原文网址：http://www.cnblogs.com/biglucky/p/4057499.html
devicetree中数据和structdevice有什么关系
总体来说，devicetree与structdevice的关系应该还是在其生成platformdevice的时候，一直传递的structdevice *parent参数。下面先把其源码中传递过程描述如下（仍以At91rm9200为例）：
1,
DT_MACHINE_START(at91sam_dt,"Atmel AT91SAM (Device Tree)")
/*Maintainer: Atmel */
.timer =&at91sam926x_timer,
.map_io =at91_map_io,
.init_early =at91_dt_initialize,
.init_irq =at91_dt_init_irq,
.init_machine =at91_dt_device_init,
.dt_compat =at91_dt_board_compat,
MACHINE_END
2,
staticvoid __init at91_dt_device_init(void)
{
of_platform_populate(NULL,of_default_bus_match_table, NULL, NULL);
}
3,
/**
*of_platform_populate() - Populate platform_devices from device treedata
*@root: parent of the first level to probe or NULL for the root of thetree
*@matches: match table, NULL to use the default
*@parent: parent to hook devicesfrom, NULL for toplevel
*
*Similar to of_platform_bus_probe(), this function walks the devicetree
*and creates devices from nodes. It differs in that it follows themodern
*convention of requiring all device nodes to have a ‘compatible‘property,
*and it is suitable for creating devices which are children of theroot
*node (of_platform_bus_probe will only create children of the rootwhich
*are selected by the @matches argument).
*
*New board support should be using this function instead of
*of_platform_bus_probe().
*
*Returns 0 on success, < 0 on failure.
*/
//从devicetree数据中populateplatform devices。
intof_platform_populate(structdevice_node *root,
conststruct of_device_id *matches,
conststruct of_dev_auxdata *lookup,
structdevice *parent)
{
structdevice_node *child;
intrc = 0;
root= root ? of_node_get(root) : of_find_node_by_path("/");
if(!root)
return-EINVAL;
for_each_child_of_node(root,child) {
//生成platformdevice
rc= of_platform_bus_create(child,matches, lookup, parent,true);
if(rc)
break;
}
of_node_put(root);
returnrc;
}
4,
/**
*of_platform_bus_create() - Create a device for a node and itschildren.
*@bus: device node of the bus to instantiate
*@matches: match table for bus nodes
*@lookup: auxdata table for matching id and platform_data with devicenodes
*@parent: parent for new device, or NULL for top level.
*@strict: require compatible property
*
*Creates a platform_device for the provided device_node, andoptionally
*recursively create devices for all the child nodes.
*/
//为节点和其孩子节点生成一个设备文件。
staticint of_platform_bus_create(structdevice_node *bus,
const struct of_device_id *matches,
const struct of_dev_auxdata *lookup,
struct device *parent, boolstrict)
{
conststruct of_dev_auxdata *auxdata;
structdevice_node *child;
structplatform_device *dev;
constchar *bus_id = NULL;
void*platform_data = NULL;
intrc = 0;
/*Make sure it has a compatible property */
if(strict && (!of_get_property(bus, "compatible",NULL))) {
pr_debug("%s()- skipping %s, no compatible prop\n",
__func__, bus->full_name);
return0;
}
auxdata= of_dev_lookup(lookup, bus);
if(auxdata) {
bus_id= auxdata->name;
platform_data= auxdata->platform_data;
}
if(of_device_is_compatible(bus, "arm,primecell")) {
of_amba_device_create(bus,bus_id, platform_data, parent);
return0;
}
dev= of_platform_device_create_pdata(bus,bus_id, platform_data, parent);
if(!dev || !of_match_node(matches, bus))
return0;
for_each_child_of_node(bus,child) {
pr_debug(" create child: %s\n", child->full_name);
rc= of_platform_bus_create(child, matches, lookup, &dev->dev,strict);
if(rc) {
of_node_put(child);
break;
}
}
returnrc;
}
代码在这儿分了两步走：4.1和4.2。
4.1
staticstruct amba_device *of_amba_device_create(structdevice_node *node,
const char *bus_id,
void *platform_data,
struct device *parent)
{
structamba_device *dev;
constvoid *prop;
inti, ret;
pr_debug("Creatingamba device %s\n", node->full_name);
if(!of_device_is_available(node))
returnNULL;
dev= amba_device_alloc(NULL, 0, 0);
if(!dev)
returnNULL;
/*setup generic device info */
dev->dev.coherent_dma_mask= ~0;
dev->dev.of_node= of_node_get(node);
dev->dev.parent= parent;
dev->dev.platform_data= platform_data;
…...
}
4.2
/**
*of_platform_device_create_pdata - Alloc, initialize and register anof_device
*@np: pointer to node to create device for
*@bus_id: name to assign device
*@platform_data: pointer to populate platform_data pointer with
*@parent: Linux device model parentdevice.
*
*Returns pointer to created platform device, or NULL if a device wasnot
*registered. Unavailable devices will not get registered.
*/
//分配内存，初始化和注册一个of_device
structplatform_device *of_platform_device_create_pdata(
structdevice_node *np,
constchar *bus_id,
void*platform_data,
structdevice *parent)
{
structplatform_device *dev;
if(!of_device_is_available(np))
returnNULL;
dev= of_device_alloc(np,bus_id, parent);
…...
returndev;
}
4.2.1
/**
*of_device_alloc - Allocate and initialize an of_device
*@np: device node to assign to device
*@bus_id: Name to assign to the device. May be null to use defaultname.
*@parent: Parent device.
*/
//分配内存和初始化of_device
structplatform_device *of_device_alloc(structdevice_node *np,
const char *bus_id,
struct device *parent)
{
structplatform_device *dev;
intrc, i, num_reg = 0, num_irq;
structresource *res, temp_res;
dev= platform_device_alloc("", -1);
if(!dev)
returnNULL;
/*count the io and irq resources */
if(of_can_translate_address(np))
while(of_address_to_resource(np, num_reg, &temp_res) == 0)
num_reg++;
num_irq= of_irq_count(np);
/*Populate the resource table */
if(num_irq || num_reg) {
res= kzalloc(sizeof(*res) * (num_irq + num_reg), GFP_KERNEL);
if(!res) {
platform_device_put(dev);
returnNULL;
}
dev->num_resources= num_reg + num_irq;
dev->resource= res;
for(i = 0; i < num_reg; i++, res++) {
rc= of_address_to_resource(np, i, res);
WARN_ON(rc);
}
WARN_ON(of_irq_to_resource_table(np,res, num_irq) != num_irq);
}
dev->dev.of_node= of_node_get(np);
#ifdefined(CONFIG_MICROBLAZE)
dev->dev.dma_mask= &dev->archdata.dma_mask;
#endif
dev->dev.parent= parent;
if(bus_id)
dev_set_name(&dev->dev,"%s", bus_id);
else
of_device_make_bus_id(&dev->dev);
returndev;
}
总的分析：parent参数开始初始化为NULL，其中一直没有赋值，直到最后赋值给platformdevice的dev.parent属性。其中关系耐人寻味。