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Re: [Xen-devel] [PATCH] [1/4] put xen console message into syslog butxm

On 11 Jul 2006, at 09:34, MINAI Katsuhito wrote:

Please let me confirm the following for my understanding.

- Xen should return the index of the oldest character on the console
  ring when the index that the caller specified is older than
  the range of the console ring.

Yes, that is an out-of-range input index gets 'rounded up' to the first in-range index. I think that seems a sensible method for bootstrapping a caller with no knowledge about current ring indexes -- they'd pass zero as input and then get back information about the first valid index. Another way would be to have an input flag or unique input index value that means 'just get me characters from the first valid index'. I somewhat prefer the method I already described though.

- I think that Xen would return index position of "last" byte
  returned, not first byte.

Seems less natural to me, but we could do it either way. Clearly first can be computed from last, and vice versa.

Also, keeping the facility to clear the console buffer seems sensible (so that 'xm dmesg' can continue to support the normal Linux dmesg -c option) -- but having a separate clear_console_ring dom0_op for that would be cleaner.


 -- Keir

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