From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joerg Roedel Subject: Re: [PATCH 1/2] of: base: Allow more args than MAX_PHANDLE_ARGS if required Date: Thu, 16 Jul 2015 13:09:00 +0200 Message-ID: <20150716110900.GA30130@suse.de> References: <1437035444-13867-1-git-send-email-joro@8bytes.org> <1437035444-13867-2-git-send-email-joro@8bytes.org> <20150716102325.GC26390@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20150716102325.GC26390-5wv7dgnIgG8@public.gmane.org> Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Will Deacon Cc: Joerg Roedel , "grant.likely-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org" , Rob Herring , "linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org" , "iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org" , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" List-Id: devicetree@vger.kernel.org Hi Will, On Thu, Jul 16, 2015 at 11:23:26AM +0100, Will Deacon wrote: > On Thu, Jul 16, 2015 at 09:30:43AM +0100, Joerg Roedel wrote: > > +struct of_phandle_args *of_alloc_phandle_args(int size) > > +{ > > + struct of_phandle_args *args; > > + int e = max(0, size - MAX_PHANDLE_ARGS); > > + > > + args = kzalloc(sizeof(struct of_phandle_args) + e * sizeof(uint32_t), > > + GFP_KERNEL); > > Should you also update args->args_count to reflect the extended array? The args_count member just tells us how many of the array elements are used and not how many there are. So it doesn't need to be updated here. > That said, extending the fixed-size array member like this feels a bit > fragile. Does GCC not complain about out-of-bounds accesses if you > statically address args->args[MAX_PHANDLE_ARGS]? Admittedly, I can't > think *why* this would be break (things like additional padding will be > harmless), but I'm not intimate with the C standard. Yeah, I agree, it is not the best possible solution. But this way I don't need to update all callers, and thus it works better with our development model. But I am open for suggestions on how to solve this problem better. In fact, my main motivation in sending this was to get the discussion about an upstreamable solution started :) Lets see what the device-tree maintainers have to say. > I guess the more worrying possibility is if somebody adds a new member to > the end of of_phandle_args. I should probably add a comment there. Joerg -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html