linux-kernel - Re: [PATCH 3/8] tty: don't store semi-state into tty drivers

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Date:   Fri, 23 Jul 2021 18:37:06 +0200
From:   Helge Deller <deller@....de>
To:     Jiri Slaby <jslaby@...e.cz>, gregkh@...uxfoundation.org
Cc:     linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        "James E.J. Bottomley" <James.Bottomley@...senPartnership.com>,
        Chris Zankel <chris@...kel.net>,
        Max Filippov <jcmvbkbc@...il.com>,
        Laurentiu Tudor <laurentiu.tudor@....com>,
        Felipe Balbi <balbi@...nel.org>
Subject: Re: [PATCH 3/8] tty: don't store semi-state into tty drivers

On 7/23/21 9:43 AM, Jiri Slaby wrote:
> When a tty driver pointer is used as a return value of struct
> console's device() hook, don't store a semi-state into global variable
> which holds the tty driver. It could mean console::device() would return
> a bogus value. This is important esp. after the next patch where we
> switch from alloc_tty_driver to tty_alloc_driver. tty_alloc_driver
> returns ERR_PTR in case of error and that might have unexpected results
> as the code doesn't expect this.
>
> Signed-off-by: Jiri Slaby <jslaby@...e.cz>
> Cc: Geert Uytterhoeven <geert@...ux-m68k.org>
> Cc: "James E.J. Bottomley" <James.Bottomley@...senPartnership.com>
> Cc: Helge Deller <deller@....de>
> Cc: Chris Zankel <chris@...kel.net>
> Cc: Max Filippov <jcmvbkbc@...il.com>
> Cc: Laurentiu Tudor <laurentiu.tudor@....com>
> Cc: Felipe Balbi <balbi@...nel.org>
> ---
>   arch/m68k/emu/nfcon.c                  | 27 +++++++++++---------
>   arch/parisc/kernel/pdc_cons.c          | 28 +++++++++++----------
>   arch/xtensa/platforms/iss/console.c    | 33 +++++++++++++-----------
>   drivers/tty/amiserial.c                | 35 ++++++++++++++------------
>   drivers/tty/ehv_bytechan.c             | 28 ++++++++++++---------
>   drivers/tty/hvc/hvsi.c                 | 35 ++++++++++++++------------
>   drivers/usb/gadget/function/u_serial.c | 32 ++++++++++++-----------
>   7 files changed, 119 insertions(+), 99 deletions(-)
>
...

You may add:

Acked-by: Helge Deller <deller@....de>	# parisc

to the whole series (specifically patches 3, 4 and 8) regarding the parisc changes.

Thank you!
Helge

>
> diff --git a/arch/parisc/kernel/pdc_cons.c b/arch/parisc/kernel/pdc_cons.c
> index 39ccad063533..650cb01203de 100644
> --- a/arch/parisc/kernel/pdc_cons.c
> +++ b/arch/parisc/kernel/pdc_cons.c
> @@ -138,6 +138,7 @@ static struct tty_driver *pdc_console_tty_driver;
>
>   static int __init pdc_console_tty_driver_init(void)
>   {
> +	struct tty_driver *driver;
>   	int err;
>
>   	/* Check if the console driver is still registered.
> @@ -160,31 +161,32 @@ static int __init pdc_console_tty_driver_init(void)
>   	printk(KERN_INFO "The PDC console driver is still registered, removing CON_BOOT flag\n");
>   	pdc_cons.flags &= ~CON_BOOT;
>
> -	pdc_console_tty_driver = alloc_tty_driver(1);
> -
> -	if (!pdc_console_tty_driver)
> +	driver = alloc_tty_driver(1);
> +	if (!driver)
>   		return -ENOMEM;
>
>   	tty_port_init(&tty_port);
>
> -	pdc_console_tty_driver->driver_name = "pdc_cons";
> -	pdc_console_tty_driver->name = "ttyB";
> -	pdc_console_tty_driver->major = MUX_MAJOR;
> -	pdc_console_tty_driver->minor_start = 0;
> -	pdc_console_tty_driver->type = TTY_DRIVER_TYPE_SYSTEM;
> -	pdc_console_tty_driver->init_termios = tty_std_termios;
> -	pdc_console_tty_driver->flags = TTY_DRIVER_REAL_RAW |
> +	driver->driver_name = "pdc_cons";
> +	driver->name = "ttyB";
> +	driver->major = MUX_MAJOR;
> +	driver->minor_start = 0;
> +	driver->type = TTY_DRIVER_TYPE_SYSTEM;
> +	driver->init_termios = tty_std_termios;
> +	driver->flags = TTY_DRIVER_REAL_RAW |
>   		TTY_DRIVER_RESET_TERMIOS;
> -	tty_set_operations(pdc_console_tty_driver, &pdc_console_tty_ops);
> -	tty_port_link_device(&tty_port, pdc_console_tty_driver, 0);
> +	tty_set_operations(driver, &pdc_console_tty_ops);
> +	tty_port_link_device(&tty_port, driver, 0);
>
> -	err = tty_register_driver(pdc_console_tty_driver);
> +	err = tty_register_driver(driver);
>   	if (err) {
>   		printk(KERN_ERR "Unable to register the PDC console TTY driver\n");
>   		tty_port_destroy(&tty_port);
>   		return err;
>   	}
>
> +	pdc_console_tty_driver = driver;
> +
>   	return 0;
>   }
>   device_initcall(pdc_console_tty_driver_init);
...