Re: [dpdk-dev] [PATCH v2] eal/linuxapp: fix return value check of mknod()

[Ferruh Yigit <ferruh.yigit@intel.com>]

Hi Wenzhuo,

On 11/16/2016 3:28 AM, Lu, Wenzhuo wrote:
> Hi Wei,
> 
>> -----Original Message-----
>> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Wei Dai
>> Sent: Wednesday, November 16, 2016 10:41 AM
>> To: dev@dpdk.org; Burakov, Anatoly; david.marchand@6wind.com; Dai, Wei
>> Subject: [dpdk-dev] [PATCH v2] eal/linuxapp: fix return value check of mknod()
>>
>> In function pci_mknod_uio_dev() in lib/librte_eal/eal/eal_pci_uio.c, The return
>> value of mknod() is ret, not f got by fopen().
>> So the value of ret should be checked for mknod().
>>
>> Fixes: 67c536bdad93 ("pci: move uio mapping in a dedicated file")
>>
>> Signed-off-by: Wei Dai <wei.dai@intel.com>
>> ---
>> fix my local git setting and send same patch again to make merging easier
>>
>>  lib/librte_eal/linuxapp/eal/eal_pci_uio.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/lib/librte_eal/linuxapp/eal/eal_pci_uio.c
>> b/lib/librte_eal/linuxapp/eal/eal_pci_uio.c
>> index 1786b75..3e4ffb5 100644
>> --- a/lib/librte_eal/linuxapp/eal/eal_pci_uio.c
>> +++ b/lib/librte_eal/linuxapp/eal/eal_pci_uio.c
>> @@ -133,7 +133,7 @@ pci_mknod_uio_dev(const char *sysfs_uio_path,
>> unsigned uio_num)
>>  	snprintf(filename, sizeof(filename), "/dev/uio%u", uio_num);
>>  	dev = makedev(major, minor);
>>  	ret = mknod(filename, S_IFCHR | S_IRUSR | S_IWUSR, dev);
>> -	if (f == NULL) {
>> +	if (ret != 0) {
> I think checkpatch will suggest to just use if (ret)

Your are right, default checkpatch.pl complains about this usage (with
--strict option), but:

- According DPDK coding style this usage is preferred (although I
personally prefer kernel one..)

http://dpdk.org/doc/guides/contributing/coding_style.html#null-pointers

"
if (p == NULL) /* Good, compare pointer to NULL */

if (!p) /* Bad, using ! on pointer */
"

- This warning disabled in dpdk scripts/checkpatches.sh by "--ignore
COMPARISON_TO_NULL", so it shouldn't complain.