[U-Boot] [PATCH] pci: Add comment to mention difference in DEVFN usage in U-Boot vs Linux
Stefan Roese
sr at denx.de
Mon Feb 11 07:43:25 UTC 2019
This patch adds a comment to the header with the PCI_foo macros related
to DEVFN to explain the difference in U-Boot vs Linux.
Signed-off-by: Stefan Roese <sr at denx.de>
Cc: Simon Glass <sjg at chromium.org>
Cc: Bin Meng <bmeng.cn at gmail.com>
---
include/pci.h | 11 +++++++++++
1 file changed, 11 insertions(+)
diff --git a/include/pci.h b/include/pci.h
index 041f8e3747..93fdd8fe6a 100644
--- a/include/pci.h
+++ b/include/pci.h
@@ -499,9 +499,20 @@ static inline void pci_set_region(struct pci_region *reg,
typedef int pci_dev_t;
#define PCI_BUS(d) (((d) >> 16) & 0xff)
+
+/*
+ * Please note the difference in DEVFN usage in U-Boot vs Linux. U-Boot
+ * uses DEVFN in bits 15-8 but Linux instead expects DEVFN in bits 7-0.
+ * Please see the Linux header include/uapi/linux/pci.h for more details.
+ * This is relevant for the following macros:
+ * PCI_DEV, PCI_FUNC, PCI_DEVFN
+ * The U-Boot macro PCI_DEV is equivalent to the Linux PCI_SLOT version with
+ * the remark from above (input d in bits 15-8 instead of 7-0.
+ */
#define PCI_DEV(d) (((d) >> 11) & 0x1f)
#define PCI_FUNC(d) (((d) >> 8) & 0x7)
#define PCI_DEVFN(d, f) ((d) << 11 | (f) << 8)
+
#define PCI_MASK_BUS(bdf) ((bdf) & 0xffff)
#define PCI_ADD_BUS(bus, devfn) (((bus) << 16) | (devfn))
#define PCI_BDF(b, d, f) ((b) << 16 | PCI_DEVFN(d, f))
--
2.20.1
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