netdev - Re: [PATCH net-next] net: page pool: allow to pass zero flags to page_pool

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Date:   Wed, 25 Mar 2020 22:16:52 +0300
From:   Denis Kirjanov <kda@...ux-powerpc.org>
To:     Jesper Dangaard Brouer <brouer@...hat.com>
Cc:     netdev@...r.kernel.org, hawk@...nel.org,
        ilias.apalodimas@...aro.org
Subject: Re: [PATCH net-next] net: page pool: allow to pass zero flags to page_pool_init()

On 3/25/20, Jesper Dangaard Brouer <brouer@...hat.com> wrote:
> On Wed, 25 Mar 2020 17:12:55 +0300
> Denis Kirjanov <kda@...ux-powerpc.org> wrote:
>
>> page pool API can be useful for non-DMA cases like
>> xen-netfront driver so let's allow to pass zero flags to
>> page pool flags.
>>
>> Signed-off-by: Denis Kirjanov <kda@...ux-powerpc.org>
>> ---
>>  net/core/page_pool.c | 36 +++++++++++++++++++-----------------
>>  1 file changed, 19 insertions(+), 17 deletions(-)
>
> The pool->p.dma_dir is only used when flag PP_FLAG_DMA_MAP is used, so
> it looks more simple to do:

Yeap, agreed. Thanks!

>
> $ git diff
> diff --git a/net/core/page_pool.c b/net/core/page_pool.c
> index 626db912fce4..ef98372facf6 100644
> --- a/net/core/page_pool.c
> +++ b/net/core/page_pool.c
> @@ -43,9 +43,11 @@ static int page_pool_init(struct page_pool *pool,
>          * DMA_BIDIRECTIONAL is for allowing page used for DMA sending,
>          * which is the XDP_TX use-case.
>          */
> -       if ((pool->p.dma_dir != DMA_FROM_DEVICE) &&
> -           (pool->p.dma_dir != DMA_BIDIRECTIONAL))
> -               return -EINVAL;
> +       if (pool->p.flags & PP_FLAG_DMA_MAP) {
> +               if ((pool->p.dma_dir != DMA_FROM_DEVICE) &&
> +                   (pool->p.dma_dir != DMA_BIDIRECTIONAL))
> +                       return -EINVAL;
> +       }
>
>
>
>> diff --git a/net/core/page_pool.c b/net/core/page_pool.c
>> index 10d2b25..eeeb0d9 100644
>> --- a/net/core/page_pool.c
>> +++ b/net/core/page_pool.c
>> @@ -39,27 +39,29 @@ static int page_pool_init(struct page_pool *pool,
>>  	if (ring_qsize > 32768)
>>  		return -E2BIG;
>>
>> -	/* DMA direction is either DMA_FROM_DEVICE or DMA_BIDIRECTIONAL.
>> -	 * DMA_BIDIRECTIONAL is for allowing page used for DMA sending,
>> -	 * which is the XDP_TX use-case.
>> -	 */
>> -	if ((pool->p.dma_dir != DMA_FROM_DEVICE) &&
>> -	    (pool->p.dma_dir != DMA_BIDIRECTIONAL))
>> -		return -EINVAL;
>> -
>> -	if (pool->p.flags & PP_FLAG_DMA_SYNC_DEV) {
>> -		/* In order to request DMA-sync-for-device the page
>> -		 * needs to be mapped
>> +	if (pool->p.flags) {
>> +		/* DMA direction is either DMA_FROM_DEVICE or DMA_BIDIRECTIONAL.
>> +		 * DMA_BIDIRECTIONAL is for allowing page used for DMA sending,
>> +		 * which is the XDP_TX use-case.
>>  		 */
>> -		if (!(pool->p.flags & PP_FLAG_DMA_MAP))
>> +		if ((pool->p.dma_dir != DMA_FROM_DEVICE) &&
>> +		    (pool->p.dma_dir != DMA_BIDIRECTIONAL))
>>  			return -EINVAL;
>>
>> -		if (!pool->p.max_len)
>> -			return -EINVAL;
>> +		if (pool->p.flags & PP_FLAG_DMA_SYNC_DEV) {
>> +			/* In order to request DMA-sync-for-device the page
>> +			 * needs to be mapped
>> +			 */
>> +			if (!(pool->p.flags & PP_FLAG_DMA_MAP))
>> +				return -EINVAL;
>>
>> -		/* pool->p.offset has to be set according to the address
>> -		 * offset used by the DMA engine to start copying rx data
>> -		 */
>> +			if (!pool->p.max_len)
>> +				return -EINVAL;
>> +
>> +			/* pool->p.offset has to be set according to the address
>> +			 * offset used by the DMA engine to start copying rx data
>> +			 */
>> +		}
>>  	}
>>
>>  	if (ptr_ring_init(&pool->ring, ring_qsize, GFP_KERNEL) < 0)
>
>
>
> --
> Best regards,
>   Jesper Dangaard Brouer
>   MSc.CS, Principal Kernel Engineer at Red Hat
>   LinkedIn: http://www.linkedin.com/in/brouer
>
>