[RFC PATCH v3 2/2] dt: add custom device creation to platform bus scan
From: arnd@arndb.de (Arnd Bergmann)
Date: 2011-05-27 12:06:18
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linux-devicetree
On Thursday 26 May 2011, Rob Herring wrote:
On 05/26/2011 08:11 AM, Arnd Bergmann wrote:quoted
On Wednesday 25 May 2011, Rob Herring wrote: This creates a confusing mix of match table entries: Normally, all entries in the match table are meant to identify child buses, but if I read your patch correctly, you now also need to match on the amba devices themselves, including the creation of platform devices for each child device node under an amba device.We should only create devices for each matching bus and the immediate children of each bus. A child device of an amba device would be something like an i2c bus which we don't want to create devices for. Or am I missing something?
Exactly, that was my point.
quoted
I don't think that was the intention. Maybe we need to pass two match tables into of_platform_bus_probe() instead: one to identify the buses, and another one that is used to create the actual devices.That was my original thinking too, but some reason I had concluded 1 could get by with just 1 table. After more thought, I think you are right. In fact, I broke platform device creation with this patch. I need to be able to tell if no match means create a platform device (child of bus) or not (child of a device).
Ok.
quoted hunk
@@ -234,18 +237,32 @@ static int of_platform_bus_create(structdevice_node *bus, return 0; } - dev = of_platform_device_create(bus, NULL, parent); - if (!dev || !of_match_node(matches, bus)) - return 0; - - for_each_child_of_node(bus, child) { - pr_debug(" create child: %s\n", child->full_name); - rc = of_platform_bus_create(child, matches, &dev->dev, strict); - if (rc) { - of_node_put(child); - break; + id = of_match_node(bus_matches, bus); + if (id) { + dev = of_platform_device_create(bus, NULL, parent); + if (!dev) + return 0; + for_each_child_of_node(bus, child) { + pr_debug(" create child: %s\n", child->full_name); + rc = of_platform_bus_create(child, bus_matches, + dev_matches, dev, strict); + if (rc) { + of_node_put(child); + break; + } } + return rc; } + + id = of_match_node(dev_matches, bus); + mdata = id ? id->data : NULL; + if (id && mdata && mdata->dev_create) + dev = mdata->dev_create(bus, parent); + else + dev = of_platform_device_create(bus, NULL, parent); + if (!dev) + return 0; +
Yes, that looks like it should work. It still feels a bit strange, because it's not exactly how we normally probe devices: In all other cases, we bind a device to a driver when we find it, and that driver in turn scans it, and potentially creates child devices that it finds. What we do here is to let the platform decide how to interpret the data that is coming in. To make the probing more well-behaved, another approach would be: * Bind a platform_driver to compatible="arm,amba" (or whatever we had in the binding). * In that driver, do nothing except register an amba_device as a child. This would create a somewhat deeper device hierarchy, but be still completely logical: you have a device that cannot be probed (identified simply by its register space), which can be probed internally because the registers actually have a meaning. Arnd