| Message ID | 20190810044910.114015-1-natechancellor@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | firmware: arm_scmi: Eliminate local db variable in SCMI_PERF_FC_RING_DB | expand |
On Fri, Aug 09, 2019 at 09:49:10PM -0700, Nathan Chancellor wrote: > clang warns four times: > > drivers/firmware/arm_scmi/perf.c:320:24: warning: variable 'db' is > uninitialized when used within its own initialization [-Wuninitialized] > SCMI_PERF_FC_RING_DB(db, 64); > ~~~~~~~~~~~~~~~~~~~~~^~~~~~~ > drivers/firmware/arm_scmi/perf.c:300:31: note: expanded from macro > 'SCMI_PERF_FC_RING_DB' > struct scmi_fc_db_info *db = doorbell; \ > ~~ ^~~~~~~~ > > This happens because the doorbell identifier becomes db after > preprocessing: > > if (db->width == 1) > do { > u8 val = 0; > struct scmi_fc_db_info *db = db; > if (db->mask) > val = ioread8(db->addr) & db->mask; > iowrite8((u8)db->set | val, db->addr); > } while (0); > > We could swap the doorbell and db identifiers within the macro and that > would resolve the issue; however, there doesn't appear to be a good > reason for having two copies of the same variable. Eliminate the one in > the do while loop to prevent this warning and make the code clearer. > I originally had exactly what we will after this patch applied. I think one of the tool complained about argument 'db' reused in the macro might have possible side-effects. That's the reason I moved it. I will dig it up and fold this in the original patch as before. -- Regards, Sudeep
diff --git a/drivers/firmware/arm_scmi/perf.c b/drivers/firmware/arm_scmi/perf.c index 2c5201c8354c..ab946ef6b914 100644 --- a/drivers/firmware/arm_scmi/perf.c +++ b/drivers/firmware/arm_scmi/perf.c @@ -294,10 +294,9 @@ scmi_perf_describe_levels_get(const struct scmi_handle *handle, u32 domain, return ret; } -#define SCMI_PERF_FC_RING_DB(doorbell, w) \ +#define SCMI_PERF_FC_RING_DB(db, w) \ do { \ u##w val = 0; \ - struct scmi_fc_db_info *db = doorbell; \ \ if (db->mask) \ val = ioread##w(db->addr) & db->mask; \
clang warns four times: drivers/firmware/arm_scmi/perf.c:320:24: warning: variable 'db' is uninitialized when used within its own initialization [-Wuninitialized] SCMI_PERF_FC_RING_DB(db, 64); ~~~~~~~~~~~~~~~~~~~~~^~~~~~~ drivers/firmware/arm_scmi/perf.c:300:31: note: expanded from macro 'SCMI_PERF_FC_RING_DB' struct scmi_fc_db_info *db = doorbell; \ ~~ ^~~~~~~~ This happens because the doorbell identifier becomes db after preprocessing: if (db->width == 1) do { u8 val = 0; struct scmi_fc_db_info *db = db; if (db->mask) val = ioread8(db->addr) & db->mask; iowrite8((u8)db->set | val, db->addr); } while (0); We could swap the doorbell and db identifiers within the macro and that would resolve the issue; however, there doesn't appear to be a good reason for having two copies of the same variable. Eliminate the one in the do while loop to prevent this warning and make the code clearer. Fixes: 8f12cbcb6abc ("firmware: arm_scmi: Make use SCMI v2.0 fastchannel for performance protocol") Link: https://github.com/ClangBuiltLinux/linux/issues/635 Signed-off-by: Nathan Chancellor <natechancellor@gmail.com> --- drivers/firmware/arm_scmi/perf.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)