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    SubjectRe: [PATCH] Fix pointer cast for 32 bits arch
    From
    On Sun, Apr 12, 2015 at 5:38 PM, Geert Uytterhoeven
    <geert@linux-m68k.org> wrote:
    > On Sun, Apr 12, 2015 at 3:48 PM, Peter Senna Tschudin
    > <peter.senna@gmail.com> wrote:
    >> On Sun, Apr 12, 2015 at 3:05 PM, Geert Uytterhoeven
    >> <geert@linux-m68k.org> wrote:
    >>> On Sun, Apr 12, 2015 at 11:26 AM, Peter Senna Tschudin
    >>> <peter.senna@gmail.com> wrote:
    >>>> Sparse compalins about casting void * to u64 on i386.
    >>>> Change the cast to resource_size_t.
    >>>>
    >>>> Signed-off-by: Peter Senna Tschudin <peter.senna@gmail.com>
    >>>> ---
    >>>>
    >>>> Tested by compilation only. Tested for x86 and x86_64.
    >>>>
    >>>> drivers/staging/goldfish/goldfish_nand.c | 3 ++-
    >>>> include/linux/goldfish.h | 2 +-
    >>>> 2 files changed, 3 insertions(+), 2 deletions(-)
    >>>>
    >>>> diff --git a/drivers/staging/goldfish/goldfish_nand.c b/drivers/staging/goldfish/goldfish_nand.c
    >>>> index d68f216..738fdc4 100644
    >>>> --- a/drivers/staging/goldfish/goldfish_nand.c
    >>>> +++ b/drivers/staging/goldfish/goldfish_nand.c
    >>>> @@ -87,7 +87,8 @@ static u32 goldfish_nand_cmd(struct mtd_info *mtd, enum nand_cmd cmd,
    >>>> writel((u32)(addr >> 32), base + NAND_ADDR_HIGH);
    >>>> writel((u32)addr, base + NAND_ADDR_LOW);
    >>>> writel(len, base + NAND_TRANSFER_SIZE);
    >>>> - gf_write64((u64)ptr, base + NAND_DATA, base + NAND_DATA_HIGH);
    >>>> + gf_write64((resource_size_t)ptr, base + NAND_DATA,
    >>>> + base + NAND_DATA_HIGH);
    >>>
    >>> I guess sparse still complains if CONFIG_X86_PAE=y, which makes
    >>> resource_size_t u64?
    >>
    >> Yes, when CONFIG_X86_PAE=y the patch doesn't fix the warning(gcc
    >> warning). What is the correct/portable way of fixing this?
    >
    > As gf_write64() takes "unsigned long data" for its first argument, why not
    > simply cast ptr to "unsigned long"? "void *" and "unsigned long" have the same
    > size on all Linux platforms.
    >
    > Seems like there a several silly casting tricks being done in the goldfish
    > drivers:
    >
    > $ git grep -w gf_write64drivers/platform/goldfish/goldfish_pipe.c:
    > gf_write64((u64)(unsigned long)p
    > drivers/platform/goldfish/goldfish_pipe.c: gf_write64((u64)(unsigned long)p
    > drivers/platform/goldfish/goldfish_pipe.c: gf_write64((u64)
    > drivers/platform/goldfish/goldfish_pipe.c: gf_write64(addre
    > drivers/staging/goldfish/goldfish_audio.c: (gf_write64((u64)(x), data->reg_
    > drivers/staging/goldfish/goldfish_nand.c: gf_write64((u64)ptr, bas
    > drivers/tty/goldfish.c: gf_write64((u64)buf, base + GOLDFISH_TTY_DATA_PTR,
    > drivers/tty/goldfish.c: gf_write64((u64)buf, base + GOLDFISH_TTY_DATA_PTR,
    > include/linux/goldfish.h:static inline void gf_write64(unsigned long data,
    >
    > with interesting history showing one wrong cast being "fixed" using another
    > wrong cast:
    >
    > commit f4e131dc38d34469b9fee1840ad237324831bce3
    > Author: Octavian Purdila <octavian.purdila@intel.com>
    > Date: Fri May 16 08:24:59 2014 +0300
    >
    > goldfish: pipe: fix warnings for 32bit builds
    >
    > - gf_write64((u64)pipe, dev->base + PIPE_REG_CHANNEL,
    > + gf_write64((u64)(unsigned long)pipe, dev->base + PIPE_REG_CHANNEL,
    >
    > As in general casts don't belong in drivers[*], what about creating an inline
    > helper gf_set_pipe() that converts the pointer to unsigned long and calls
    > gf_write64()?
    >
    > Perhaps checkpatch should complain about casts outside header files?
    Cocinelle found 664 double casts:
    http://pastebin.com/2bi9Dg7k

    and 9 triple casts:
    http://pastebin.com/RkJhPTTV

    Those are 'not' patches, just the output of Coccinelle for analysis.
    The .cocci for triple cast:
    @@
    expression e1, e2;
    type t1, t2, t3;
    @@
    e1 =
    - (t1)(t2)(t3)
    e2

    So if there are cast patterns known to be wrong, it is easy to find
    and probably fix them with Coccinelle.


    >
    > Gr{oetje,eeting}s,
    >
    > Geert
    >
    > --
    > Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
    >
    > In personal conversations with technical people, I call myself a hacker. But
    > when I'm talking to journalists I just say "programmer" or something like that.
    > -- Linus Torvalds



    --
    Peter


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