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pci: Add comment to mention difference in DEVFN usage in U-Boot vs Linux

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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@denx.de>
Cc: Simon Glass <sjg@chromium.org>
Cc: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
This commit is contained in:
Stefan Roese 2019-02-11 08:43:25 +01:00 committed by Tom Rini
parent e63bf1b13b
commit 2253d648f1
1 changed files with 11 additions and 0 deletions
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11
include/pci.h
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@ -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))