> diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c
> index f277d023ebcd..eafeb8bf4fe4 100644
> --- a/fs/kernfs/file.c
> +++ b/fs/kernfs/file.c
> @@ -121,10 +121,10 @@ static void *kernfs_seq_start(struct seq_file *sf,
> loff_t *ppos)
> return next;
> } else {
> /*
> - * The same behavior and code as single_open(). Returns
> - * !NULL if pos is at the beginning; otherwise, NULL.
> + * The same behavior and code as single_open(). Continues
> + * if pos is at the beginning; otherwise, EOF.
> */
> - return NULL + !*ppos;
> + return *ppos ? SEQ_OPEN_SINGLE : SEQ_OPEN_EOF;
Why the somewhat obsfucating unary expression instead of a good
old if?
e.g.
return next;
}
if (*ppos)
retun SEQ_OPEN_SINGLE;
return NULL;
> ++*ppos;
> - return NULL;
> + return SEQ_OPEN_EOF;
I don't think SEQ_OPEN_EOF is all that useful. NULL is the documented
end case already.
> diff --git a/include/linux/seq_file.h b/include/linux/seq_file.h
> index 813614d4b71f..26f0758b6551 100644
> --- a/include/linux/seq_file.h
> +++ b/include/linux/seq_file.h
> @@ -37,6 +37,9 @@ struct seq_operations {
>
> #define SEQ_SKIP 1
>
> +#define SEQ_OPEN_EOF (void *)0
> +#define SEQ_OPEN_SINGLE (void *)1
I think SEQ_OPEN_SINGLE also wants a comment documenting it.
AFAICS the reason for it is that ->start needs to return something
non-NULL for the seq_file code to make progress, and there is nothing
better for the single_open case.
