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    SubjectRe: [PATCH 2/4] arch/arm/mach-at91/clock.c: Add missing IS_ERR test
    On 01/25/2011 08:55 AM, Julia Lawall wrote:
    > Function clk_get, defined just below this code, returns ERR_PTR not NULL in
    > an error case.
    >
    > The semantic match that finds this problem is as follows:
    > (http://coccinelle.lip6.fr/)
    >
    > // <smpl>
    > @r@
    > identifier f;
    > @@
    > f(...) { ... return ERR_PTR(...); }
    >
    > @@
    > identifier r.f, fld;
    > expression x;
    > statement S1,S2;
    > @@
    > x = f(...)
    > ... when != IS_ERR(x)
    > (
    > if (IS_ERR(x) ||...) S1 else S2
    > |
    > *x->fld
    > )
    > // </smpl>

    I'm always really impressed by this tool :-).

    >
    > Signed-off-by: Julia Lawall <julia@diku.dk>
    >
    > ---
    > arch/arm/mach-at91/clock.c | 2 +-
    > 1 file changed, 1 insertion(+), 1 deletion(-)
    >
    > diff --git a/arch/arm/mach-at91/clock.c b/arch/arm/mach-at91/clock.c
    > index 9113da6..c9ee6d0 100644
    > --- a/arch/arm/mach-at91/clock.c
    > +++ b/arch/arm/mach-at91/clock.c
    > @@ -224,7 +224,7 @@ void __init at91_clock_associate(const char *id, struct device *dev, const char
    > {
    > struct clk *clk = clk_get(NULL, id);
    >
    > - if (!dev || !clk || !IS_ERR(clk_get(dev, func)))
    > + if (!dev || IS_ERR(clk) || !IS_ERR(clk_get(dev, func)))
    > return;

    I think we want:

    if (!dev || !clk || IS_ERR(clk) || !IS_ERR(clk_get(dev, func)))
    return;

    Since it is valid to return a NULL clk, and we don't want to try and
    dereference it if that is the case.

    We could also probably drop the !IS_ERR(clk_get(dev, func)) check, since
    as far as I can tell it is just checking to see if the clock is already
    associated, but there is no harm in re-assigning the same values, and
    the two assignments in at91_clock_associate are going to be much quicker
    than the lookup in clk_get.

    ~Ryan

    --
    Bluewater Systems Ltd - ARM Technology Solution Centre

    Ryan Mallon 5 Amuri Park, 404 Barbadoes St
    ryan@bluewatersys.com PO Box 13 889, Christchurch 8013
    http://www.bluewatersys.com New Zealand
    Phone: +64 3 3779127 Freecall: Australia 1800 148 751
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