[PATCH v2 0/2] Introduce pci_find_next_dvsec_capability() to simplify the code

[PATCH v2 0/2] Introduce pci_find_next_dvsec_capability() to simplify the code

[Xiongfeng Wang]

Some devices may have several DVSEC (Designated Vendor-Specific Extended
Capability) entries with the same DVSEC ID. Introduce
pci_find_next_dvsec_capability() to simplify the code.

ChangeLog:
v1->v2:  Add Reviewed-by and Acked-by tags
	 Modify commit message and document a little for the first patch

Xiongfeng Wang (2):
  PCI: Add pci_find_next_dvsec_capability to find next Designated VSEC
  ocxl: use pci_find_next_dvsec_capability() to simplify the code

 arch/powerpc/platforms/powernv/ocxl.c | 20 ++------------
 drivers/misc/ocxl/config.c            | 21 +++++----------
 drivers/pci/pci.c                     | 39 ++++++++++++++++++---------
 include/linux/pci.h                   |  2 ++
 include/misc/ocxl-config.h            |  4 ---
 5 files changed, 36 insertions(+), 50 deletions(-)

-- 
2.20.1

[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 <wangxiongfeng2@huawei.com>
Reviewed-by: Andrew Donnellan <ajd@linux.ibm.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
---
 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, &v);
 		pci_read_config_word(dev, pos + PCI_DVSEC_HEADER2, &id);
 		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

[PATCH v2 2/2] ocxl: use pci_find_next_dvsec_capability() to simplify the code

[Xiongfeng Wang]

PCI core add pci_find_next_dvsec_capability() to query the next DVSEC.
We can use that core API to simplify the code. Also remove the unused
macros.

Signed-off-by: Xiongfeng Wang <wangxiongfeng2@huawei.com>
Reviewed-by: Andrew Donnellan <ajd@linux.ibm.com>
---
 arch/powerpc/platforms/powernv/ocxl.c | 20 ++------------------
 drivers/misc/ocxl/config.c            | 21 ++++++---------------
 include/misc/ocxl-config.h            |  4 ----
 3 files changed, 8 insertions(+), 37 deletions(-)

diff --git a/arch/powerpc/platforms/powernv/ocxl.c b/arch/powerpc/platforms/powernv/ocxl.c
index 629067781cec..8dbc1a9535fc 100644
--- a/arch/powerpc/platforms/powernv/ocxl.c
+++ b/arch/powerpc/platforms/powernv/ocxl.c
@@ -71,29 +71,13 @@ static DEFINE_MUTEX(links_list_lock);
  * the AFUs, by pro-rating if needed.
  */
 
-static int find_dvsec_from_pos(struct pci_dev *dev, int dvsec_id, int pos)
-{
-	int vsec = pos;
-	u16 vendor, id;
-
-	while ((vsec = pci_find_next_ext_capability(dev, vsec,
-						    OCXL_EXT_CAP_ID_DVSEC))) {
-		pci_read_config_word(dev, vsec + OCXL_DVSEC_VENDOR_OFFSET,
-				&vendor);
-		pci_read_config_word(dev, vsec + OCXL_DVSEC_ID_OFFSET, &id);
-		if (vendor == PCI_VENDOR_ID_IBM && id == dvsec_id)
-			return vsec;
-	}
-	return 0;
-}
-
 static int find_dvsec_afu_ctrl(struct pci_dev *dev, u8 afu_idx)
 {
 	int vsec = 0;
 	u8 idx;
 
-	while ((vsec = find_dvsec_from_pos(dev, OCXL_DVSEC_AFU_CTRL_ID,
-					   vsec))) {
+	while ((vsec = pci_find_next_dvsec_capability(dev, vsec,
+				PCI_VENDOR_ID_IBM, OCXL_DVSEC_AFU_CTRL_ID))) {
 		pci_read_config_byte(dev, vsec + OCXL_DVSEC_AFU_CTRL_AFU_IDX,
 				&idx);
 		if (idx == afu_idx)
diff --git a/drivers/misc/ocxl/config.c b/drivers/misc/ocxl/config.c
index 92ab49705f64..6c0fca32e6db 100644
--- a/drivers/misc/ocxl/config.c
+++ b/drivers/misc/ocxl/config.c
@@ -39,23 +39,14 @@ static int find_dvsec(struct pci_dev *dev, int dvsec_id)
 static int find_dvsec_afu_ctrl(struct pci_dev *dev, u8 afu_idx)
 {
 	int vsec = 0;
-	u16 vendor, id;
 	u8 idx;
 
-	while ((vsec = pci_find_next_ext_capability(dev, vsec,
-						    OCXL_EXT_CAP_ID_DVSEC))) {
-		pci_read_config_word(dev, vsec + OCXL_DVSEC_VENDOR_OFFSET,
-				&vendor);
-		pci_read_config_word(dev, vsec + OCXL_DVSEC_ID_OFFSET, &id);
-
-		if (vendor == PCI_VENDOR_ID_IBM &&
-			id == OCXL_DVSEC_AFU_CTRL_ID) {
-			pci_read_config_byte(dev,
-					vsec + OCXL_DVSEC_AFU_CTRL_AFU_IDX,
-					&idx);
-			if (idx == afu_idx)
-				return vsec;
-		}
+	while ((vsec = pci_find_next_dvsec_capability(dev, vsec,
+				PCI_VENDOR_ID_IBM, OCXL_DVSEC_AFU_CTRL_ID))) {
+		pci_read_config_byte(dev, vsec + OCXL_DVSEC_AFU_CTRL_AFU_IDX,
+				     &idx);
+		if (idx == afu_idx)
+			return vsec;
 	}
 	return 0;
 }
diff --git a/include/misc/ocxl-config.h b/include/misc/ocxl-config.h
index ccfd3b463517..40cf1b143170 100644
--- a/include/misc/ocxl-config.h
+++ b/include/misc/ocxl-config.h
@@ -10,10 +10,6 @@
  * It follows the specification for opencapi 3.0
  */
 
-#define OCXL_EXT_CAP_ID_DVSEC                 0x23
-
-#define OCXL_DVSEC_VENDOR_OFFSET              0x4
-#define OCXL_DVSEC_ID_OFFSET                  0x8
 #define OCXL_DVSEC_TL_ID                      0xF000
 #define   OCXL_DVSEC_TL_BACKOFF_TIMERS          0x10
 #define   OCXL_DVSEC_TL_RECV_CAP                0x18
-- 
2.20.1

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.