From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sakari Ailus Subject: Re: [PATCH 5/5] lib/vsprintf: Add %pfw conversion specifier for printing fwnode names Date: Tue, 26 Mar 2019 15:39:47 +0200 Message-ID: <20190326133947.pbniwkvszlahw3dr@paasikivi.fi.intel.com> References: <20190322152930.16642-1-sakari.ailus@linux.intel.com> <20190322152930.16642-6-sakari.ailus@linux.intel.com> <20190322172114.GY9224@smile.fi.intel.com> <20190324181745.vgckevapfwi7mul7@mara.localdomain> <20190326131353.GY9224@smile.fi.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20190326131353.GY9224@smile.fi.intel.com> Sender: linux-kernel-owner@vger.kernel.org To: Andy Shevchenko Cc: Petr Mladek , linux-kernel@vger.kernel.org, rafael@kernel.org, linux-acpi@vger.kernel.org, devicetree@vger.kernel.org, Heikki Krogerus List-Id: linux-acpi@vger.kernel.org Hi Andy, On Tue, Mar 26, 2019 at 03:13:53PM +0200, Andy Shevchenko wrote: > On Sun, Mar 24, 2019 at 08:17:46PM +0200, Sakari Ailus wrote: > > On Fri, Mar 22, 2019 at 07:21:14PM +0200, Andy Shevchenko wrote: > > > On Fri, Mar 22, 2019 at 05:29:30PM +0200, Sakari Ailus wrote: > > > > Add support for %pfw conversion specifier (with "f" and "P" modifiers) to > > > > support printing full path of the node, including its name ("f") and only > > > > the node's name ("P") in the printk family of functions. The two flags > > > > have equivalent functionality to existing %pOF with the same two modifiers > > > > ("f" and "P") on OF based systems. The ability to do the same on ACPI > > > > based systems is added by this patch. > > > > > > Do we encourage people to use it instead of %pOF cases where it is suitable? > > > > For code that is used on both OF and ACPI based systems, I think so. But if > > you have something that is only used on OF, %pOF is better --- it has more > > functionality that seems quite OF specific. In general I think the ability > > to print a node's full name is way more important on OF. On ACPI you don't > > need it so often --- which is probably the reason it hasn't been supported. > > But if code is going to support ACPI and DT and at the same time use %pOF > extensions that are not covered by %pfw it would be inconsistent somehow. What you mostly need are the full name and the name of a given node. I wasn't sure whether adding more would have been relevant, and at least it is likely to have few if any users, so I didn't add that yet. Do not that it can be implemented later on if it's needed --- that's also why the modifiers are aligned with %pOF. > > > > > On ACPI based systems the resulting strings look like > > > > > > > > \_SB.PCI0.CIO2.port@1.endpoint@0 > > > > > > > > where the nodes are separated by a dot (".") and the first three are > > > > ACPI device nodes and the latter two ACPI data nodes. > > > > > > Do we support swnode here? > > > > Good question. The swnodes have no hierarchy at the moment (they're only > > created for a struct device as a parent) and they do not have human-readable > > names. So I'd say it's not relevant right now. Should these two change, > > support for swnode could (and should) be added later on. > > Heikki, what do you think about this? > > > > > + if ((unsigned long)fwnode < PAGE_SIZE) > > > > + return string(buf, end, "(null)", spec); > > > > > > Just put there a NULL pointer, we would not like to maintain duplicated strings > > > over the kernel. > > > > > > I remember Petr has a patch series related to address space check, though I > > > don't remember the status of affairs. > > > > This bit has been actually adopted from the OF counterpart. If there are > > improvements in this area, then I'd just change both at the same time. > > The patch series by Petr I mentioned takes care about OF case. But it doesn't > have covered yours by obvious reasons. Do you happen to have a pointer to it? > > > > > + for (pass = false; strspn(fmt, modifiers); fmt++, pass = true) { > > > > > > I don't see test cases. > > > > > > What would we get out of %pfwfffPPPfff? > > > > > > Hint: I'm expecting above to be equivalent to %pfwf > > > > I guess it's a matter of expectations. :-) > > Common sense and basic expectations from all of %p extensions. > > > Again this works the same way > > than the OF counterpart. > > OF lacks of testing apparently. > > > Right now there's little to print (just the name > > and the full name), but if support is added for more, then this mechanism is > > fully relevant again. > > > > The alternative would be to remove that now and add it back if it's needed > > again. I have a slight preference towards keeping it extensible (i.e. as > > it's now). > > See how other helpers do parse this. The behaviour on others is different indeed, you're generally printing a single item at a time. The question rather is, whether we want to be compatible with %pOF going forward or not. I'd prefer that, so using the fwnode API would be easier. -- Regards, Sakari Ailus sakari.ailus@linux.intel.com