linux-kernel - Re: [PATCH] lightnvm: pass dma address to hardware rather than pointer

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Message-ID: <5728E2E0.1000106@bjorling.me>
Date:	Tue, 3 May 2016 19:41:52 +0200
From:	Matias Bjørling <m@...rling.me>
To:	Arnd Bergmann <arnd@...db.de>, Keith Busch <keith.busch@...el.com>,
	Jens Axboe <axboe@...com>
Cc:	Javier González <javier@...xlabs.com>,
	linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] lightnvm: pass dma address to hardware rather than
 pointer

On 05/03/2016 05:22 PM, Arnd Bergmann wrote:
> A recent change to lightnvm added code to pass a kernel pointer
> to the hardware, which gcc complained about:
>
> drivers/nvme/host/lightnvm.c: In function 'nvme_nvm_rqtocmd':
> drivers/nvme/host/lightnvm.c:472:32: error: cast from pointer to integer of different size [-Werror=pointer-to-int-cast]
>    c->ph_rw.metadata = cpu_to_le64(rqd->meta_list);
>
> It looks like this has no way of working anyway, so this changes
> the code to pass the dma_address instead. This was most likely
> what was intended here. Neither of the two are currently ever
> written to, so the effect is the same for now.
>
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> Fixes: a34b1eb78e21 ("lightnvm: enable metadata to be sent to device")
> ---
>   drivers/nvme/host/lightnvm.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/nvme/host/lightnvm.c b/drivers/nvme/host/lightnvm.c
> index fadeb54bc7df..65de1e56e59a 100644
> --- a/drivers/nvme/host/lightnvm.c
> +++ b/drivers/nvme/host/lightnvm.c
> @@ -469,7 +469,7 @@ static inline void nvme_nvm_rqtocmd(struct request *rq, struct nvm_rq *rqd,
>   	c->ph_rw.opcode = rqd->opcode;
>   	c->ph_rw.nsid = cpu_to_le32(ns->ns_id);
>   	c->ph_rw.spba = cpu_to_le64(rqd->ppa_addr.ppa);
> -	c->ph_rw.metadata = cpu_to_le64(rqd->meta_list);
> +	c->ph_rw.metadata = cpu_to_le64(rqd->dma_meta_list);
>   	c->ph_rw.control = cpu_to_le16(rqd->flags);
>   	c->ph_rw.length = cpu_to_le16(rqd->nr_pages - 1);
>
>

Thanks Arnd, good catch. I haven't sent the 4.7 patches upstream yet. Do 
you want me to squash your patch into Javier's or keep it separately?