lkml.org 
[lkml]   [2018]   [Feb]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[PATCH v2 8/8] platform: vivid-cec: use 64-bit arithmetic instead of 32-bit
Add suffix ULL to constant 10 in order to give the compiler complete
information about the proper arithmetic to use. Notice that this
constant is used in a context that expects an expression of type
u64 (64 bits, unsigned).

The expression len * 10 * CEC_TIM_DATA_BIT_TOTAL is currently being
evaluated using 32-bit arithmetic.

Also, remove unnecessary parentheses and add a code comment to make it
clear what is the reason of the code change.

Addresses-Coverity-ID: 1454996
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
---
Changes in v2:
- Update subject and changelog to better reflect the proposed code changes.
- Add suffix ULL to constant instead of casting a variable.
- Remove unncessary parentheses.
- Add code comment.

drivers/media/platform/vivid/vivid-cec.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/media/platform/vivid/vivid-cec.c b/drivers/media/platform/vivid/vivid-cec.c
index b55d278..614787b 100644
--- a/drivers/media/platform/vivid/vivid-cec.c
+++ b/drivers/media/platform/vivid/vivid-cec.c
@@ -82,8 +82,15 @@ static void vivid_cec_pin_adap_events(struct cec_adapter *adap, ktime_t ts,

if (adap == NULL)
return;
- ts = ktime_sub_us(ts, (CEC_TIM_START_BIT_TOTAL +
- len * 10 * CEC_TIM_DATA_BIT_TOTAL));
+
+ /*
+ * Suffix ULL on constant 10 makes the expression
+ * CEC_TIM_START_BIT_TOTAL + 10ULL * len * CEC_TIM_DATA_BIT_TOTAL
+ * be evaluated using 64-bit unsigned arithmetic (u64), which
+ * is what ktime_sub_us expects as second argument.
+ */
+ ts = ktime_sub_us(ts, CEC_TIM_START_BIT_TOTAL +
+ 10ULL * len * CEC_TIM_DATA_BIT_TOTAL);
cec_queue_pin_cec_event(adap, false, ts);
ts = ktime_add_us(ts, CEC_TIM_START_BIT_LOW);
cec_queue_pin_cec_event(adap, true, ts);
--
2.7.4
\
 
 \ /
  Last update: 2018-02-05 22:00    [W:0.090 / U:7.840 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site