netdev - Re: [PATCH vringh 2/2] caif_virtio: Introduce caif over virtio

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Date:	Wed, 13 Feb 2013 13:50:41 +0100
From:	Sjur Brændeland <sjurbren@...il.com>
To:	Rusty Russell <rusty@...tcorp.com.au>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Ohad Ben-Cohen <ohad@...ery.com>,
	Vikram ARV <vikram.arv@...ricsson.com>,
	Dmitry TARNYAGIN <dmitry.tarnyagin@...ricsson.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Erwan YVIN <erwan.yvin@...ricsson.com>,
	"virtualization@...ts.linux-foundation.org" 
	<virtualization@...ts.linux-foundation.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Ido Yariv <ido@...ery.com>
Subject: Re: [PATCH vringh 2/2] caif_virtio: Introduce caif over virtio

Hi Rusty,

On Wed, Feb 13, 2013 at 11:16 AM, Rusty Russell <rusty@...tcorp.com.au> wrote:
> Sjur BRENDELAND <sjur.brandeland@...ricsson.com> writes:
>>> > +static inline void ctx_prep_iov(struct cfv_napi_context *ctx)
>>> > +{
>>> > +  if (ctx->riov.allocated) {
>>> > +          kfree(ctx->riov.iov);
>>> > +          ctx->riov.iov = NULL;
>>> > +          ctx->riov.allocated = false;
>>> > +  }
>>> > +  ctx->riov.iov = NULL;
>>> > +  ctx->riov.i = 0;
>>> > +  ctx->riov.max = 0;
>>> > +}
>>>
>>> Hmm, we should probably make sure you don't have to do this: that if
>>> allocated once, you can simply reuse it by setting i = 0.
>>
>> Yes, I had problems getting the alloc/free of iov right. This is
>> perhaps the least intuitively part of the API. I maybe it's just me, but
>> I think some more helper functions and support from vringh in this
>> area would be great.
>
> Yes, I've neatened my git tree, an in particular added a commit which
> covers this explicitly, and one for the -EPROTO when we get unexpected
> r/w bufs.  I've appended them below.

Great, thanks. This helps a lot. I picked up your patch-sett yesterday
so my V2 patch-set is using this already.
...
> +static inline void vringh_iov_init(struct vringh_iov *iov,
> +                                  struct iovec *iovec, unsigned num)
> +{
> +       iov->used = iov->i = 0;
> +       iov->off = 0;
> +       iov->max_num = num;
> +       iov->iov = iovec;
> +}

How about supporting struct vringh_kiov and struct kvec as well?
I currently get the following complaints with my V2 patch-set:

drivers/net/caif/caif_virtio.c:486:2: warning: passing argument 1 of
‘vringh_iov_init’ from incompatible pointer type [enabled by default]
...

Thanks,
Sjur
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