PCI/sysfs: Fix read byte order in pci_read_legacy_io()

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pci_read_legacy_io() passes the sysfs buffer directly to pci_legacy_read():

  return pci_legacy_read(bus, off, (u32 *)buf, count);

The PowerPC implementation stores the result as a native-endian integer:

  *((u16 *)val) = in_le16(addr);

On big-endian PowerPC this stores the bytes in the wrong order, so
a 2-byte read of a device register returns different bytes than two
1-byte reads at the same addresses.  The same applies to 4-byte
reads.  On little-endian the native byte order already matches PCI
I/O port byte order, so the conversion is a no-op.

Thus, let pci_legacy_read() store into a local u32 variable, then
copy the I/O port value to the sysfs buffer using put_unaligned_le16()
and put_unaligned_le32() for the 2 and 4 byte cases, converting from
the native integer to little-endian byte order matching PCI I/O port
space.

No changes are needed for the Alpha platform.

The legacy_io file is root-only and exists only on Alpha and PowerPC,
the two architectures that define HAVE_PCI_LEGACY.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260616163131.2763281-2-kwilczynski@kernel.org
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>

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This commit is contained in:

Krzysztof Wilczyński 2026-06-16 16:31:31 +00:00

parent dc76258d01

commit 5b95212de6

1 changed files with 19 additions and 1 deletions

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drivers/pci/pci-sysfs.c

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