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

["Dai, Wei" <wei.dai@intel.com>]

Thanks to Yigit Ferruh and Wenzhuo for your guide.
Several months ago, I download checkpatch.pl and put it in /root/bin/.
In /root/.bash_profile in my server,  there is line :export DPDK_CHECKPATCH_PATH=/root/bin/checkpatch.pl
Before I send this patch, I have run checkpath.sh to check it and it show no error.
./scripts/checkpatch.sh -v v2-0001-eal-*.patch

By search ' != 0', there are many lines in many modules of DPDK.
So I think ' !=0' is OK.

> -----Original Message-----
> From: Yigit, Ferruh
> Sent: Wednesday, November 16, 2016 7:04 PM
> To: Lu, Wenzhuo <wenzhuo.lu@intel.com>; Dai, Wei <wei.dai@intel.com>;
> dev@dpdk.org; Burakov, Anatoly <anatoly.burakov@intel.com>;
> david.marchand@6wind.com
> Subject: Re: [dpdk-dev] [PATCH v2] eal/linuxapp: fix return value check of
> mknod()
> 
> 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.
> 
>