device: Introduce pcidev_on_root() and friends

Semantics of dev_find_slot() are ill in the sense that
it only works after device enumeration has completed in
ramstage. Plan is to declare it as deprecated.

Introduce pcidev_on_root() and pcidev_path_on_root()
functions to replace cases where this was called with
static argument bus == 0. New implementation only walks
the root bus of the PCI tree, while old one walked
the entire linked list of devices.

Introduce pcidev_path_behind() to replace cases where
argument bus != 0. The required parent node is typically
one of the PCIe root functions that you locate using
pcidev_on_root() above.

New forms are safe to use with early devicetree and
before PCI bus numbers have been assigned.

Change-Id: Ie20598d48b4cf6e35e45fc90804bad4728437fc6
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/26447
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Werner Zeh <werner.zeh@siemens.com>

src/device/device_const.c

@@ -22,6 +22,7 @@
 #include <device/device.h>
 #include <device/path.h>
 #include <device/pci.h>
+#include <device/pci_def.h>
 #include <device/resource.h>
 
 /** Linked list of ALL devices */
@@ -172,6 +173,31 @@ DEVTREE_CONST struct device *find_dev_path(
 	return child;
 }
 
+DEVTREE_CONST struct device *pcidev_path_behind(
+	const struct bus *parent, pci_devfn_t devfn)
+{
+	const struct device_path path = {
+		.type = DEVICE_PATH_PCI,
+		.pci.devfn = devfn,
+	};
+	return find_dev_path(parent, &path);
+}
+
+DEVTREE_CONST struct device *pcidev_path_on_root(pci_devfn_t devfn)
+{
+	DEVTREE_CONST struct device *pci_domain;
+
+	pci_domain = dev_find_path(NULL, DEVICE_PATH_DOMAIN);
+	if (!pci_domain)
+		return NULL;
+	return pcidev_path_behind(pci_domain->link_list, devfn);
+}
+
+DEVTREE_CONST struct device *pcidev_on_root(uint8_t dev, uint8_t fn)
+{
+	return pcidev_path_on_root(PCI_DEVFN(dev, fn));
+}
+
 /**
  * Given an SMBus bus and a device number, find the device structure.
  *

src/include/device/device.h

@@ -276,6 +276,11 @@ DEVTREE_CONST struct device *dev_find_slot_pnp(u16 port, u16 device);
 DEVTREE_CONST struct device *dev_bus_each_child(const struct bus *parent,
 				DEVTREE_CONST struct device *prev_child);
 
+DEVTREE_CONST struct device *pcidev_path_behind(const struct bus *parent,
+		pci_devfn_t devfn);
+DEVTREE_CONST struct device *pcidev_path_on_root(pci_devfn_t devfn);
+DEVTREE_CONST struct device *pcidev_on_root(uint8_t dev, uint8_t fn);
+
 void scan_smbus(struct device *bus);
 void scan_generic_bus(struct device *bus);
 void scan_static_bus(struct device *bus);