[Skiboot] [PATCH 1/3] core/pci: Add for_each_pci_dev()
Oliver O'Halloran
oohall at gmail.com
Tue Aug 22 18:15:41 AEST 2017
Add an interation helper for PCI devices. This is functionally identical
to the pci_walk_devs() helper function, but it allows us to write linear
code rather than dropping us into the middle of callback hell.
Signed-off-by: Oliver O'Halloran <oohall at gmail.com>
---
core/pci.c | 84 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
include/pci.h | 9 +++++++
2 files changed, 93 insertions(+)
diff --git a/core/pci.c b/core/pci.c
index 4296180ad111..c5d2fba36508 100644
--- a/core/pci.c
+++ b/core/pci.c
@@ -1798,6 +1798,90 @@ static struct pci_device *__pci_walk_dev(struct phb *phb,
return NULL;
}
+/*
+ * pci_next_dev(phb, prev, pass) - Iteration worker function
+ *
+ * phb - phb that we're iterating
+ * prev - the last pci_device returned by pci_next_dev
+ *
+ * pass - a cookie used to track the iteration state. See below if you
+ * really want to know the details.
+ */
+struct pci_device *pci_next_dev(struct phb *phb, struct pci_device *prev,
+ int *pass)
+{
+ struct pci_device *next, *last;
+ struct list_head *siblings;
+
+ assert(phb);
+
+ /* start of iteration */
+ if (!prev) {
+ *pass = 0;
+ return list_top(&phb->devices, struct pci_device, link);
+ }
+
+up:
+ assert(prev);
+
+ if (prev->parent)
+ siblings = &prev->parent->children;
+ else
+ siblings = &phb->devices;
+
+ last = list_tail(siblings, struct pci_device, link);
+ assert(last);
+
+ /*
+ * You made it this far so you get an explaination!
+ *
+ * We need to ensure that the iteration order is correct, that is we are
+ * supposed to look at each *device* on a bus before looking at the
+ * *child buses* below those devices, as is done in pci_walk_devs(). In
+ * other words, we do two pases of every bus.
+ *
+ * The 'pass' variable is used to track which pass we are on. When it's
+ * even we are just visiting each device and when odd we are descending
+ * into child buses if we find any.
+ */
+ if (prev == last) {
+ if (*pass & 1) { /* end of the odd pass */
+ if (!prev->parent) {
+ assert(*pass == 1);
+ return NULL;
+ }
+
+ /* back to the odd pass across the parent's bus */
+ (*pass) -= 2;
+ prev = prev->parent;
+ goto up;
+ } else {
+ next = list_top(siblings, struct pci_device, link);
+ (*pass)++;
+ }
+ } else {
+ next = list_entry(prev->link.next, struct pci_device, link);
+ }
+
+ /* now find the device we should return */
+ if (!(*pass & 1))
+ return next;
+
+ /* for an odd pass we scan for another child bus to descend into */
+ while (list_empty(&next->children)) {
+ if (next == last) {
+ prev = last;
+ goto up;
+ }
+
+ next = list_entry(next->link.next, struct pci_device, link);
+ }
+
+ /* increment pass so it's even */
+ (*pass)++;
+ return list_top(&next->children, struct pci_device, link);
+}
+
struct pci_device *pci_walk_dev(struct phb *phb,
struct pci_device *pd,
int (*cb)(struct phb *,
diff --git a/include/pci.h b/include/pci.h
index 54a62fd19a99..81ad62f8fa19 100644
--- a/include/pci.h
+++ b/include/pci.h
@@ -460,6 +460,15 @@ static inline struct phb *__pci_next_phb_idx(uint64_t *phb_id) {
for (uint64_t __phb_idx = 0; \
(phb = __pci_next_phb_idx(&__phb_idx)) ; )
+
+struct pci_device *pci_next_dev(struct phb *phb, struct pci_device *pd,
+ int *pass);
+
+/* pass should be an int *, see pci_next_dev() for details */
+#define for_each_pci_dev(phb, pd, pass) \
+ for (pd = pci_next_dev(phb, NULL, pass); pd; \
+ pd = pci_next_dev(phb, pd, pass))
+
/* Device tree */
extern void pci_std_swizzle_irq_map(struct dt_node *dt_node,
struct pci_device *pd,
--
2.9.5
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