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From: Philipp Stanner <pstanner@redhat.com>
To: Hans de Goede <hdegoede@redhat.com>,
	Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
	Maxime Ripard <mripard@kernel.org>,
	Thomas Zimmermann <tzimmermann@suse.de>,
	David Airlie <airlied@gmail.com>,
	Daniel Vetter <daniel@ffwll.ch>,
	Bjorn Helgaas <bhelgaas@google.com>,
	Sam Ravnborg <sam@ravnborg.org>,
	dakr@redhat.com
Cc: dri-devel@lists.freedesktop.org,
	linux-kernel@vger.kernel.org,
	linux-pci@vger.kernel.org,
	Philipp Stanner <pstanner@redhat.com>
Subject: [PATCH v6 03/10] PCI: Warn users about complicated devres nature
Date: Mon,  8 Apr 2024 10:44:15 +0200
Message-ID: <20240408084423.6697-4-pstanner@redhat.com>
In-Reply-To: <20240408084423.6697-1-pstanner@redhat.com>
References: <20240408084423.6697-1-pstanner@redhat.com>
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The PCI region-request functions become managed functions when
pcim_enable_device() has been called previously instead of
pci_enable_device().

This has already caused bugs by confusing users, who came to believe
that all pci functions, such as pci_iomap_range(), suddenly are managed
that way.

This is not the case.

Add comments to the relevant functions' docstrings that warn users about
this behavior.

Signed-off-by: Philipp Stanner <pstanner@redhat.com>
---
 drivers/pci/iomap.c | 18 ++++++++++++++
 drivers/pci/pci.c   | 60 ++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 77 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/iomap.c b/drivers/pci/iomap.c
index c9725428e387..ea3b9842132a 100644
--- a/drivers/pci/iomap.c
+++ b/drivers/pci/iomap.c
@@ -23,6 +23,11 @@
  *
  * @maxlen specifies the maximum length to map. If you want to get access to
  * the complete BAR from offset to the end, pass %0 here.
+ *
+ * NOTE:
+ * This function is never managed, even if you initialized with
+ * pcim_enable_device().
+ * If you need automatic cleanup, use pcim_iomap_range().
  * */
 void __iomem *pci_iomap_range(struct pci_dev *dev,
 			      int bar,
@@ -63,6 +68,10 @@ EXPORT_SYMBOL(pci_iomap_range);
  *
  * @maxlen specifies the maximum length to map. If you want to get access to
  * the complete BAR from offset to the end, pass %0 here.
+ *
+ * NOTE:
+ * This function is never managed, even if you initialized with
+ * pcim_enable_device().
  * */
 void __iomem *pci_iomap_wc_range(struct pci_dev *dev,
 				 int bar,
@@ -106,6 +115,11 @@ EXPORT_SYMBOL_GPL(pci_iomap_wc_range);
  *
  * @maxlen specifies the maximum length to map. If you want to get access to
  * the complete BAR without checking for its length first, pass %0 here.
+ *
+ * NOTE:
+ * This function is never managed, even if you initialized with
+ * pcim_enable_device().
+ * If you need automatic cleanup, use pcim_iomap().
  * */
 void __iomem *pci_iomap(struct pci_dev *dev, int bar, unsigned long maxlen)
 {
@@ -127,6 +141,10 @@ EXPORT_SYMBOL(pci_iomap);
  *
  * @maxlen specifies the maximum length to map. If you want to get access to
  * the complete BAR without checking for its length first, pass %0 here.
+ *
+ * NOTE:
+ * This function is never managed, even if you initialized with
+ * pcim_enable_device().
  * */
 void __iomem *pci_iomap_wc(struct pci_dev *dev, int bar, unsigned long maxlen)
 {
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index b5d21d8207d6..9d9d09534efe 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -3903,6 +3903,8 @@ EXPORT_SYMBOL(pci_release_region);
  * @res_name: Name to be associated with resource.
  * @exclusive: whether the region access is exclusive or not
  *
+ * Returns: 0 on success, negative error code on failure.
+ *
  * Mark the PCI region associated with PCI device @pdev BAR @bar as
  * being reserved by owner @res_name.  Do not access any
  * address inside the PCI regions unless this call returns
@@ -3914,6 +3916,13 @@ EXPORT_SYMBOL(pci_release_region);
  *
  * Returns 0 on success, or %EBUSY on error.  A warning
  * message is also printed on failure.
+ *
+ * NOTE:
+ * This is a "hybrid" function: Its normally unmanaged, but becomes managed
+ * when pcim_enable_device() has been called in advance.
+ * This hybrid feature is DEPRECATED! If you need to implement a new pci
+ * function that does automatic cleanup, write a new pcim_* function that uses
+ * devres directly.
  */
 static int __pci_request_region(struct pci_dev *pdev, int bar,
 				const char *res_name, int exclusive)
@@ -3962,6 +3971,8 @@ static int __pci_request_region(struct pci_dev *pdev, int bar,
  * @bar: BAR to be reserved
  * @res_name: Name to be associated with resource
  *
+ * Returns: 0 on success, negative error code on failure.
+ *
  * Mark the PCI region associated with PCI device @pdev BAR @bar as
  * being reserved by owner @res_name.  Do not access any
  * address inside the PCI regions unless this call returns
@@ -3969,6 +3980,12 @@ static int __pci_request_region(struct pci_dev *pdev, int bar,
  *
  * Returns 0 on success, or %EBUSY on error.  A warning
  * message is also printed on failure.
+ *
+ * NOTE:
+ * This is a "hybrid" function: Its normally unmanaged, but becomes managed
+ * when pcim_enable_device() has been called in advance.
+ * This hybrid feature is DEPRECATED! If you want managed cleanup, use the
+ * pcim_* functions instead.
  */
 int pci_request_region(struct pci_dev *pdev, int bar, const char *res_name)
 {
@@ -3994,6 +4011,13 @@ void pci_release_selected_regions(struct pci_dev *pdev, int bars)
 }
 EXPORT_SYMBOL(pci_release_selected_regions);
 
+/*
+ * NOTE:
+ * This is a "hybrid" function: Its normally unmanaged, but becomes managed
+ * when pcim_enable_device() has been called in advance.
+ * This hybrid feature is DEPRECATED! If you want managed cleanup, use the
+ * pcim_* functions instead.
+ */
 static int __pci_request_selected_regions(struct pci_dev *pdev, int bars,
 					  const char *res_name, int excl)
 {
@@ -4019,6 +4043,14 @@ static int __pci_request_selected_regions(struct pci_dev *pdev, int bars,
  * @pdev: PCI device whose resources are to be reserved
  * @bars: Bitmask of BARs to be requested
  * @res_name: Name to be associated with resource
+ *
+ * Returns: 0 on success, negative error code on failure.
+ *
+ * NOTE:
+ * This is a "hybrid" function: Its normally unmanaged, but becomes managed
+ * when pcim_enable_device() has been called in advance.
+ * This hybrid feature is DEPRECATED! If you want managed cleanup, use the
+ * pcim_* functions instead.
  */
 int pci_request_selected_regions(struct pci_dev *pdev, int bars,
 				 const char *res_name)
@@ -4027,6 +4059,20 @@ int pci_request_selected_regions(struct pci_dev *pdev, int bars,
 }
 EXPORT_SYMBOL(pci_request_selected_regions);
 
+/**
+ * pci_request_selected_regions_exclusive - Request regions exclusively
+ * @pdev: PCI device to request regions from
+ * @bars: bit mask of bars to request
+ * @res_name: name to be associated with the requests
+ *
+ * Returns: 0 on success, negative error code on failure.
+ *
+ * NOTE:
+ * This is a "hybrid" function: Its normally unmanaged, but becomes managed
+ * when pcim_enable_device() has been called in advance.
+ * This hybrid feature is DEPRECATED! If you want managed cleanup, use the
+ * pcim_* functions instead.
+ */
 int pci_request_selected_regions_exclusive(struct pci_dev *pdev, int bars,
 					   const char *res_name)
 {
@@ -4044,7 +4090,6 @@ EXPORT_SYMBOL(pci_request_selected_regions_exclusive);
  * successful call to pci_request_regions().  Call this function only
  * after all use of the PCI regions has ceased.
  */
-
 void pci_release_regions(struct pci_dev *pdev)
 {
 	pci_release_selected_regions(pdev, (1 << PCI_STD_NUM_BARS) - 1);
@@ -4076,6 +4121,8 @@ EXPORT_SYMBOL(pci_request_regions);
  * @pdev: PCI device whose resources are to be reserved
  * @res_name: Name to be associated with resource.
  *
+ * Returns: 0 on success, negative error code on failure.
+ *
  * Mark all PCI regions associated with PCI device @pdev as being reserved
  * by owner @res_name.  Do not access any address inside the PCI regions
  * unless this call returns successfully.
@@ -4085,6 +4132,12 @@ EXPORT_SYMBOL(pci_request_regions);
  *
  * Returns 0 on success, or %EBUSY on error.  A warning message is also
  * printed on failure.
+ *
+ * NOTE:
+ * This is a "hybrid" function: Its normally unmanaged, but becomes managed
+ * when pcim_enable_device() has been called in advance.
+ * This hybrid feature is DEPRECATED! If you want managed cleanup, use the
+ * pcim_* functions instead.
  */
 int pci_request_regions_exclusive(struct pci_dev *pdev, const char *res_name)
 {
@@ -4416,6 +4469,11 @@ void pci_disable_parity(struct pci_dev *dev)
  * @enable: boolean: whether to enable or disable PCI INTx
  *
  * Enables/disables PCI INTx for device @pdev
+ *
+ * NOTE:
+ * This is a "hybrid" function: Its normally unmanaged, but becomes managed
+ * when pcim_enable_device() has been called in advance.
+ * This hybrid feature is DEPRECATED!
  */
 void pci_intx(struct pci_dev *pdev, int enable)
 {
-- 
2.44.0