.1589285873.git.lukas@wunner.de>

On Tue, May 12, 2020 at 02:40:01PM +0200, Lukas Wunner wrote:
> If the call to uart_add_one_port() in serial8250_register_8250_port()
> fails, a half-initialized entry in the serial_8250ports[] array is left
> behind.
> 
> A subsequent reprobe of the same serial port causes that entry to be
> reused.  Because uart->port.dev is set, uart_remove_one_port() is called
> for the half-initialized entry and bails out with an error message:
> 
> bcm2835-aux-uart 3f215040.serial: Removing wrong port: (null) != (ptrval)
> 
> The same happens on failure of mctrl_gpio_init() since commit
> 4a96895f74c9 ("tty/serial/8250: use mctrl_gpio helpers").
> 
> Fix by zeroing the uart->port.dev pointer in the probe error path.
> 
> The bug was introduced in v2.6.10 by historical commit befff6f5bf5f
> ("[SERIAL] Add new port registration/unregistration functions."):
> https://git.kernel.org/tglx/history/c/befff6f5bf5f
> 
> The commit added an unconditional call to uart_remove_one_port() in
> serial8250_register_port().  In v3.7, commit 835d844d1a28 ("8250_pnp:
> do pnp probe before legacy probe") made that call conditional on
> uart->port.dev which allows me to fix the issue by zeroing that pointer
> in the error path.  Thus, the present commit will fix the problem as far
> back as v3.7 whereas still older versions need to also cherry-pick
> 835d844d1a28.

Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

> Fixes: 835d844d1a28 ("8250_pnp: do pnp probe before legacy probe")
> Signed-off-by: Lukas Wunner <lukas@wunner.de>
> Cc: stable@vger.kernel.org # v2.6.10
> Cc: stable@vger.kernel.org # v2.6.10: 835d844d1a28: 8250_pnp: do pnp probe before legacy
> ---
> Changes v1 -> v2:
> * Drop unnecessary "else" after "if ... goto" statement. (Andy)
> * Document applicability to older kernels in commit message. (Andy)
> * Add Fixes tag. (Andy)
> 
>  drivers/tty/serial/8250/8250_core.c | 14 ++++++++++----
>  1 file changed, 10 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
> index 45d9117cab68..9548d3f8fc8e 100644
> --- a/drivers/tty/serial/8250/8250_core.c
> +++ b/drivers/tty/serial/8250/8250_core.c
> @@ -1040,7 +1040,7 @@ int serial8250_register_8250_port(struct uart_8250_port *up)
>  			gpios = mctrl_gpio_init(&uart->port, 0);
>  			if (IS_ERR(gpios)) {
>  				ret = PTR_ERR(gpios);
> -				goto out_unlock;
> +				goto err;
>  			} else {
>  				uart->gpios = gpios;
>  			}
> @@ -1089,8 +1089,10 @@ int serial8250_register_8250_port(struct uart_8250_port *up)
>  			serial8250_apply_quirks(uart);
>  			ret = uart_add_one_port(&serial8250_reg,
>  						&uart->port);
> -			if (ret == 0)
> -				ret = uart->port.line;
> +			if (ret)
> +				goto err;
> +
> +			ret = uart->port.line;
>  		} else {
>  			dev_info(uart->port.dev,
>  				"skipping CIR port at 0x%lx / 0x%llx, IRQ %d\n",
> @@ -1112,10 +1114,14 @@ int serial8250_register_8250_port(struct uart_8250_port *up)
>  		}
>  	}
>  
> -out_unlock:
>  	mutex_unlock(&serial_mutex);
>  
>  	return ret;
> +
> +err:
> +	uart->port.dev = NULL;
> +	mutex_unlock(&serial_mutex);
> +	return ret;
>  }
>  EXPORT_SYMBOL(serial8250_register_8250_port);
>  
> -- 
> 2.26.2
> 

-- 
With Best Regards,
Andy Shevchenko



  reply	other threads:[~2020-05-12 13:45 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-12 12:40 [PATCH v2 0/4] rs485 bus termination GPIO Lukas Wunner
2020-05-12 12:40 ` [PATCH v2 1/4] serial: 8250: Avoid error message on reprobe Lukas Wunner
2020-05-12 13:45   ` Andy Shevchenko [this message]
2020-05-12 12:40 ` [PATCH v2 2/4] serial: Allow uart_get_rs485_mode() to return errno Lukas Wunner
2020-05-12 13:46   ` Andy Shevchenko
2020-05-12 12:40 ` [PATCH v2 3/4] dt-bindings: serial: Add binding for rs485 bus termination GPIO Lukas Wunner
2020-05-12 12:40 ` [PATCH v2 4/4] serial: 8250: Support " Lukas Wunner
2020-05-12 14:09   ` Andy Shevchenko

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