From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Hunt, David" <david.hunt@intel.com>
Subject: Re: [PATCH v12 0/3] mempool: add external mempool manager
Date: Wed, 15 Jun 2016 12:47:15 +0100
Message-ID: <57614043.9090603@intel.com>
References: <1465919341-3209-1-git-send-email-david.hunt@intel.com>
 <1465976824-83823-1-git-send-email-david.hunt@intel.com>
 <20160615121358.5ef9f142@pcviktorin.fit.vutbr.cz>
Mime-Version: 1.0
Content-Type: text/plain; charset=windows-1252; format=flowed
Content-Transfer-Encoding: 7bit
Cc: dev@dpdk.org, olivier.matz@6wind.com, jerin.jacob@caviumnetworks.com,
 shreyansh.jain@nxp.com
To: Jan Viktorin <viktorin@rehivetech.com>
Return-path: <dev-bounces@dpdk.org>
Received: from mga11.intel.com (mga11.intel.com [192.55.52.93])
 by dpdk.org (Postfix) with ESMTP id D1B67C5C6
 for <dev@dpdk.org>; Wed, 15 Jun 2016 13:47:17 +0200 (CEST)
In-Reply-To: <20160615121358.5ef9f142@pcviktorin.fit.vutbr.cz>
List-Id: patches and discussions about DPDK <dev.dpdk.org>
List-Unsubscribe: <http://dpdk.org/ml/options/dev>,
 <mailto:dev-request@dpdk.org?subject=unsubscribe>
List-Archive: <http://dpdk.org/ml/archives/dev/>
List-Post: <mailto:dev@dpdk.org>
List-Help: <mailto:dev-request@dpdk.org?subject=help>
List-Subscribe: <http://dpdk.org/ml/listinfo/dev>,
 <mailto:dev-request@dpdk.org?subject=subscribe>
Errors-To: dev-bounces@dpdk.org
Sender: "dev" <dev-bounces@dpdk.org>



On 15/6/2016 11:13 AM, Jan Viktorin wrote:
> Hi,
>
> I've got one last question. Initially, I was interested in creating
> my own external memory provider based on a Linux Kernel driver.
> So, I've got an opened file descriptor that points to a device which
> can mmap a memory regions for me.
>
> ...
> int fd = open("/dev/uio0" ...);
> ...
> rte_mempool *pool = rte_mempool_create_empty(...);
> rte_mempool_set_ops_byname(pool, "uio_allocator_ops");
>
> I am not sure how to pass the file descriptor pointer. I thought it would
> be possible by the rte_mempool_alloc but it's not... Is it possible
> to solve this case?
>
> The allocator is device-specific.
>
> Regards
> Jan

This particular use case is not covered.

We did discuss this before, and an opaque pointer was proposed, but did 
not make it in.
http://article.gmane.org/gmane.comp.networking.dpdk.devel/39821
(and following emails in that thread)

So, the options for this use case are as follows:
1. Use the pool_data to pass data in to the alloc, then set the 
pool_data pointer before coming back from alloc. (It's a bit of a hack, 
but means no code change).
2. Add an extra parameter to the alloc function. The simplest way I can 
think of doing this is to
take the *opaque passed into rte_mempool_populate_phys, and pass it on 
into the alloc function.
This will have minimal impact on the public API,s as there is already an 
opaque there in the _populate_ funcs, we're just
reusing it for the alloc.

Do others think option 2 is OK to add this at this late stage? Even if 
the patch set has already been ACK'd?

Regards,
Dave.