On Thu, 6 Dec 2012 08:06:20 +0530, Viresh Kumar <viresh.ku...@linaro.org> wrote: > On 6 December 2012 04:12, Grant Likely <grant.lik...@secretlab.ca> wrote: > > On Sat, 1 Dec 2012 00:33:46 +0530, Viresh Kumar <viresh.ku...@linaro.org> > > wrote: > >> This first tries to match the table my patch added, _BUT_ the string will > >> never match as we had "st,stmpe810" in table and "stmpe810" in dev. > > > > of_driver_match_device() matches against the compatible list in > > dev->of_node, not against the device name. So, if the compatible > > property has a string that is in the table, then it really should match > > against it. > > Grant, but isn't it true that the final device's name would not be the DT > way of names? It would simply be "stmpe810" for us and so if we have > multiple instances of stmpe on a board, we need to distinguish them > ourselves? One way for that was passing id for these instances, which > would finally be used, when we create platform devices for sub-modules > of stmpe (gpio, keypad, ts, etc).
of_modalias_node() is based on a *heruistic*. It is a best-effort attempt to convert the node's compatible lists into a string that will match against an existing driver. In the simple case it works because historically i2c has used the chip name for the driver name. We get lucky and a lot of drivers will work with DT without changes. However, it is in no way guaranteed. Sometimes the strings won't line up or a certain silicon vendor will have an extra errata or feature. In that case it makes sense to use a DT match table that can parse the entries in the compatible list. Or a driver can call of_ helper functions. For example, it might call of_alias_get_id() to figure out which device id it needs. That's why the full DT parsing exists. It's the fallback when the simple heuristic fails. Only use it when you need to. g. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
