Re: [PATCH 1/1] powerpc: fix fdt_fixup_liodn_tbl_fman()

["Marek Behún" <kabel@kernel.org>]

On Wed, 12 Oct 2022 19:13:11 +0200
Heinrich Schuchardt <heinrich.schuchardt@canonical.com> wrote:

> Builiding with GCC 12.2 fails:
> 
>     arch/powerpc/cpu/mpc85xx/liodn.c: In function 'fdt_fixup_liodn_tbl_fman':
>     arch/powerpc/cpu/mpc85xx/liodn.c:340:35: error: the comparison will
>     always evaluate as 'false' for the address of 'compat'
>     will never be NULL [-Werror=address]
>       340 |                 if (tbl[i].compat == NULL)
>           |
> 
> Remove the superfluous check.
> 
> Fixes: 97a8d010e029 ("net/fman: Support both new and legacy FMan Compatibles")
> Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
> ---
>  arch/powerpc/cpu/mpc85xx/liodn.c | 3 ---
>  1 file changed, 3 deletions(-)
> 
> diff --git a/arch/powerpc/cpu/mpc85xx/liodn.c b/arch/powerpc/cpu/mpc85xx/liodn.c
> index a084002494..2d55916841 100644
> --- a/arch/powerpc/cpu/mpc85xx/liodn.c
> +++ b/arch/powerpc/cpu/mpc85xx/liodn.c
> @@ -337,9 +337,6 @@ static void fdt_fixup_liodn_tbl_fman(void *blob,
>  	for (i = 0; i < sz; i++) {
>  		int off;
>  
> -		if (tbl[i].compat == NULL)
> -			continue;
> -
>  		/* Try the new compatible first.
>  		 * If the node is missing, try the old.
>  		 */

This is the wrong fix, IMO. Instead we should do something like

diff --git a/arch/powerpc/cpu/mpc85xx/liodn.c b/arch/powerpc/cpu/mpc85xx/liodn.c
index a084002494..41b7d53ec3 100644
--- a/arch/powerpc/cpu/mpc85xx/liodn.c
+++ b/arch/powerpc/cpu/mpc85xx/liodn.c
@@ -337,7 +337,7 @@ static void fdt_fixup_liodn_tbl_fman(void *blob,
 	for (i = 0; i < sz; i++) {
 		int off;
 
-		if (tbl[i].compat == NULL)
+		if (tbl[i].compat[0] == NULL)
 			continue;
 
 		/* Try the new compatible first.
@@ -345,7 +345,7 @@ static void fdt_fixup_liodn_tbl_fman(void *blob,
 		  */
 		off = fdt_node_offset_by_compat_reg(blob,
 				tbl[i].compat[0], tbl[i].compat_offset);
-		if (off < 0)
+		if (off < 0 && tbl[i].compat[1] != NULL)
 			off = fdt_node_offset_by_compat_reg(blob,
 					tbl[i].compat[1], tbl[i].compat_offset);