From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Bergmann Subject: Re: [v11, 7/8] base: soc: introduce soc_device_match() interface Date: Tue, 06 Sep 2016 14:46:08 +0200 Message-ID: <6515108.aCEls7dUuW@wuerfel> References: <1473150503-9550-1-git-send-email-yangbo.lu@nxp.com> <1473150503-9550-8-git-send-email-yangbo.lu@nxp.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Return-path: In-Reply-To: Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Ulf Hansson Cc: Yangbo Lu , linux-mmc , Scott Wood , "linuxppc-dev-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org" , "devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org" , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , linux-clk , "linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Mark Rutland , Rob Herring , Russell King , Jochen Friedrich , Joerg Roedel , Claudiu Manoil , Bhupesh List-Id: devicetree@vger.kernel.org On Tuesday, September 6, 2016 1:44:23 PM CEST Ulf Hansson wrote: > On 6 September 2016 at 10:28, Yangbo Lu wrote: > > We keep running into cases where device drivers want to know the exact > > version of the a SoC they are currently running on. In the past, this has > > usually been done through a vendor specific API that can be called by a > > driver, or by directly accessing some kind of version register that is > > not part of the device itself but that belongs to a global register area > > of the chip. Please add "From: Arnd Bergmann " as the first line, to preserve authorship. If you use "git send-email" or "git format-patch", that should happen automatically if the author field is set right (if not, use 'git commit --amend --author="Arnd Bergmann "' to fix it). > > + > > +/* > > + * soc_device_match - identify the SoC in the machine > > + * @matches: zero-terminated array of possible matches > > Perhaps also express the constraint on the matching entries. As you > need at least one of the ->machine(), ->family(), ->revision() or > ->soc_id() callbacks implemented, right!? They are not callbacks, just strings. Having an empty entry indicates the end of the array, and this is not called. > > + * > > + * returns the first matching entry of the argument array, or NULL > > + * if none of them match. > > + * > > + * This function is meant as a helper in place of of_match_node() > > + * in cases where either no device tree is available or the information > > + * in a device node is insufficient to identify a particular variant > > + * by its compatible strings or other properties. For new devices, > > + * the DT binding should always provide unique compatible strings > > + * that allow the use of of_match_node() instead. > > + * > > + * The calling function can use the .data entry of the > > + * soc_device_attribute to pass a structure or function pointer for > > + * each entry. > > I don't get the use case behind this, could you elaborate? > > Perhaps we should postpone adding the .data entry until we actually > see a need for it? I think the interface is rather useless without a way to figure out which entry you got. Almost all users of of_match_node() actually use the returned ->data field, and I expect this to be the same here. > > + */ > > +const struct soc_device_attribute *soc_device_match( > > + const struct soc_device_attribute *matches) > > +{ > > + struct device *dev; > > + int ret; > > + > > + for (ret = 0; ret == 0; matches++) { > > This loop looks a bit weird and unsafe. Ah, and I thought I was being clever ;-) > 1) Perhaps using a while loop makes this more readable? > 2) As this is an exported API, I guess validation of the ->matches > pointer needs to be done before accessing it. Sounds fine. > > + if (!(matches->machine || matches->family || > > + matches->revision || matches->soc_id)) > > + return NULL; > > + dev = NULL; > > There's no need to use a struct device just to assign it to NULL. > Instead just provide the function below with NULL. > > > + ret = bus_for_each_dev(&soc_bus_type, dev, (void *)matches, > > + soc_device_match_one); I don't remember what led to this, I think you are right, we should just pass NULL as most other callers. Thanks for the review. ARnd -- 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