From mboxrd@z Thu Jan  1 00:00:00 1970
From: =?iso-8859-1?Q?Ga=EBtan?= Rivet <gaetan.rivet@6wind.com>
Subject: Re: [PATCH v5 5/5] eal: simplify parameters of hotplug
	functions
Date: Thu, 4 Oct 2018 13:51:31 +0200
Message-ID: <20181004115131.do3mrikxujq7dx4o@bidouze.vm.6wind.com>
References: <20180907222727.20521-1-thomas@monjalon.net>
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To: Thomas Monjalon <thomas@monjalon.net>
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On Thu, Oct 04, 2018 at 01:46:54PM +0200, Thomas Monjalon wrote:
> 04/10/2018 11:44, Gaëtan Rivet:
> > On Thu, Oct 04, 2018 at 01:10:46AM +0200, Thomas Monjalon wrote:
> > > --- a/lib/librte_eal/common/eal_common_dev.c
> > > +++ b/lib/librte_eal/common/eal_common_dev.c
> > > @@ -129,46 +129,61 @@ int rte_eal_dev_detach(struct rte_device *dev)
> > >  
> > >  int
> > >  rte_eal_hotplug_add(const char *busname, const char *devname,
> > > -		    const char *devargs)
> > > +		    const char *drvargs)
> > >  {
> > > -	struct rte_bus *bus;
> > > -	struct rte_device *dev;
> > > -	struct rte_devargs *da;
> > >  	int ret;
> > > +	char *devargs = NULL;
> > > +	int size, length = -1;
> > >  
> > > -	bus = rte_bus_find_by_name(busname);
> > > -	if (bus == NULL) {
> > > -		RTE_LOG(ERR, EAL, "Cannot find bus (%s)\n", busname);
> > > -		return -ENOENT;
> > > -	}
> > > +	do { /* 2 iterations: first is to know string length */
> > > +		size = length + 1;
> > > +		length = snprintf(devargs, size, "%s:%s,%s", busname, devname, drvargs);
> > > +		if (length >= size)
> > > +			devargs = malloc(length + 1);
> > > +		if (devargs == NULL)
> > > +			return -ENOMEM;
> > > +	} while (size == 0);
> > 
> > I don't see a good reason for writing it this way.
> > You use an additional state (size) and complicate something that is
> > pretty straightforward. To make sure no error was written here, I had to
> > do step-by-step careful reading, this should not be required by clean
> > code.
> > 
> > You should remove this loop, which then allow removing size, and forces using
> > simple code-flow.
> 
> The only reason for this loop is to avoid duplicating the snprintf format
> in two calls.
> 
> It could be replaced by this:
> 
> 	length = snprintf(devargs, 0, "%s:%s,%s", busname, devname, drvargs);
> 	if (length < 0)
> 		return -EINVAL;
> 	devargs = malloc(length + 1);
> 	if (devargs == NULL)
> 		return -ENOMEM;
> 	snprintf(devargs, length + 1, "%s:%s,%s", busname, devname, drvargs);
> 
> Any preference?
> 
> 

Yes, the second is cleaner IMO.

-- 
Gaëtan Rivet
6WIND