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    Subject[PATCH v3 2/4] x86: add two helper macros for fixed address mapping
    Date
    Sometimes fixmap will be used to map an physical address which
    is not PAGE align, so to use it we need first map it and then
    add the address offset to the mapped fixed address. These 2 new
    helpers are suggested by Ingo Molnar to make the process simpler.

    For a physicall address like "phys", a directly usable virtual
    address can be get by
    virt = (void *)set_fixmap_offset(fixed_idx, phys);
    or
    virt = (void *)set_fixmap_offset_nocache(fixed_idx, phys);
    (depends on whether the physical address is cachable or not).

    Signed-off-by: Feng Tang <feng.tang@intel.com>
    Cc: x86@kernel.org
    ---
    arch/x86/include/asm/fixmap.h | 15 +++++++++++++++
    1 files changed, 15 insertions(+), 0 deletions(-)
    mode change 100644 => 100755 arch/x86/include/asm/fixmap.h

    diff --git a/arch/x86/include/asm/fixmap.h b/arch/x86/include/asm/fixmap.h
    old mode 100644
    new mode 100755
    index d07b44f..4d293dc
    --- a/arch/x86/include/asm/fixmap.h
    +++ b/arch/x86/include/asm/fixmap.h
    @@ -214,5 +214,20 @@ static inline unsigned long virt_to_fix(const unsigned long vaddr)
    BUG_ON(vaddr >= FIXADDR_TOP || vaddr < FIXADDR_START);
    return __virt_to_fix(vaddr);
    }
    +
    +/* Return an pointer with offset calculated */
    +static inline unsigned long __set_fixmap_offset(enum fixed_addresses idx,
    + phys_addr_t phys, pgprot_t flags)
    +{
    + __set_fixmap(idx, phys, flags);
    + return fix_to_virt(idx) + (phys & (PAGE_SIZE - 1));
    +}
    +
    +#define set_fixmap_offset(idx, phys) \
    + __set_fixmap_offset(idx, phys, PAGE_KERNEL)
    +
    +#define set_fixmap_offset_nocache(idx, phys) \
    + __set_fixmap_offset(idx, phys, PAGE_KERNEL_NOCACHE)
    +
    #endif /* !__ASSEMBLY__ */
    #endif /* _ASM_X86_FIXMAP_H */
    --
    1.7.0.4


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