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Message-Id: <20251109-remove_cap-v1-1-2208f46f4dc2@oss.qualcomm.com>
Date: Sun, 09 Nov 2025 22:59:40 -0800
From: Qiang Yu <qiang.yu@....qualcomm.com>
To: Lorenzo Pieralisi <lpieralisi@...nel.org>,
Krzysztof Wilczyński <kwilczynski@...nel.org>,
Manivannan Sadhasivam <mani@...nel.org>, Rob Herring <robh@...nel.org>,
Bjorn Helgaas <bhelgaas@...gle.com>, Jingoo Han <jingoohan1@...il.com>
Cc: linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-arm-msm@...r.kernel.org, Qiang Yu <qiang.yu@....qualcomm.com>
Subject: [PATCH 1/5] PCI: Add preceding capability position support and
update drivers
Add support for finding the preceding capability position in PCI
capability list by extending the capability finding macros with an
additional parameter. This functionality is essential for modifying PCI
capability list, as it provides the necessary information to update the
"next" pointer of the predecessor capability when removing entries.
Modify two macros to accept a new 'prev_ptr' parameter:
- PCI_FIND_NEXT_CAP - Now accepts 'prev_ptr' parameter for standard
capabilities
- PCI_FIND_NEXT_EXT_CAP - Now accepts 'prev_ptr' parameter for extended
capabilities
When a capability is found, these macros:
- Store the position of the preceding capability in *prev_ptr
(if prev_ptr != NULL)
- Maintain all existing functionality when prev_ptr is NULL
Update current callers to accommodate this API
change:
- Cadence PCIe controller: Pass NULL to cdns_pcie_find_capability() and
cdns_pcie_find_ext_capability() calls
- DesignWare PCIe controller: Pass NULL to all capability finding macro
calls
The drivers pass NULL as the prev_ptr parameter since they don't require
knowledge of the preceding capability position for their current
functionality. This ensures backward compatibility while enabling future
capability list manipulation features.
No functional changes to driver behavior result from this patch - it
maintains the existing capability finding functionality while adding the
infrastructure for future capability removal operations.
Signed-off-by: Qiang Yu <qiang.yu@....qualcomm.com>
---
drivers/pci/controller/cadence/pcie-cadence.c | 4 ++--
drivers/pci/controller/dwc/pcie-designware-ep.c | 2 +-
drivers/pci/controller/dwc/pcie-designware.c | 6 +++---
drivers/pci/pci.c | 8 ++++----
drivers/pci/pci.h | 23 +++++++++++++++++++----
5 files changed, 29 insertions(+), 14 deletions(-)
diff --git a/drivers/pci/controller/cadence/pcie-cadence.c b/drivers/pci/controller/cadence/pcie-cadence.c
index bd683d0fecb225f2134893faa7199d659157b3f1..d614452861f7755108b1220527dc277a3754a76d 100644
--- a/drivers/pci/controller/cadence/pcie-cadence.c
+++ b/drivers/pci/controller/cadence/pcie-cadence.c
@@ -13,13 +13,13 @@
u8 cdns_pcie_find_capability(struct cdns_pcie *pcie, u8 cap)
{
return PCI_FIND_NEXT_CAP(cdns_pcie_read_cfg, PCI_CAPABILITY_LIST,
- cap, pcie);
+ cap, NULL, pcie);
}
EXPORT_SYMBOL_GPL(cdns_pcie_find_capability);
u16 cdns_pcie_find_ext_capability(struct cdns_pcie *pcie, u8 cap)
{
- return PCI_FIND_NEXT_EXT_CAP(cdns_pcie_read_cfg, 0, cap, pcie);
+ return PCI_FIND_NEXT_EXT_CAP(cdns_pcie_read_cfg, 0, cap, NULL, pcie);
}
EXPORT_SYMBOL_GPL(cdns_pcie_find_ext_capability);
diff --git a/drivers/pci/controller/dwc/pcie-designware-ep.c b/drivers/pci/controller/dwc/pcie-designware-ep.c
index 7f2112c2fb21543d11e848a4a62d529cc3f4e8d0..e62665e228b9035f35c441bffd2a5759ecf12546 100644
--- a/drivers/pci/controller/dwc/pcie-designware-ep.c
+++ b/drivers/pci/controller/dwc/pcie-designware-ep.c
@@ -72,7 +72,7 @@ EXPORT_SYMBOL_GPL(dw_pcie_ep_reset_bar);
static u8 dw_pcie_ep_find_capability(struct dw_pcie_ep *ep, u8 func_no, u8 cap)
{
return PCI_FIND_NEXT_CAP(dw_pcie_ep_read_cfg, PCI_CAPABILITY_LIST,
- cap, ep, func_no);
+ cap, NULL, ep, func_no);
}
/**
diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
index c644216995f69cbf065e61a0392bf1e5e32cf56e..5585d3ed74316bd218572484f6320019db8d6a10 100644
--- a/drivers/pci/controller/dwc/pcie-designware.c
+++ b/drivers/pci/controller/dwc/pcie-designware.c
@@ -224,13 +224,13 @@ void dw_pcie_version_detect(struct dw_pcie *pci)
u8 dw_pcie_find_capability(struct dw_pcie *pci, u8 cap)
{
return PCI_FIND_NEXT_CAP(dw_pcie_read_cfg, PCI_CAPABILITY_LIST, cap,
- pci);
+ NULL, pci);
}
EXPORT_SYMBOL_GPL(dw_pcie_find_capability);
u16 dw_pcie_find_ext_capability(struct dw_pcie *pci, u8 cap)
{
- return PCI_FIND_NEXT_EXT_CAP(dw_pcie_read_cfg, 0, cap, pci);
+ return PCI_FIND_NEXT_EXT_CAP(dw_pcie_read_cfg, 0, cap, NULL, pci);
}
EXPORT_SYMBOL_GPL(dw_pcie_find_ext_capability);
@@ -244,7 +244,7 @@ static u16 __dw_pcie_find_vsec_capability(struct dw_pcie *pci, u16 vendor_id,
return 0;
while ((vsec = PCI_FIND_NEXT_EXT_CAP(dw_pcie_read_cfg, vsec,
- PCI_EXT_CAP_ID_VNDR, pci))) {
+ PCI_EXT_CAP_ID_VNDR, NULL, pci))) {
header = dw_pcie_readl_dbi(pci, vsec + PCI_VNDR_HEADER);
if (PCI_VNDR_HEADER_ID(header) == vsec_id)
return vsec;
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index b14dd064006cca80ec5275e45a35d6dc2b4d0bbc..83e3252f6691f2289ab5cacc3346a37c69a13d59 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -426,7 +426,7 @@ static int pci_dev_str_match(struct pci_dev *dev, const char *p,
static u8 __pci_find_next_cap(struct pci_bus *bus, unsigned int devfn,
u8 pos, int cap)
{
- return PCI_FIND_NEXT_CAP(pci_bus_read_config, pos, cap, bus, devfn);
+ return PCI_FIND_NEXT_CAP(pci_bus_read_config, pos, cap, NULL, bus, devfn);
}
u8 pci_find_next_capability(struct pci_dev *dev, u8 pos, int cap)
@@ -531,7 +531,7 @@ u16 pci_find_next_ext_capability(struct pci_dev *dev, u16 start, int cap)
return 0;
return PCI_FIND_NEXT_EXT_CAP(pci_bus_read_config, start, cap,
- dev->bus, dev->devfn);
+ NULL, dev->bus, dev->devfn);
}
EXPORT_SYMBOL_GPL(pci_find_next_ext_capability);
@@ -600,7 +600,7 @@ static u8 __pci_find_next_ht_cap(struct pci_dev *dev, u8 pos, int ht_cap)
mask = HT_5BIT_CAP_MASK;
pos = PCI_FIND_NEXT_CAP(pci_bus_read_config, pos,
- PCI_CAP_ID_HT, dev->bus, dev->devfn);
+ PCI_CAP_ID_HT, NULL, dev->bus, dev->devfn);
while (pos) {
rc = pci_read_config_byte(dev, pos + 3, &cap);
if (rc != PCIBIOS_SUCCESSFUL)
@@ -611,7 +611,7 @@ static u8 __pci_find_next_ht_cap(struct pci_dev *dev, u8 pos, int ht_cap)
pos = PCI_FIND_NEXT_CAP(pci_bus_read_config,
pos + PCI_CAP_LIST_NEXT,
- PCI_CAP_ID_HT, dev->bus,
+ PCI_CAP_ID_HT, NULL, dev->bus,
dev->devfn);
}
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 4492b809094b5794bd94dfbc20102cb208c3fa2f..2a33356acc2e8cfe55801bcb7d0cd6d2a336561b 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -103,17 +103,21 @@ bool pcie_cap_has_rtctl(const struct pci_dev *dev);
* @read_cfg: Function pointer for reading PCI config space
* @start: Starting position to begin search
* @cap: Capability ID to find
+ * @prev_ptr: Pointer to store position of preceding capability (optional)
* @args: Arguments to pass to read_cfg function
*
- * Search the capability list in PCI config space to find @cap.
+ * Search the capability list in PCI config space to find @cap. If
+ * found, update *prev_ptr with the position of the preceding capability
+ * (if prev_ptr != NULL)
* Implements TTL (time-to-live) protection against infinite loops.
*
* Return: Position of the capability if found, 0 otherwise.
*/
-#define PCI_FIND_NEXT_CAP(read_cfg, start, cap, args...) \
+#define PCI_FIND_NEXT_CAP(read_cfg, start, cap, prev_ptr, args...) \
({ \
int __ttl = PCI_FIND_CAP_TTL; \
- u8 __id, __found_pos = 0; \
+ u8 __id, __found_pos = 0; \
+ u8 __prev_pos = (start); \
u8 __pos = (start); \
u16 __ent; \
\
@@ -132,9 +136,12 @@ bool pcie_cap_has_rtctl(const struct pci_dev *dev);
\
if (__id == (cap)) { \
__found_pos = __pos; \
+ if (prev_ptr != NULL) \
+ *(u8 *)prev_ptr = __prev_pos; \
break; \
} \
\
+ __prev_pos = __pos; \
__pos = FIELD_GET(PCI_CAP_LIST_NEXT_MASK, __ent); \
} \
__found_pos; \
@@ -146,21 +153,26 @@ bool pcie_cap_has_rtctl(const struct pci_dev *dev);
* @read_cfg: Function pointer for reading PCI config space
* @start: Starting position to begin search (0 for initial search)
* @cap: Extended capability ID to find
+ * @prev_ptr: Pointer to store position of preceding capability (optional)
* @args: Arguments to pass to read_cfg function
*
* Search the extended capability list in PCI config space to find @cap.
+ * If found, update *prev_ptr with the position of the preceding capability
+ * (if prev_ptr != NULL)
* Implements TTL protection against infinite loops using a calculated
* maximum search count.
*
* Return: Position of the capability if found, 0 otherwise.
*/
-#define PCI_FIND_NEXT_EXT_CAP(read_cfg, start, cap, args...) \
+#define PCI_FIND_NEXT_EXT_CAP(read_cfg, start, cap, prev_ptr, args...) \
({ \
u16 __pos = (start) ?: PCI_CFG_SPACE_SIZE; \
u16 __found_pos = 0; \
+ u16 __prev_pos; \
int __ttl, __ret; \
u32 __header; \
\
+ __prev_pos = __pos; \
__ttl = (PCI_CFG_SPACE_EXP_SIZE - PCI_CFG_SPACE_SIZE) / 8; \
while (__ttl-- > 0 && __pos >= PCI_CFG_SPACE_SIZE) { \
__ret = read_cfg##_dword(args, __pos, &__header); \
@@ -172,9 +184,12 @@ bool pcie_cap_has_rtctl(const struct pci_dev *dev);
\
if (PCI_EXT_CAP_ID(__header) == (cap) && __pos != start) {\
__found_pos = __pos; \
+ if (prev_ptr != NULL) \
+ *(u16 *)prev_ptr = __prev_pos; \
break; \
} \
\
+ __prev_pos = __pos; \
__pos = PCI_EXT_CAP_NEXT(__header); \
} \
__found_pos; \
--
2.34.1
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