Re: [PATCH] staging: gpib: Remove a dead condition in if statement

From: Shuah Khan
Date: Tue Oct 15 2024 - 18:47:51 EST


On 10/15/24 14:06, Everest K.C. wrote:
The variable `residue` is an unsigned int, also the function
`fluke_get_dma_residue` returns an unsigned int. The value of
an unsigned int can only be 0 at minimum.
The less-than-zero comparision can never be true.
Fix it by removing the dead condition in the if statement.

This issue was reported by Coverity Scan.
Report:
CID 1600782: (#1 of 1): Macro compares unsigned to 0 (NO_EFFECT)
unsigned_compare: This less-than-zero comparison of an unsigned value
is never true. residue < 0U.

Fixes: 55936779f496 ("staging: gpib: Add Fluke cda based cards GPIB driver")
Signed-off-by: Everest K.C. <everestkc@xxxxxxxxxxxxxxxx>
---
drivers/staging/gpib/eastwood/fluke_gpib.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/staging/gpib/eastwood/fluke_gpib.c b/drivers/staging/gpib/eastwood/fluke_gpib.c
index f9f149db222d..51b4f9891a34 100644
--- a/drivers/staging/gpib/eastwood/fluke_gpib.c
+++ b/drivers/staging/gpib/eastwood/fluke_gpib.c
@@ -644,7 +644,7 @@ static int fluke_dma_read(gpib_board_t *board, uint8_t *buffer,
*/
usleep_range(10, 15);
residue = fluke_get_dma_residue(e_priv->dma_channel, dma_cookie);
- if (WARN_ON_ONCE(residue > length || residue < 0))
+ if (WARN_ON_ONCE(residue > length))

Are you sure this is the right fix? length is size_t
fluke_get_dma_residue() returns unsigned int - yes
the coverity report is correct, but should fluke_get_dma_residue()
return size_t?

return -EFAULT;
*bytes_read += length - residue;

bytes_read is also size_t

dmaengine_terminate_all(e_priv->dma_channel);

The patch should indicate it is against next. [PATCH next].

thanks,
-- Shuah