> -----Original Message----- > From: Marc Zyngier [mailto:marc.zyngier@xxxxxxx] > Sent: Wednesday, February 3, 2016 10:57 AM > To: Bjorn Helgaas <helgaas@xxxxxxxxxx>; Jake Oshins > <jakeo@xxxxxxxxxxxxx> > Cc: gregkh@xxxxxxxxxxxxxxxxxxx; KY Srinivasan <kys@xxxxxxxxxxxxx>; linux- > kernel@xxxxxxxxxxxxxxx; devel@xxxxxxxxxxxxxxxxxxxxxx; Haiyang Zhang > <haiyangz@xxxxxxxxxxxxx>; bhelgaas@xxxxxxxxxx; linux- > pci@xxxxxxxxxxxxxxx > Subject: Re: [PATCH RESEND 1/3] PCI: Add fwnode_handle to pci_sysdata > > On 03/02/16 18:51, Bjorn Helgaas wrote: > > On Wed, Feb 03, 2016 at 06:32:20PM +0000, Jake Oshins wrote: > >>> -----Original Message----- > >>> From: Bjorn Helgaas [mailto:helgaas@xxxxxxxxxx] > >>> Sent: Wednesday, February 3, 2016 10:25 AM > >>> To: Jake Oshins <jakeo@xxxxxxxxxxxxx> [snip] > >>>> > >>>> +#ifndef pci_root_bus_fwnode > >>>> +#define pci_root_bus_fwnode(bus) ((void)(bus), NULL) > >>> > >>> Huh, interesting. This is new for me; I guess the idea is that we at least > >>> evaluate "bus" even when pci_root_bus_fwnode isn't defined, so the > >>> compiler can catch egregious errors? > >>> > >> > >> This was a suggestion by Mark Zyngier. It made the non-x86 architectures > build benignly. If you'd like it done differently, I'm open to suggestion. > > I don't remember suggesting the use of the comma operator, but just to > check that pci_root_bus_fwnode wasn't previously defined. > > > Something like "#define pci_root_bus_fwnode(bus) NULL" would be > > typical. What I'm curious about is the use of the comma operator. > > I'm not opposed to it; I'm just trying to understand why it makes a > > difference. > > I guess it flags the variable as used, and prevents an overly sensitive > compiler from being loud and obnoxious... Just a guess though. > > M. > -- I was just copying the form that was in the code that Marc pointed out, somewhere else. I have no particular attachment to this construct. Honestly, since I'm still relatively new to the Linux codebase, I just assumed that was a common form that I should follow suit on. If you tell me that the simpler NULL is more typical, I prefer that. I'll simplify this when I resend the patch series. Thanks, Jake _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
