linux-kernel - Re: [PATCHv2-next 2/3] serial/sysrq: Add MAGIC_SYSRQ_SERIAL

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Message-ID: <24455cb643415cf9379bb8343525b844ead4236b.camel@perches.com>
Date:   Tue, 14 Jan 2020 09:30:45 -0800
From:   Joe Perches <joe@...ches.com>
To:     Dmitry Safonov <dima@...sta.com>, linux-kernel@...r.kernel.org
Cc:     Dmitry Safonov <0x7f454c46@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Iurii Zaikin <yzaikin@...gle.com>,
        Jiri Slaby <jslaby@...e.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Vasiliy Khoruzhick <vasilykh@...sta.com>,
        linux-serial@...r.kernel.org
Subject: Re: [PATCHv2-next 2/3] serial/sysrq: Add MAGIC_SYSRQ_SERIAL_SEQUENCE

On Tue, 2020-01-14 at 17:19 +0000, Dmitry Safonov wrote:
> Many embedded boards have a disconnected TTL level serial which can
> generate some garbage that can lead to spurious false sysrq detects.

Hi again Dmitry.  trivia:

> diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
[]
> +/**
> + *	uart_try_toggle_sysrq - Enables SysRq from serial line
> + *	@port: uart_port structure where char(s) after BREAK met
> + *	@ch: new character in the sequence after received BREAK
> + *
> + *	Enables magic SysRq when the required sequence is met on port
> + *	(see CONFIG_MAGIC_SYSRQ_SERIAL_SEQUENCE).
> + *
> + *	Returns 0 if @ch is out of enabling sequence and should be
> + *	handled some other way, 1 if @ch was consumed.
> + */

Normally bool functions return values are true/false not 1/0.

> +static bool uart_try_toggle_sysrq(struct uart_port *port, unsigned int ch)
> +{
> +	if (ARRAY_SIZE(sysrq_toggle_seq) <= 1)
> +		return 0;

		return false;

etc...