From b3ca84e3c66a4506ac08985bd72c8f255a7d6978 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Pali=20Roh=C3=A1r?= Date: Wed, 4 May 2022 18:57:26 +0200 Subject: [PATCH] PCI: pci-bridge-emul: Add description for class_revision field MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit commit 9319230ac147067652b58fe849ffe0ceec098665 upstream. The current assignment to the class_revision member class_revision |= cpu_to_le32(PCI_CLASS_BRIDGE_PCI << 16); can make the reader think that class is at high 16 bits of the member and revision at low 16 bits. In reality, class is at high 24 bits, but the class for PCI Bridge Normal Decode is PCI_CLASS_BRIDGE_PCI << 8. Change the assignment and add a comment to make this clearer. Link: https://lore.kernel.org/r/20211130172913.9727-2-kabel@kernel.org Signed-off-by: Pali Rohár Signed-off-by: Marek Behún Signed-off-by: Lorenzo Pieralisi Signed-off-by: Marek Behún Signed-off-by: Greg Kroah-Hartman --- drivers/pci/pci-bridge-emul.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/drivers/pci/pci-bridge-emul.c b/drivers/pci/pci-bridge-emul.c index 37504c2..0a4e713 100644 --- a/drivers/pci/pci-bridge-emul.c +++ b/drivers/pci/pci-bridge-emul.c @@ -284,7 +284,11 @@ int pci_bridge_emul_init(struct pci_bridge_emul *bridge, { BUILD_BUG_ON(sizeof(bridge->conf) != PCI_BRIDGE_CONF_END); - bridge->conf.class_revision |= cpu_to_le32(PCI_CLASS_BRIDGE_PCI << 16); + /* + * class_revision: Class is high 24 bits and revision is low 8 bit of this member, + * while class for PCI Bridge Normal Decode has the 24-bit value: PCI_CLASS_BRIDGE_PCI << 8 + */ + bridge->conf.class_revision |= cpu_to_le32((PCI_CLASS_BRIDGE_PCI << 8) << 8); bridge->conf.header_type = PCI_HEADER_TYPE_BRIDGE; bridge->conf.cache_line_size = 0x10; bridge->conf.status = cpu_to_le16(PCI_STATUS_CAP_LIST); -- 2.7.4