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PCI/MSI: Clarify pci_free_irq_vectors() usage for managed devices 

Update pci_free_irq_vectors() documentation to clarify that drivers using
pcim_enable_device() must not call pci_free_irq_vectors().

For legacy reasons, pcim_enable_device() switches several normally
un-managed functions into managed mode. Currently, the only function
affected in this way is pcim_setup_msi_release(), which results in
automatic IRQ vector management.

This behavior is dangerous and confusing. Drivers using pcim_enable_device()
should rely on the automatic IRQ vector management and avoid calling
pci_free_irq_vectors() manually.

Suggested-by: Philipp Stanner <phasta@kernel.org>
Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
[bhelgaas: squash both updates to pci_free_irq_vectors() documentation]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://patch.msgid.link/1770798299-202288-2-git-send-email-shawn.lin@rock-chips.com
Link: https://patch.msgid.link/1770798299-202288-3-git-send-email-shawn.lin@rock-chips.com
master
Shawn Lin 2026-02-11 16:24:57 +08:00 committed by Bjorn Helgaas
parent 6de23f81a5
commit 03e4905402
2 changed files with 10 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
Documentation/PCI/msi-howto.rst
View File

@ -113,8 +113,11 @@ vectors, use the following function::
int pci_irq_vector(struct pci_dev *dev, unsigned int nr);
Any allocated resources should be freed before removing the device using
the following function::
If the driver enables the device using pcim_enable_device(), the driver
shouldn't call pci_free_irq_vectors() because pcim_enable_device()
activates automatic management for IRQ vectors. Otherwise, the driver should
free any allocated IRQ vectors before removing the device using the following
function::
void pci_free_irq_vectors(struct pci_dev *dev);

5
drivers/pci/msi/api.c
View File

@ -370,6 +370,11 @@ EXPORT_SYMBOL(pci_irq_get_affinity);
* Undo the interrupt vector allocations and possible device MSI/MSI-X
* enablement earlier done through pci_alloc_irq_vectors_affinity() or
* pci_alloc_irq_vectors().
*
* WARNING: Do not call this function if the device has been enabled
* with pcim_enable_device(). In that case, IRQ vectors are automatically
* managed via pcim_msi_release() and calling pci_free_irq_vectors() can
* lead to double-free issues.
*/
void pci_free_irq_vectors(struct pci_dev *dev)
{