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| author | Danilo Krummrich <dakr@kernel.org> | 2026-08-13 18:52:04 +0200 |
|---|---|---|
| committer | Danilo Krummrich <dakr@kernel.org> | 2026-08-17 01:41:36 +0200 |
| commit | f146c7bc85a51f95c05e0f8173d484eb301ece78 (patch) | |
| tree | 07296ae54ed6551492b0c609dc0f5463f61f89ca /Documentation/userspace-api/ioctl/ioctl-decoding.rst | |
| download | linux-stable-f146c7bc85a51f95c05e0f8173d484eb301ece78.tar.gz linux-stable-f146c7bc85a51f95c05e0f8173d484eb301ece78.zip | |
PCI: Add pci_irq_type() to query the allocated interrupt typegrafted
Add a helper that returns PCI_IRQ_MSIX, PCI_IRQ_MSI, or PCI_IRQ_INTX
based on the interrupt type the PCI core selected after
pci_alloc_irq_vectors().
Several drivers already open-code this check against pdev->msix_enabled
and pdev->msi_enabled, or even open code this helper [1].
A common helper avoids the duplication and keeps drivers from accessing
the bitfield directly (see also [2]).
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Tested-by: John Hubbard <jhubbard@nvidia.com>
Link: https://elixir.bootlin.com/linux/v7.1/source/drivers/net/ethernet/aquantia/atlantic/aq_pci_func.c#L196 [1]
Inspired-by: John Hubbard <jhubbard@nvidia.com>
Link: https://lore.kernel.org/all/DKKG2QM3YJYB.Z2H2B2UXJ75N@kernel.org/ [2]
Reviewed-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260813165234.620555-5-dakr@kernel.org
[ Add missing pci_irq_type() stub for CONFIG_PCI=n. ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
Diffstat (limited to 'Documentation/userspace-api/ioctl/ioctl-decoding.rst')
| -rw-r--r-- | Documentation/userspace-api/ioctl/ioctl-decoding.rst | 31 |
1 files changed, 31 insertions, 0 deletions
diff --git a/Documentation/userspace-api/ioctl/ioctl-decoding.rst b/Documentation/userspace-api/ioctl/ioctl-decoding.rst new file mode 100644 index 000000000..380d6bb3e --- /dev/null +++ b/Documentation/userspace-api/ioctl/ioctl-decoding.rst @@ -0,0 +1,31 @@ +============================== +Decoding an IOCTL Magic Number +============================== + +To decode a hex IOCTL code: + +Most architectures use this generic format, but check +include/ARCH/ioctl.h for specifics, e.g. powerpc +uses 3 bits to encode read/write and 13 bits for size. + + ====== ================================== + bits meaning + ====== ================================== + 31-30 00 - no parameters: uses _IO macro + 10 - read: _IOR + 01 - write: _IOW + 11 - read/write: _IOWR + + 29-16 size of arguments + + 15-8 ascii character supposedly + unique to each driver + + 7-0 function # + ====== ================================== + + +So for example 0x82187201 is a read with arg length of 0x218, +character 'r' function 1. Grepping the source reveals this is:: + + #define VFAT_IOCTL_READDIR_BOTH _IOR('r', 1, struct dirent [2]) |