Re: [PATCH] sbitmap, scsi/target: add seq_file forward declaration

[Bart Van Assche]

On Fri, 2018-07-06 at 15:23 +0200, Arnd Bergmann wrote:
> The target core runs into a warning in the linux/sbitmap.h
> file in some configurations:
> 
> In file included from include/target/target_core_base.h:7,
>                  from drivers/target/target_core_fabric_lib.c:41:
> include/linux/sbitmap.h:331:46: error: 'struct seq_file' declared inside parameter list will not be visible outside of this definition or declaration [-Werror]
>  void sbitmap_show(struct sbitmap *sb, struct seq_file *m);
>                                               ^~~~~~~~
> 
> In general, headers should not depend on others being included first,
> so this fixes it with a forward declaration for that struct name, but
> we probably want to merge the patch through the scsi tree to help
> bisection.
> 
> Fixes: 10e9cbb6b531 ("scsi: target: Convert target drivers to use sbitmap")
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
> ---
>  include/linux/sbitmap.h | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/include/linux/sbitmap.h b/include/linux/sbitmap.h
> index e6539536dea9..cc54b9f7ff8b 100644
> --- a/include/linux/sbitmap.h
> +++ b/include/linux/sbitmap.h
> @@ -321,6 +321,8 @@ static inline int sbitmap_test_bit(struct sbitmap *sb, unsigned int bitnr)
>  
>  unsigned int sbitmap_weight(const struct sbitmap *sb);
>  
> +struct seq_file;
> +
>  /**
>   * sbitmap_show() - Dump &struct sbitmap information to a &struct seq_file.
>   * @sb: Bitmap to show.

In many Linux kernel header files all forward declarations are grouped near
the start of the header file (after #includes and #defines and before structure
definitions). Should we follow that pattern in <linux/sbitmap.h>?

Thanks,

Bart.