Re: [PATCHv2-next 2/3] serial/sysrq: Add MAGIC_SYSRQ_SERIAL_SEQUENCE

Dmitry Safonov
2020-01-14T17:37:07Z

Hi Joe,

On 1/14/20 5:30 PM, Joe Perches wrote:
> 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.

I agree. Though, somehow it seems to me that `return 1` is a bit closer
to "one character consumed" than "return true".
Again, no hard feelings, just a preference.
I can change those returns to bools if you insist :)

>
>> +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...
>
>

Thanks,
Dmitry