Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [PATCH-next 3/3] serial/sysrq: Add MAGIC_SYSRQ_SERIAL_SEQUENCE
To:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc:     linux-kernel@vger.kernel.org,
        Dmitry Safonov <0x7f454c46@gmail.com>,
        Jiri Slaby <jslaby@suse.com>,
        Vasiliy Khoruzhick <vasilykh@arista.com>,
        linux-serial@vger.kernel.org
References: <20200109215444.95995-1-dima@arista.com>
 <20200109215444.95995-4-dima@arista.com> <20200110164643.GB1822445@kroah.com>
 <a6a3ee46-9537-c287-b366-797c787c28b6@arista.com>
From:   Dmitry Safonov <dima@arista.com>
Message-ID: <41435a7b-48a2-438c-998a-14481fbc3a1a@arista.com>
Date:   Tue, 14 Jan 2020 19:10:47 +0000
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101
 Thunderbird/68.3.0
MIME-Version: 1.0
In-Reply-To: <a6a3ee46-9537-c287-b366-797c787c28b6@arista.com>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 1/10/20 10:32 PM, Dmitry Safonov wrote:
> On 1/10/20 4:46 PM, Greg Kroah-Hartman wrote:
> [..]
>>> diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
>>> index 6ac9dfed3423..f70eba032d0b 100644
>>> --- a/drivers/tty/serial/serial_core.c
>>> +++ b/drivers/tty/serial/serial_core.c
>>> @@ -3081,6 +3081,38 @@ void uart_insert_char(struct uart_port *port, unsigned int status,
>>>  }
>>>  EXPORT_SYMBOL_GPL(uart_insert_char);
>>>  
>>> +const char sysrq_toggle_seq[] = CONFIG_MAGIC_SYSRQ_SERIAL_SEQUENCE;
>>> +
>>> +static void uart_sysrq_on(struct work_struct *w)
>>> +{
>>> +	sysrq_toggle_support(1);
>>> +	pr_info("SysRq is enabled by magic sequience on serial\n");
>>
>> Do we want to say what serial port it is enabled on?
> 
> Makes sense, will add.

Ah, I've managed to forget to mention that I didn't add the port name
into the message in v2. I experimented a bit - it's getting a bit
complicated how-to protect (char *name) for just this message.
Like, SysRq can be theoretically enabled on two serials at the same
moment - so some locking is needed to make the printed name sane.

As sysrq_toggle_support() is a global-enable knob for sysrq (also can be
switched in /proc/sys/kernel/sysrq) I'm not sure if it's worth to
complicate code to print through which serial console SysRq has been
enabled.

I can still do it in v3 if you insist.

And sorry about forgetting to mention this - thought I'll write reply
after I send v2 and somehow it slipped my mind.

Thanks,
           Dmitry