[PATCH] Fix pointer cast for 32 bits arch

[Peter Senna Tschudin]

On Sun, Apr 12, 2015 at 5:38 PM, Geert Uytterhoeven
<geert at linux-m68k.org> wrote:
> On Sun, Apr 12, 2015 at 3:48 PM, Peter Senna Tschudin
> <peter.senna at gmail.com> wrote:
>> On Sun, Apr 12, 2015 at 3:05 PM, Geert Uytterhoeven
>> <geert at linux-m68k.org> wrote:
>>> On Sun, Apr 12, 2015 at 11:26 AM, Peter Senna Tschudin
>>> <peter.senna at 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 at 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 at 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 at 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