Re: [Xen-devel] [PATCH 1 of 5] rombios/keyboard: Don't needlessly poll the status register

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Mon, 2012-11-26 at 16:41 +0000, Andrew Cooper wrote:
> Repeated polling of the status register is not going to change its value,

but the passage of time while doing multiple polls might? If this is not
the case then something needs to be said about why not.

>  so
> don't needlessly take 8192 traps to Qemu when 1 will do.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> 
> diff -r 0049de3827bc -r 1728fb789940 tools/firmware/rombios/rombios.c
> --- a/tools/firmware/rombios/rombios.c
> +++ b/tools/firmware/rombios/rombios.c
> @@ -1805,12 +1805,12 @@ keyboard_init()
>      while ( (inb(0x64) & 0x02) && (--max>0)) outb(0x80, 0x00);
>  
>      /* flush incoming keys */
> -    max=0x2000;
> +    max=2;
>      while (--max > 0) {
>          outb(0x80, 0x00);
>          if (inb(0x64) & 0x01) {
>              inb(0x60);
> -            max = 0x2000;
> +            max = 2;
>              }
>          }
>  
> 
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