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    SubjectRe: [PATCH][RFC] vsprintf: unify the format decoding layer for its 3 users
    On Fri, 27 Feb 2009 08:12:13 +0100 Frederic Weisbecker <> wrote:

    > > Why does the current ftrace_bprintk() need to hack around in (or
    > > duplicate) vprintk() internals? It's a bit grubby, but by placing an
    > > upper bound on the number of args, it could simply call vscnprintf()
    > > directly?
    > >
    > The problem is more in the way to save the parameters.
    > You have two functions:
    > _int vbin_printf(u32 *bin_buf, size_t size, const char *fmt, va_list args)
    > This one creates a compact binary packet of all args described in the format.
    > The result is a binary set of random values on bin_buf.
    > _int bstr_printf(char *buf, size_t size, const char *fmt, const u32 *bin_buf)
    > This one lately parses the buffer filled by vbin_printf() and eventually format
    > this binary contiguous set of binary values according to the format in fmt (which is the
    > same that was passed to vbin_printf()
    > The result is formatted in buf.
    > vbin uses too much specific write-to-bin_buf operations to allow us to wrap
    > vsnprintf()

    I don't know what vbin is.

    On little-endian architecture you could do something like

    u32 *p = bin_buf;
    char *fmt;
    u32 a0, a1, a2, a3, a4;

    #ifdef CONFIG_32BIT
    fmt = (char *)(*bin_buf++);
    <exercise for the reader>

    a0 = *bin_buf++;
    a1 = *bin_buf++;
    a2 = *bin_buf++;
    a3 = *bin_buf++;
    a4 = *bin_buf++;

    snprintf(somewhere, some_size, fmt, a0, a1, a2, a3, a4, a5);

    (as I said, ugly).

    but that won't work for 64-bit values on big-endian architectures. And
    it's hacky (and might not even work) for 64-bit on little endian.

    Perhaps this is the secret problem which you haven't described yet?

     \ /
      Last update: 2009-02-27 08:43    [W:0.022 / U:21.480 seconds]
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