On 3/10/20 1:20 PM, Andy Shevchenko wrote:
> Compiler is not happy about using ARRAY_SIZE() in comparison to smaller type:
>
> CC drivers/tty/serial/serial_core.o
> .../serial_core.c: In function ‘uart_try_toggle_sysrq’:
> .../serial_core.c:3222:24: warning: comparison is always false due to limited range of data type [-Wtype-limits]
> 3222 | if (++port->sysrq_seq < (ARRAY_SIZE(sysrq_toggle_seq) - 1)) {
> | ^
>
> Looking at the code it appears that there is an additional weirdness,
> i.e. use ARRAY_SIZE() against simple string literal. Yes, the idea probably
> was to allow '\0' in the sequence, but it's impractical: kernel configuration
> won't accept it to begin with followed by a comment about '\0' before
> comparison in question.
>
> Drop all these by switching to strlen() and convert code accordingly.
>
> Fixes: 68af43173d3f ("serial/sysrq: Add MAGIC_SYSRQ_SERIAL_SEQUENCE")
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
Reviewed-by: Dmitry Safonov <0x7f454c46@xxxxxxxxx>
Thanks!
> ---
> drivers/tty/serial/serial_core.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
> index aec98db45406..ec3b833e9f22 100644
> --- a/drivers/tty/serial/serial_core.c
> +++ b/drivers/tty/serial/serial_core.c
> @@ -3209,7 +3209,9 @@ static DECLARE_WORK(sysrq_enable_work, uart_sysrq_on);
> */
> static bool uart_try_toggle_sysrq(struct uart_port *port, unsigned int ch)
> {
> - if (ARRAY_SIZE(sysrq_toggle_seq) <= 1)
> + int sysrq_toggle_seq_len = strlen(sysrq_toggle_seq);
> +
> + if (!sysrq_toggle_seq_len)
> return false;
>
> BUILD_BUG_ON(ARRAY_SIZE(sysrq_toggle_seq) >= U8_MAX);
> @@ -3218,8 +3220,7 @@ static bool uart_try_toggle_sysrq(struct uart_port *port, unsigned int ch)
> return false;
> }
>
> - /* Without the last \0 */
> - if (++port->sysrq_seq < (ARRAY_SIZE(sysrq_toggle_seq) - 1)) {
> + if (++port->sysrq_seq < sysrq_toggle_seq_len) {
> port->sysrq = jiffies + SYSRQ_TIMEOUT;
> return true;
> }
>
--
Dima
