2021-09-17 06:21:10

by Nathan Chancellor

Subject: [PATCH] ptp: ocp: Avoid operator precedence warning in ptp_ocp_summary_show()

Clang warns twice:

drivers/ptp/ptp_ocp.c:2065:16: error: operator '?:' has lower precedence
than '&'; '&' will be evaluated first
[-Werror,-Wbitwise-conditional-parentheses]
on & map ? " ON" : "OFF", src);
~~~~~~~~ ^
drivers/ptp/ptp_ocp.c:2065:16: note: place parentheses around the '&'
expression to silence this warning
on & map ? " ON" : "OFF", src);
^
( )
drivers/ptp/ptp_ocp.c:2065:16: note: place parentheses around the '?:'
expression to evaluate it first
on & map ? " ON" : "OFF", src);
^

It is clearly intentional that the bitwise operation be done before the
ternary operation so add the parentheses as it suggests to fix the
warning.

Fixes: a62a56d04e63 ("ptp: ocp: Enable 4th timestamper / PPS generator")
Link: https://github.com/ClangBuiltLinux/linux/issues/1457
Signed-off-by: Nathan Chancellor <[email protected]>
---
drivers/ptp/ptp_ocp.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/ptp/ptp_ocp.c b/drivers/ptp/ptp_ocp.c
index 844b1401cc5d..4ba3fb254a92 100644
--- a/drivers/ptp/ptp_ocp.c
+++ b/drivers/ptp/ptp_ocp.c
@@ -2062,11 +2062,11 @@ ptp_ocp_summary_show(struct seq_file *s, void *data)
on = ioread32(&ts_reg->enable);
map = !!(bp->pps_req_map & OCP_REQ_TIMESTAMP);
seq_printf(s, "%7s: %s, src: %s\n", "TS3",
- on & map ? " ON" : "OFF", src);
+ (on & map) ? " ON" : "OFF", src);

map = !!(bp->pps_req_map & OCP_REQ_PPS);
seq_printf(s, "%7s: %s, src: %s\n", "PPS",
- on & map ? " ON" : "OFF", src);
+ (on & map) ? " ON" : "OFF", src);
}

if (bp->irig_out) {

base-commit: 4b5a3ab17c6c942bd428984b6b37fe3c07f18ab3
--
2.33.0

2021-09-17 12:22:24

by Jonathan Lemon

Subject: Re: [PATCH] ptp: ocp: Avoid operator precedence warning in ptp_ocp_summary_show()

On Thu, Sep 16, 2021 at 12:43:51PM -0700, Nathan Chancellor wrote:
> Clang warns twice:
>
> drivers/ptp/ptp_ocp.c:2065:16: error: operator '?:' has lower precedence
> than '&'; '&' will be evaluated first
> [-Werror,-Wbitwise-conditional-parentheses]
> on & map ? " ON" : "OFF", src);
> ~~~~~~~~ ^
> drivers/ptp/ptp_ocp.c:2065:16: note: place parentheses around the '&'
> expression to silence this warning
> on & map ? " ON" : "OFF", src);
> ^
> ( )
> drivers/ptp/ptp_ocp.c:2065:16: note: place parentheses around the '?:'
> expression to evaluate it first
> on & map ? " ON" : "OFF", src);
> ^
>
> It is clearly intentional that the bitwise operation be done before the
> ternary operation so add the parentheses as it suggests to fix the
> warning.

Actually, the correct fix is to change '&' to '&&', so a logical
operation is done instead of an arithmetic operation. I believe
this will silence the warning from clang.
--
Jonathan