linux-kernel - Re: [PATCH] powerpc/powernv: use appropiate error code

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Date:   Fri, 1 Sep 2023 23:33:06 +0530
From:   Immad Mir <mirimmad@...look.com>
To:     Christophe Leroy <christophe.leroy@...roup.eu>
Cc:     "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        Immad Mir <mirimmad17@...il.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Nicholas Piggin <npiggin@...il.com>,
        "open list:LINUX FOR POWERPC (32-BIT AND 64-BIT)" 
        <linuxppc-dev@...ts.ozlabs.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] powerpc/powernv: use appropiate error code


On 01/09/23 11:10 pm, Christophe Leroy wrote:
>
> Le 01/09/2023 à 19:19, mirimmad@...look.com a écrit :
>> [Vous ne recevez pas souvent de courriers de mirimmad@...look.com. Découvrez pourquoi ceci est important à https://aka.ms/LearnAboutSenderIdentification ]
>>
>> From: Immad Mir <mirimmad17@...il.com>
>>
>> -1 is not a valid error code. This patch replaces it with -EPERM.
> Can you explain how it will work ?
> In scom_debug_init() rc is built by oring the value returned by
> scom_debug_init_one().
> What will be the result when oring some valid values with -EPERM ?
> It was working well with -1 because when you or -1 with anything you get
> -1 as result. But with your change I don't think it will work.


if EPERM is not always necessarily equal to 1, we can put a check in 
scom_debug_init before returning rc. If it is less than 1 (because AFAIK 
or-ring with negative number results back into the same negative number) 
we set rc equal to -1.

Immad.

>
> Christophe
>
>> Signed-off-by: Immad Mir <mirimmad17@...il.com>
>> ---
>>    arch/powerpc/platforms/powernv/opal-xscom.c | 4 ++--
>>    1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/powerpc/platforms/powernv/opal-xscom.c b/arch/powerpc/platforms/powernv/opal-xscom.c
>> index 262cd6fac..ce4b089dd 100644
>> --- a/arch/powerpc/platforms/powernv/opal-xscom.c
>> +++ b/arch/powerpc/platforms/powernv/opal-xscom.c
>> @@ -171,7 +171,7 @@ static int scom_debug_init_one(struct dentry *root, struct device_node *dn,
>>           if (IS_ERR(dir)) {
>>                   kfree(ent->path.data);
>>                   kfree(ent);
>> -               return -1;
>> +               return -EPERM;
>>           }
>>
>>           debugfs_create_blob("devspec", 0400, dir, &ent->path);
>> @@ -191,7 +191,7 @@ static int scom_debug_init(void)
>>
>>           root = debugfs_create_dir("scom", arch_debugfs_dir);
>>           if (IS_ERR(root))
>> -               return -1;
>> +               return -EPERM;
>>
>>           rc = 0;
>>           for_each_node_with_property(dn, "scom-controller") {
>> --
>> 2.40.0
>>