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    SubjectRe: ehci dynamic debug problem
    On Fri, Apr 13, 2012 at 11:19:37AM -0400, Alan Stern wrote:
    > On Fri, 13 Apr 2012, Johannes Stezenbach wrote:
    >
    > > On Fri, Apr 13, 2012 at 10:35:59AM -0400, Alan Stern wrote:
    > > > On Fri, 13 Apr 2012, Johannes Stezenbach wrote:
    > > > >
    > > > > Does dynamic debug offer an "is the message two lines below enabled" test?
    > > > > Simply changing the "#ifdef DEBUG" for dbg_port_buf()
    > > > > to "#if defined(DEBUG) || defined(CONFIG_DYNAMIC_DEBUG)"
    > > > > is probably not acceptable due to the overhead of dbg_port_buf()?
    > > >
    > > > I don't understand your question. Doesn't dbg_port_buf need to be
    > > > defined whenever dynamic debugging is enabled?
    > > >
    > > > Alternatively, the definition of dbg_port_buf (and related routines) in
    > > > the !defined(DEBUG) case could be changed; you could add
    > > >
    > > > buf[0] = 0;
    > > >
    > > > That way you wouldn't get garbage out, although you wouldn't get
    > > > anything useful either.
    > >
    > > The ideal solution I'm looking for gives useful output
    > > when dynamic debugging is enabled for ehci, but does no
    > > useless string formatting when CONFIG_DYNAMIC_DEBUG is y
    > > but the dynamic debug for ehci is disabled.
    >
    > But there is no such thing as dynamic debug for ehci, is there?
    > There's a separate dynamic debug setting for each dev_dbg statement.
    > So your ideal solution makes no sense.

    When CONFIG_DYNAMIC_DEBUG=y but ehci debug is disabled
    in /sys/kernel/debug/dynamic_debug/control, then
    dbg_port() calls dbg_port_buf() which would
    format the string, then calls ehci_dbg() which
    calls dev_dbg() which discards it.

    Does it make sense now?


    Thanks,
    Johannes


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