Hi Grant, Thanks for the explanation.
On Sat, Mar 12, 2011 at 02:46:20AM -0700, Grant Likely wrote: > On Sat, Mar 12, 2011 at 03:00:57PM +0800, Shawn Guo wrote: > > Hello all, > > > > I'm looking at function of_device_alloc in drivers/of/platform.c, and > > surprisingly found that the platform device instance id is being > > hard-coded as -1 when calling platform_device_alloc. Does this mean > > that there is no support of pdev id in DT? > > Correct, when generating devices from the DT, the core code has no way > of knowing what the 'preferred' number of the device should be. It If we have this number in DT, the core code gets the way. > expects that when the driver's .probe() hook is called, the driver is > smart enough to enumerate the automatically. > Considering that many drivers on ARM platform are replying on pdev->id, we will have to make every single of such drivers become smart. > > If yes, can anyone please > > help me understand why we do not have something in DT node to reflect > > this id and get it supported? Or this is something on TODO list? > > Ideally, you shouldn't be relying on .id at all. Fix your device > drivers to enumerate correctly, and use explicit phandle references > when specifying connections between devices. > Again, many existing ARM drivers will need to get fixed. > That said, I do understand the issue with needing to reference a > specific device by name; like for specifying the console device. In > those cases, the correct way to figure out what number a device is > supposed to have is to add a property to the /aliases node (see ePAPR To me, specifying the id in DT, and letting core code get it from DT and pass it to platform_device_alloc seems more natural and straight-forward than creating /aliases node and then parsing it in every single driver that need to figure out the device number. The most important thing is that the ARM drivers relying on pdev->id will need no changes on this point, if we have pdev->id supported in DT core code. I can live with the approach you tell, but I doubt that ARM community people will have the same question, when we post the driver changes for DT support. > for a description of /aliases). However, even in this case the driver > should be looking at the device tree data, and not depend on the value > in pdev->id. > If we have pdev->id specified in DT and retrieved it by core code, the driver is actually looking at the data from DT. -- Regards, Shawn _______________________________________________ linaro-dev mailing list linaro-dev@lists.linaro.org http://lists.linaro.org/mailman/listinfo/linaro-dev
