Check IS_ENABLED(CONFIG_TUN_VNET_CROSS_LE) to save some lines and make
future changes easier.

Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
---
 drivers/net/tun.c | 26 ++++++++------------------
 1 file changed, 8 insertions(+), 18 deletions(-)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index e816aaba8e5f2ed06f8832f79553b6c976e75bb8..452fc5104260fe7ff5fdd5cedc5d2647cbe35c79 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -298,10 +298,10 @@ static bool tun_napi_frags_enabled(const struct tun_file *tfile)
 	return tfile->napi_frags_enabled;
 }
 
-#ifdef CONFIG_TUN_VNET_CROSS_LE
 static inline bool tun_legacy_is_little_endian(struct tun_struct *tun)
 {
-	return tun->flags & TUN_VNET_BE ? false :
+	return !(IS_ENABLED(CONFIG_TUN_VNET_CROSS_LE) &&
+		 (tun->flags & TUN_VNET_BE)) &&
 		virtio_legacy_is_little_endian();
 }
 
@@ -309,6 +309,9 @@ static long tun_get_vnet_be(struct tun_struct *tun, int __user *argp)
 {
 	int be = !!(tun->flags & TUN_VNET_BE);
 
+	if (!IS_ENABLED(CONFIG_TUN_VNET_CROSS_LE))
+		return -EINVAL;
+
 	if (put_user(be, argp))
 		return -EFAULT;
 
@@ -319,6 +322,9 @@ static long tun_set_vnet_be(struct tun_struct *tun, int __user *argp)
 {
 	int be;
 
+	if (!IS_ENABLED(CONFIG_TUN_VNET_CROSS_LE))
+		return -EINVAL;
+
 	if (get_user(be, argp))
 		return -EFAULT;
 
@@ -329,22 +335,6 @@ static long tun_set_vnet_be(struct tun_struct *tun, int __user *argp)
 
 	return 0;
 }
-#else
-static inline bool tun_legacy_is_little_endian(struct tun_struct *tun)
-{
-	return virtio_legacy_is_little_endian();
-}
-
-static long tun_get_vnet_be(struct tun_struct *tun, int __user *argp)
-{
-	return -EINVAL;
-}
-
-static long tun_set_vnet_be(struct tun_struct *tun, int __user *argp)
-{
-	return -EINVAL;
-}
-#endif /* CONFIG_TUN_VNET_CROSS_LE */
 
 static inline bool tun_is_little_endian(struct tun_struct *tun)
 {

-- 
2.48.1

Akihiko Odaki wrote:
> Check IS_ENABLED(CONFIG_TUN_VNET_CROSS_LE) to save some lines and make
> future changes easier.
> 
> Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
> Reviewed-by: Willem de Bruijn <willemb@google.com>
> ---
>  drivers/net/tun.c | 26 ++++++++------------------
>  1 file changed, 8 insertions(+), 18 deletions(-)
> 
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index e816aaba8e5f2ed06f8832f79553b6c976e75bb8..452fc5104260fe7ff5fdd5cedc5d2647cbe35c79 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -298,10 +298,10 @@ static bool tun_napi_frags_enabled(const struct tun_file *tfile)
>  	return tfile->napi_frags_enabled;
>  }
>  
> -#ifdef CONFIG_TUN_VNET_CROSS_LE
>  static inline bool tun_legacy_is_little_endian(struct tun_struct *tun)
>  {
> -	return tun->flags & TUN_VNET_BE ? false :
> +	return !(IS_ENABLED(CONFIG_TUN_VNET_CROSS_LE) &&
> +		 (tun->flags & TUN_VNET_BE)) &&
>  		virtio_legacy_is_little_endian();

Since I have other comments to the series:

Can we make this a bit simpler to the reader, by splitting the test:

    if (IS_ENABLED(CONFIG_TUN_VNET_CROSS_LE) && tun->flags & TUN_VNET_BE)
            return false;

    return virtio_legacy_is_little_endian();

On 2025/02/06 6:06, Willem de Bruijn wrote:
> Akihiko Odaki wrote:
>> Check IS_ENABLED(CONFIG_TUN_VNET_CROSS_LE) to save some lines and make
>> future changes easier.
>>
>> Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
>> Reviewed-by: Willem de Bruijn <willemb@google.com>
>> ---
>>   drivers/net/tun.c | 26 ++++++++------------------
>>   1 file changed, 8 insertions(+), 18 deletions(-)
>>
>> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
>> index e816aaba8e5f2ed06f8832f79553b6c976e75bb8..452fc5104260fe7ff5fdd5cedc5d2647cbe35c79 100644
>> --- a/drivers/net/tun.c
>> +++ b/drivers/net/tun.c
>> @@ -298,10 +298,10 @@ static bool tun_napi_frags_enabled(const struct tun_file *tfile)
>>   	return tfile->napi_frags_enabled;
>>   }
>>   
>> -#ifdef CONFIG_TUN_VNET_CROSS_LE
>>   static inline bool tun_legacy_is_little_endian(struct tun_struct *tun)
>>   {
>> -	return tun->flags & TUN_VNET_BE ? false :
>> +	return !(IS_ENABLED(CONFIG_TUN_VNET_CROSS_LE) &&
>> +		 (tun->flags & TUN_VNET_BE)) &&
>>   		virtio_legacy_is_little_endian();
> 
> Since I have other comments to the series:
> 
> Can we make this a bit simpler to the reader, by splitting the test:
> 
>      if (IS_ENABLED(CONFIG_TUN_VNET_CROSS_LE) && tun->flags & TUN_VNET_BE)
>              return false;
> 
>      return virtio_legacy_is_little_endian();
> 

I kept all in one expression to show how different variables are reduced 
into one bool value, but I agree it is too complicated.

I'm adding a new variable to simplify this. The return statement will 
look like: return !be && virtio_legacy_is_little_endian();

It means: for tun, whether the legacy format is in little endian will be 
determined from the tun-specific big-endian flag and the virtio's common 
logic.