Re: [PATCH] ppc4xx: ocm: fix errnous "failed to create file" errors

[Michael Ellerman]

Hi Christian,

Christian Lamparter <chunk...@gmail.com> writes:
> Previously, the kernel would complain:
>
> | debugfs ppc4xx ocm: failed to create file
>
> But the "info" file was still created and working. This
> is because debugfs_create_file() returns a pointer to a
> struct *dentry on success or -ENODEV when debugfs isn't
> available. This patch fixes both the debugfs_create_dir()
> and debugfs_create_file() check, so this will work as
> expected.
>
> Signed-off-by: Christian Lamparter <chunk...@gmail.com>
>
> diff --git a/arch/powerpc/platforms/4xx/ocm.c 
> b/arch/powerpc/platforms/4xx/ocm.c
> index 69d9f60d9fe5..e616c8636303 100644
> --- a/arch/powerpc/platforms/4xx/ocm.c
> +++ b/arch/powerpc/platforms/4xx/ocm.c
> @@ -293,13 +293,14 @@ static int ocm_debugfs_init(void)
>  {
>       struct dentry *junk;
>  
> -     junk = debugfs_create_dir("ppc4xx_ocm", 0);
> -     if (!junk) {
> +     junk = debugfs_create_dir("ppc4xx_ocm", NULL);
> +     if (IS_ERR_OR_NULL(junk)) {
>               printk(KERN_ALERT "debugfs ppc4xx ocm: failed to create dir\n");
>               return -1;
>       }
>  
> -     if (debugfs_create_file("info", 0644, junk, NULL, &ocm_debugfs_fops)) {
> +     if (IS_ERR_OR_NULL(debugfs_create_file("info", 0644, junk, NULL,
> +                                            &ocm_debugfs_fops))) {
>               printk(KERN_ALERT "debugfs ppc4xx ocm: failed to create 
> file\n");
>               return -1;
>       }

Typically we would just make the whole function not compile when DEBUG_FS
is disabled, eg:

diff --git a/arch/powerpc/platforms/4xx/ocm.c b/arch/powerpc/platforms/4xx/ocm.c
index f5bbd4563342..c5293a28545c 100644
--- a/arch/powerpc/platforms/4xx/ocm.c
+++ b/arch/powerpc/platforms/4xx/ocm.c
@@ -286,6 +286,7 @@ static const struct file_operations ocm_debugfs_fops = {
        .release = single_release,
 };
 
+#ifdef CONFIG_DEBUG_FS
 static int ocm_debugfs_init(void)
 {
        struct dentry *junk;
@@ -303,6 +304,9 @@ static int ocm_debugfs_init(void)
 
        return 0;
 }
+#else
+static int ocm_debugfs_init(void) { return 0; }
+#endif
 
 void *ppc4xx_ocm_alloc(phys_addr_t *phys, int size, int align,
                        int flags, const char *owner)


I don't really mind, but I think the #ifdef approach is simpler to
reason about.

cheers