Re: [PATCH v2 1/2] PCI: Add pci_find_next_dvsec_capability to find next Designated VSEC

[Bjorn Helgaas]

Don't re-post just for this, but if you do repost, add "()" after the
function name in the subject line, as you did for the 2/2 patch.

On Tue, Aug 08, 2023 at 12:08:57PM +0800, Xiongfeng Wang wrote:
> Some devices may have several DVSEC (Designated Vendor-Specific Extended
> Capability) entries with the same DVSEC ID. Add
> pci_find_next_dvsec_capability() to find them all.

[PATCH v2 1/2] PCI: Add pci_find_next_dvsec_capability to find next Designated VSEC

[Xiongfeng Wang]

Some devices may have several DVSEC (Designated Vendor-Specific Extended
Capability) entries with the same DVSEC ID. Add
pci_find_next_dvsec_capability() to find them all.

Signed-off-by: Xiongfeng Wang 
Reviewed-by: Andrew Donnellan 
Acked-by: Bjorn Helgaas 
---
 drivers/pci/pci.c   | 39 ++-
 include/linux/pci.h |  2 ++
 2 files changed, 28 insertions(+), 13 deletions(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 60230da957e0..2ff5b1ce0eec 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -749,35 +749,48 @@ u16 pci_find_vsec_capability(struct pci_dev *dev, u16 
vendor, int cap)
 EXPORT_SYMBOL_GPL(pci_find_vsec_capability);
 
 /**
- * pci_find_dvsec_capability - Find DVSEC for vendor
+ * pci_find_next_dvsec_capability - Find next DVSEC for vendor
  * @dev: PCI device to query
+ * @start: Address at which to start looking (0 to start at beginning of list)
  * @vendor: Vendor ID to match for the DVSEC
- * @dvsec: Designated Vendor-specific capability ID
+ * @dvsec: Vendor-defined DVSEC ID
  *
- * If DVSEC has Vendor ID @vendor and DVSEC ID @dvsec return the capability
- * offset in config space; otherwise return 0.
+ * Returns the address of the next DVSEC if the DVSEC has Vendor ID @vendor and
+ * DVSEC ID @dvsec; otherwise return 0. DVSEC can occur several times with the
+ * same DVSEC ID for some devices, and this provides a way to find them all.
  */
-u16 pci_find_dvsec_capability(struct pci_dev *dev, u16 vendor, u16 dvsec)
+u16 pci_find_next_dvsec_capability(struct pci_dev *dev, u16 start, u16 vendor,
+  u16 dvsec)
 {
-   int pos;
+   u16 pos = start;
 
-   pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_DVSEC);
-   if (!pos)
-   return 0;
-
-   while (pos) {
+   while ((pos = pci_find_next_ext_capability(dev, pos,
+ PCI_EXT_CAP_ID_DVSEC))) {
u16 v, id;
 
pci_read_config_word(dev, pos + PCI_DVSEC_HEADER1, );
pci_read_config_word(dev, pos + PCI_DVSEC_HEADER2, );
if (vendor == v && dvsec == id)
return pos;
-
-   pos = pci_find_next_ext_capability(dev, pos, 
PCI_EXT_CAP_ID_DVSEC);
}
 
return 0;
 }
+EXPORT_SYMBOL_GPL(pci_find_next_dvsec_capability);
+
+/**
+ * pci_find_dvsec_capability - Find DVSEC for vendor
+ * @dev: PCI device to query
+ * @vendor: Vendor ID to match for the DVSEC
+ * @dvsec: Vendor-defined DVSEC ID
+ *
+ * If DVSEC has Vendor ID @vendor and DVSEC ID @dvsec return the capability
+ * offset in config space; otherwise return 0.
+ */
+u16 pci_find_dvsec_capability(struct pci_dev *dev, u16 vendor, u16 dvsec)
+{
+   return pci_find_next_dvsec_capability(dev, 0, vendor, dvsec);
+}
 EXPORT_SYMBOL_GPL(pci_find_dvsec_capability);
 
 /**
diff --git a/include/linux/pci.h b/include/linux/pci.h
index c69a2cc1f412..82bb905daf72 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1168,6 +1168,8 @@ u16 pci_find_next_ext_capability(struct pci_dev *dev, u16 
pos, int cap);
 struct pci_bus *pci_find_next_bus(const struct pci_bus *from);
 u16 pci_find_vsec_capability(struct pci_dev *dev, u16 vendor, int cap);
 u16 pci_find_dvsec_capability(struct pci_dev *dev, u16 vendor, u16 dvsec);
+u16 pci_find_next_dvsec_capability(struct pci_dev *dev, u16 start, u16 vendor,
+  u16 dvsec);
 
 u64 pci_get_dsn(struct pci_dev *dev);
 
-- 
2.20.1