[RFC PATCH 01/13] PCI: Prepare removing devres from pci_intx()

[Philipp Stanner]

pci_intx() is a hybrid function which sometimes performs devres
operations, depending on whether pcim_enable_device() has been used to
enable the pci_dev. This sometimes-managed nature of the function is
problematic. Notably, it causes the function to allocate under some
circumstances which makes it unusable from interrupt context.

To, ultimately, remove the hybrid nature from pci_intx(), it is first
necessary to provide an always-managed and a never-managed version
of that function. Then, all callers of pci_intx() can be ported to the
version they need, depending whether they use pci_enable_device() or
pcim_enable_device().

An always-managed function exists, namely pcim_intx(), for which
__pcim_intx(), a never-managed version of pci_intx() had been
implemented.

Make __pcim_intx() a public function under the name
pci_intx_unmanaged(). Make pcim_intx() a public function.

Signed-off-by: Philipp Stanner <pstanner@xxxxxxxxxx>
---
 drivers/pci/devres.c | 24 +++---------------------
 drivers/pci/pci.c    | 26 ++++++++++++++++++++++++++
 include/linux/pci.h  |  2 ++
 3 files changed, 31 insertions(+), 21 deletions(-)

diff --git a/drivers/pci/devres.c b/drivers/pci/devres.c
index b133967faef8..475a3ae5c33f 100644
--- a/drivers/pci/devres.c
+++ b/drivers/pci/devres.c
@@ -411,31 +411,12 @@ static inline bool mask_contains_bar(int mask, int bar)
 	return mask & BIT(bar);
 }
 
-/*
- * This is a copy of pci_intx() used to bypass the problem of recursive
- * function calls due to the hybrid nature of pci_intx().
- */
-static void __pcim_intx(struct pci_dev *pdev, int enable)
-{
-	u16 pci_command, new;
-
-	pci_read_config_word(pdev, PCI_COMMAND, &pci_command);
-
-	if (enable)
-		new = pci_command & ~PCI_COMMAND_INTX_DISABLE;
-	else
-		new = pci_command | PCI_COMMAND_INTX_DISABLE;
-
-	if (new != pci_command)
-		pci_write_config_word(pdev, PCI_COMMAND, new);
-}
-
 static void pcim_intx_restore(struct device *dev, void *data)
 {
 	struct pci_dev *pdev = to_pci_dev(dev);
 	struct pcim_intx_devres *res = data;
 
-	__pcim_intx(pdev, res->orig_intx);
+	pci_intx_unmanaged(pdev, res->orig_intx);
 }
 
 static struct pcim_intx_devres *get_or_create_intx_devres(struct device *dev)
@@ -472,10 +453,11 @@ int pcim_intx(struct pci_dev *pdev, int enable)
 		return -ENOMEM;
 
 	res->orig_intx = !enable;
-	__pcim_intx(pdev, enable);
+	pci_intx_unmanaged(pdev, enable);
 
 	return 0;
 }
+EXPORT_SYMBOL(pcim_intx);
 
 static void pcim_disable_device(void *pdev_raw)
 {
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 7d85c04fbba2..318cfb5b5e15 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -4476,6 +4476,32 @@ void pci_disable_parity(struct pci_dev *dev)
 	}
 }
 
+/**
+ * pci_intx - enables/disables PCI INTx for device dev, unmanaged version
+ * @pdev: the PCI device to operate on
+ * @enable: boolean: whether to enable or disable PCI INTx
+ *
+ * Enables/disables PCI INTx for device @pdev
+ *
+ * This function behavios identically to pci_intx(), but is never managed with
+ * devres.
+ */
+void pci_intx_unmanaged(struct pci_dev *pdev, int enable)
+{
+	u16 pci_command, new;
+
+	pci_read_config_word(pdev, PCI_COMMAND, &pci_command);
+
+	if (enable)
+		new = pci_command & ~PCI_COMMAND_INTX_DISABLE;
+	else
+		new = pci_command | PCI_COMMAND_INTX_DISABLE;
+
+	if (new != pci_command)
+		pci_write_config_word(pdev, PCI_COMMAND, new);
+}
+EXPORT_SYMBOL_GPL(pci_intx_unmanaged);
+
 /**
  * pci_intx - enables/disables PCI INTx for device dev
  * @pdev: the PCI device to operate on
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 573b4c4c2be6..6b8cde76d564 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1353,6 +1353,7 @@ int __must_check pcim_set_mwi(struct pci_dev *dev);
 int pci_try_set_mwi(struct pci_dev *dev);
 void pci_clear_mwi(struct pci_dev *dev);
 void pci_disable_parity(struct pci_dev *dev);
+void pci_intx_unmanaged(struct pci_dev *pdev, int enable);
 void pci_intx(struct pci_dev *dev, int enable);
 bool pci_check_and_mask_intx(struct pci_dev *dev);
 bool pci_check_and_unmask_intx(struct pci_dev *dev);
@@ -2293,6 +2294,7 @@ static inline void pci_fixup_device(enum pci_fixup_pass pass,
 				    struct pci_dev *dev) { }
 #endif
 
+int pcim_intx(struct pci_dev *pdev, int enabled);
 void __iomem *pcim_iomap(struct pci_dev *pdev, int bar, unsigned long maxlen);
 void __iomem *pcim_iomap_region(struct pci_dev *pdev, int bar,
 				const char *name);
-- 
2.46.1