[PATCH] virtio: replace constant parameter '1' with num

[PATCH] virtio: replace constant parameter '1' with num

[liush]

'num' can represent the value of out_sgs(in_sags), no need to pass 
in constant parameters in 'virtqueue_add'.

Signed-off-by: liush <liush@allwinnertech.com>
---
 drivers/virtio/virtio_ring.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index becc776..7583f8b 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -1760,7 +1760,7 @@ int virtqueue_add_outbuf(struct virtqueue *vq,
 			 void *data,
 			 gfp_t gfp)
 {
-	return virtqueue_add(vq, &sg, num, 1, 0, data, NULL, gfp);
+	return virtqueue_add(vq, &sg, num, num, 0, data, NULL, gfp);
 }
 EXPORT_SYMBOL_GPL(virtqueue_add_outbuf);
 
@@ -1782,7 +1782,7 @@ int virtqueue_add_inbuf(struct virtqueue *vq,
 			void *data,
 			gfp_t gfp)
 {
-	return virtqueue_add(vq, &sg, num, 0, 1, data, NULL, gfp);
+	return virtqueue_add(vq, &sg, num, 0, num, data, NULL, gfp);
 }
 EXPORT_SYMBOL_GPL(virtqueue_add_inbuf);
 
-- 
2.7.4

Re: [PATCH] virtio: replace constant parameter '1' with num

[Michael S. Tsirkin]

On Tue, Dec 08, 2020 at 07:57:51PM +0800, liush wrote:
> 'num' can represent the value of out_sgs(in_sags), no need to pass 
> in constant parameters in 'virtqueue_add'.
> 
> Signed-off-by: liush <liush@allwinnertech.com>

Point being?
A constant is likely easier for the compiler to optimize ...

> ---
>  drivers/virtio/virtio_ring.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index becc776..7583f8b 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -1760,7 +1760,7 @@ int virtqueue_add_outbuf(struct virtqueue *vq,
>  			 void *data,
>  			 gfp_t gfp)
>  {
> -	return virtqueue_add(vq, &sg, num, 1, 0, data, NULL, gfp);
> +	return virtqueue_add(vq, &sg, num, num, 0, data, NULL, gfp);
>  }
>  EXPORT_SYMBOL_GPL(virtqueue_add_outbuf);
>  
> @@ -1782,7 +1782,7 @@ int virtqueue_add_inbuf(struct virtqueue *vq,
>  			void *data,
>  			gfp_t gfp)
>  {
> -	return virtqueue_add(vq, &sg, num, 0, 1, data, NULL, gfp);
> +	return virtqueue_add(vq, &sg, num, 0, num, data, NULL, gfp);
>  }
>  EXPORT_SYMBOL_GPL(virtqueue_add_inbuf);
>  
> -- 
> 2.7.4

回复：[PATCH] virtio: replace constant parameter '1' with num

[刘邵华BTD]

Hi Michael,
>> 'num' can represent the value of out_sgs(in_sags), no need to pass 
>> in constant parameters in 'virtqueue_add'.
>> 
>> Signed-off-by: liush <liush@allwinnertech.com>

>Point being?
>A constant is likely easier for the compiler to optimize ...

Thanks.
I was unaware that a constant was for compiler optimization. 
It seems that 'num' is more readable compared to a constant. And 'virtqueue_add_*' 
does not specify that only one buf is added, but ‘1’ is passed in ‘virtqueue_add’, 
which limits the function of 'virtqueue_add_*'. Besides compilation optimization, 
are there any other considerations.

>> ---
>>  drivers/virtio/virtio_ring.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>> 
>> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
>> index becc776..7583f8b 100644
>> --- a/drivers/virtio/virtio_ring.c
>> +++ b/drivers/virtio/virtio_ring.c
>> @@ -1760,7 +1760,7 @@ int virtqueue_add_outbuf(struct virtqueue *vq,
>>      void *data,
>>      gfp_t gfp)
>>  {
>> - return virtqueue_add(vq, &sg, num, 1, 0, data, NULL, gfp);
>> + return virtqueue_add(vq, &sg, num, num, 0, data, NULL, gfp);
>>  }
>>  EXPORT_SYMBOL_GPL(virtqueue_add_outbuf);
>>  
>> @@ -1782,7 +1782,7 @@ int virtqueue_add_inbuf(struct virtqueue *vq,
>>     void *data,
>>     gfp_t gfp)
>>  {
>> - return virtqueue_add(vq, &sg, num, 0, 1, data, NULL, gfp);
>> + return virtqueue_add(vq, &sg, num, 0, num, data, NULL, gfp);
>>  }
>>  EXPORT_SYMBOL_GPL(virtqueue_add_inbuf);
>>  
>> --