Messages in this thread Patch in this message | | | From | Andy Shevchenko <> | Subject | [PATCH v2 5/7] x86/boot: Add MMIO byte accessors | Date | Tue, 19 Mar 2019 21:43:23 +0300 |
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readb() and writeb() would help to access serial device via MMIO address space.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> --- arch/x86/boot/boot.h | 12 ++++++++++++ 1 file changed, 12 insertions(+)
diff --git a/arch/x86/boot/boot.h b/arch/x86/boot/boot.h index 86641b2e83f8..b2a272d3f36b 100644 --- a/arch/x86/boot/boot.h +++ b/arch/x86/boot/boot.h @@ -79,6 +79,18 @@ static inline void io_delay(void) asm volatile("outb %%al,%0" : : "dN" (DELAY_PORT)); } +static inline u8 readb(const volatile void __iomem *addr) +{ + u8 v; + asm volatile("movb %1,%0" : "=q" (v) : "m" (*(volatile u8 __force *)addr)); + return v; +} + +static inline void writeb(u8 v, volatile void __iomem *addr) +{ + asm volatile("movb %0,%1" : : "q" (v), "m" (*(volatile u8 __force *)addr)); +} + /* These functions are used to reference data in other segments. */ static inline u16 ds(void) -- 2.20.1
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