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Subject: Re: [PATCH v4 03/19] powerpc: Mark variable `l` as unused, remove
 `path`
To:     Mathieu Malaterre <malat@debian.org>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
        Paul Mackerras <paulus@samba.org>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Michael Ellerman <mpe@ellerman.id.au>
References: <20180322202007.23088-4-malat@debian.org>
 <20180405202648.2836-1-malat@debian.org>
 <20180406173335.Horde.Qgml03BtHOxSl6SzIPgQLA9@messagerie.si.c-s.fr>
 <CA+7wUswhZHNabB6kAcX8Cu8zMai15RzGn9euwdKau8kY48i-CA@mail.gmail.com>
From:   christophe leroy <christophe.leroy@c-s.fr>
Message-ID: <ff779a22-0bbb-4885-5678-1371d749bc88@c-s.fr>
Date:   Tue, 24 Apr 2018 21:20:29 +0200
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Le 06/04/2018 à 20:32, Mathieu Malaterre a écrit :
> On Fri, Apr 6, 2018 at 5:33 PM, LEROY Christophe
> <christophe.leroy@c-s.fr> wrote:
>> Mathieu Malaterre <malat@debian.org> a écrit :
>>
>>> Add gcc attribute unused for `l` variable, replace `path` variable
>>> directly
>>> with prom_scratch. Fix warnings treated as errors with W=1:
>>>
>>>    arch/powerpc/kernel/prom_init.c:607:6: error: variable ‘l’ set but not
>>> used [-Werror=unused-but-set-variable]
>>>    arch/powerpc/kernel/prom_init.c:1388:8: error: variable ‘path’ set but
>>> not used [-Werror=unused-but-set-variable]
>>>
>>> Suggested-by: Michael Ellerman <mpe@ellerman.id.au>
>>> Signed-off-by: Mathieu Malaterre <malat@debian.org>
>>> ---
>>> v4: redo v3 since path variable can be avoided
>>> v3: really move path within ifdef DEBUG_PROM
>>> v2: move path within ifdef DEBUG_PROM
>>>
>>>   arch/powerpc/kernel/prom_init.c | 11 +++++------
>>>   1 file changed, 5 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/arch/powerpc/kernel/prom_init.c
>>> b/arch/powerpc/kernel/prom_init.c
>>> index f8a9a50ff9b5..4b223a9470be 100644
>>> --- a/arch/powerpc/kernel/prom_init.c
>>> +++ b/arch/powerpc/kernel/prom_init.c
>>> @@ -604,7 +604,7 @@ static void __init early_cmdline_parse(void)
>>>          const char *opt;
>>>
>>>          char *p;
>>> -       int l = 0;
>>> +       int l __maybe_unused = 0;
>>
>>
>> Instead of hiding the problem with __maybe_unused, I think we could replace
>> the
>> #ifdef CONFIG_CMDLINE
>> by a
>> if (IS_ENABLED(CONFIG_CMDLINE_BOOL))
>>
>> This is recommanded by Linux codying style
> 
> Neat. I was not aware of this trick. Does not work in this case though:
> 
> diff --git a/arch/powerpc/kernel/prom_init.c b/arch/powerpc/kernel/prom_init.c
> index 7925f64fefde..19634739b279 100644
> --- a/arch/powerpc/kernel/prom_init.c
> +++ b/arch/powerpc/kernel/prom_init.c
> @@ -604,17 +604,16 @@ static void __init early_cmdline_parse(void)
>          const char *opt;
> 
>          char *p;
> -       int l __maybe_unused = 0;
> +       int l = 0;
> 
>          prom_cmd_line[0] = 0;
>          p = prom_cmd_line;
>          if ((long)prom.chosen > 0)
>                  l = prom_getprop(prom.chosen, "bootargs", p,
> COMMAND_LINE_SIZE-1);
> -#ifdef CONFIG_CMDLINE
> -       if (l <= 0 || p[0] == '\0') /* dbl check */
> -               strlcpy(prom_cmd_line,
> -                       CONFIG_CMDLINE, sizeof(prom_cmd_line));
> -#endif /* CONFIG_CMDLINE */
> +       if (IS_ENABLED(CONFIG_CMDLINE_BOOL))
> +               if (l <= 0 || p[0] == '\0') /* dbl check */
> +                       strlcpy(prom_cmd_line,
> +                               CONFIG_CMDLINE, sizeof(prom_cmd_line));
>          prom_printf("command line: %s\n", prom_cmd_line);
> 
>   #ifdef CONFIG_PPC64
> 
> 
> leads to:
> 
>    CC      arch/powerpc/kernel/prom_init.o
> ../arch/powerpc/kernel/prom_init.c: In function ‘early_cmdline_parse’:
> ../arch/powerpc/kernel/prom_init.c:616:5: error: ‘CONFIG_CMDLINE’
> undeclared (first use in this function)
>       CONFIG_CMDLINE, sizeof(prom_cmd_line));
>       ^~~~~~~~~~~~~~
> ../arch/powerpc/kernel/prom_init.c:616:5: note: each undeclared
> identifier is reported only once for each function it appears in
> ../scripts/Makefile.build:312: recipe for target
> 'arch/powerpc/kernel/prom_init.o' failed
> make[6]: *** [arch/powerpc/kernel/prom_init.o] Error 1

And what about something like :


+       if (l <= 0 || p[0] == '\0') { /* dbl check */
  #ifdef CONFIG_CMDLINE
-       if (l <= 0 || p[0] == '\0') /* dbl check */
                 strlcpy(prom_cmd_line,
                         CONFIG_CMDLINE, sizeof(prom_cmd_line));
  #endif /* CONFIG_CMDLINE */
+}
          prom_printf("command line: %s\n", prom_cmd_line);

Christophe


> 
> 
>> Christophe
>>
>>
>>>
>>>          prom_cmd_line[0] = 0;
>>>          p = prom_cmd_line;
>>> @@ -1386,7 +1386,7 @@ static void __init reserve_mem(u64 base, u64 size)
>>>   static void __init prom_init_mem(void)
>>>   {
>>>          phandle node;
>>> -       char *path, type[64];
>>> +       char type[64];
>>>          unsigned int plen;
>>>          cell_t *p, *endp;
>>>          __be32 val;
>>> @@ -1407,7 +1407,6 @@ static void __init prom_init_mem(void)
>>>          prom_debug("root_size_cells: %x\n", rsc);
>>>
>>>          prom_debug("scanning memory:\n");
>>> -       path = prom_scratch;
>>>
>>>          for (node = 0; prom_next_node(&node); ) {
>>>                  type[0] = 0;
>>> @@ -1432,9 +1431,9 @@ static void __init prom_init_mem(void)
>>>                  endp = p + (plen / sizeof(cell_t));
>>>
>>>   #ifdef DEBUG_PROM
>>> -               memset(path, 0, PROM_SCRATCH_SIZE);
>>> -               call_prom("package-to-path", 3, 1, node, path,
>>> PROM_SCRATCH_SIZE-1);
>>> -               prom_debug("  node %s :\n", path);
>>> +               memset(prom_scratch, 0, PROM_SCRATCH_SIZE);
>>> +               call_prom("package-to-path", 3, 1, node, prom_scratch,
>>> PROM_SCRATCH_SIZE - 1);
>>> +               prom_debug("  node %s :\n", prom_scratch);
>>>   #endif /* DEBUG_PROM */
>>>
>>>                  while ((endp - p) >= (rac + rsc)) {
>>> --
>>> 2.11.0
>>
>>
>>

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