From: Dan Williams <dan.j.williams@intel.com>
To: Christoph Hellwig <hch@infradead.org>,
Vinod Koul <vinod.koul@intel.com>,
linux-renesas-soc@vger.kernel.org,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"dmaengine@vger.kernel.org" <dmaengine@vger.kernel.org>,
iommu@lists.linux-foundation.org, robin.murphy@arm.com,
Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
geert+renesas@glider.be, Linus Walleij <linus.walleij@linaro.org>,
Dan J Williams <dan.j.williams@intel.com>,
Arnd Bergmann <arnd@arndb.de>,
linux-arch@vger.kernel.org
Subject: Re: [PATCH v5 3/9] dma-mapping: add dma_{map,unmap}_resource
Date: Thu, 10 Mar 2016 22:47:10 -0800 [thread overview]
Message-ID: <CAPcyv4gO4EZnBuVKXT8+gsMhbHJzuK7sfr0uRcjVdJP-nUUz4A@mail.gmail.com> (raw)
In-Reply-To: <20160310160522.GB1111@bigcity.dyn.berto.se>
On Thu, Mar 10, 2016 at 8:05 AM, Niklas S??derlund
<niklas.soderlund@ragnatech.se> wrote:
> Hi Christoph,
>
> On 2016-03-07 23:38:47 -0800, Christoph Hellwig wrote:
>> Please add some documentation on where/how this should be used. It's
>> not a very obvious interface.
>
> Good idea, I have added the following to Documentation/DMA-API.txt and
> folded it in to this patch. Do you feel it's adequate and do you know
> anywhere else I should add documentation?
>
> diff --git a/Documentation/DMA-API.txt b/Documentation/DMA-API.txt
> index 45ef3f2..248556a 100644
> --- a/Documentation/DMA-API.txt
> +++ b/Documentation/DMA-API.txt
> @@ -277,14 +277,29 @@ and <size> parameters are provided to do partial page mapping, it is
> recommended that you never use these unless you really know what the
> cache width is.
>
> +dma_addr_t
> +dma_map_resource(struct device *dev, phys_addr_t phys_addr, size_t size,
> + enum dma_data_direction dir, struct dma_attrs *attrs)
> +
> +Maps a MMIO region so it can be accessed by the device and returns the
> +DMA address of the memory. API should only be used to map device MMIO,
> +mapping of RAM is not permitted.
> +
I think it is confusing to use the dma_ prefix for this peer-to-peer
mmio functionality. dma_addr_t is a device's view of host memory.
Something like bus_addr_t bus_map_resource(). Doesn't this routine
also need the source device in addition to the target device? The
resource address is from the perspective of the host cpu, it may be a
different address space in the view of two devices relative to each
other.
next prev parent reply other threads:[~2016-03-11 6:47 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-08 2:42 [PATCH v5 0/9] dmaengine: rcar-dmac: add iommu support for slave transfers Niklas Söderlund
2016-03-08 2:42 ` Niklas Söderlund
2016-03-08 2:42 ` [PATCH v5 1/9] iommu: Add MMIO mapping type Niklas Söderlund
[not found] ` <1457404974-1800-2-git-send-email-niklas.soderlund+renesas-1zkq55x86MTxsAP9Fp7wbw@public.gmane.org>
2016-03-17 11:18 ` Laurent Pinchart
2016-03-17 11:18 ` Laurent Pinchart
2016-03-08 2:42 ` [PATCH v5 2/9] dma-mapping: add {map,unmap}_resource to dma_map_ops Niklas Söderlund
2016-03-08 2:42 ` Niklas Söderlund
[not found] ` <1457404974-1800-1-git-send-email-niklas.soderlund+renesas-1zkq55x86MTxsAP9Fp7wbw@public.gmane.org>
2016-03-08 2:42 ` [PATCH v5 3/9] dma-mapping: add dma_{map,unmap}_resource Niklas Söderlund
2016-03-08 2:42 ` Niklas Söderlund
2016-03-08 7:38 ` Christoph Hellwig
2016-03-10 16:05 ` Niklas S??derlund
2016-03-10 16:05 ` Niklas S??derlund
2016-03-11 6:19 ` Vinod Koul
2016-03-11 6:19 ` Vinod Koul
2016-03-11 6:47 ` Dan Williams [this message]
2016-03-11 6:47 ` Dan Williams
2016-03-11 11:15 ` Christoph Hellwig
2016-03-11 12:58 ` Niklas Söderlund
2016-03-11 12:58 ` Niklas Söderlund
2016-03-15 8:22 ` Christoph Hellwig
[not found] ` <20160315082254.GE9136-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
2016-03-17 11:33 ` Laurent Pinchart
2016-03-17 11:33 ` Laurent Pinchart
2016-03-21 15:26 ` Christoph Hellwig
2016-03-21 15:26 ` Christoph Hellwig
[not found] ` <20160321152601.GA11674-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
2016-04-13 13:29 ` Niklas Söderlund
2016-04-13 13:29 ` Niklas Söderlund
2016-04-21 9:48 ` Niklas Söderlund
2016-04-21 9:48 ` Niklas Söderlund
2016-04-21 13:49 ` Christoph Hellwig
2016-04-21 13:49 ` Christoph Hellwig
2016-04-25 14:26 ` Niklas Söderlund
2016-04-25 14:26 ` Niklas Söderlund
2016-04-25 19:10 ` Christoph Hellwig
2016-04-25 19:10 ` Christoph Hellwig
[not found] ` <20160425191004.GA13906-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
2016-04-26 13:29 ` Niklas Söderlund
2016-04-26 13:29 ` Niklas Söderlund
[not found] ` <CAPcyv4gO4EZnBuVKXT8+gsMhbHJzuK7sfr0uRcjVdJP-nUUz4A-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2016-03-11 13:46 ` Robin Murphy
2016-03-11 13:46 ` Robin Murphy
2016-03-11 17:51 ` Dan Williams
2016-03-08 2:42 ` [PATCH v5 4/9] arm: dma-mapping: add {map, unmap}_resource for iommu ops Niklas Söderlund
2016-03-08 2:42 ` [PATCH v5 4/9] arm: dma-mapping: add {map,unmap}_resource " Niklas Söderlund
2016-03-08 2:42 ` [PATCH v5 5/9] dmaengine: rcar-dmac: slave address are physical Niklas Söderlund
2016-03-08 2:42 ` Niklas Söderlund
[not found] ` <1457404974-1800-6-git-send-email-niklas.soderlund+renesas-1zkq55x86MTxsAP9Fp7wbw@public.gmane.org>
2016-03-17 11:30 ` Laurent Pinchart
2016-03-17 11:30 ` Laurent Pinchart
2016-03-08 2:42 ` [PATCH v5 6/9] dmaengine: rcar-dmac: group slave configuration Niklas Söderlund
2016-03-08 2:42 ` Niklas Söderlund
[not found] ` <1457404974-1800-7-git-send-email-niklas.soderlund+renesas-1zkq55x86MTxsAP9Fp7wbw@public.gmane.org>
2016-03-17 11:28 ` Laurent Pinchart
2016-03-17 11:28 ` Laurent Pinchart
2016-03-08 2:42 ` [PATCH v5 7/9] dmaengine: rcar-dmac: add iommu support for slave transfers Niklas Söderlund
2016-03-08 2:42 ` Niklas Söderlund
2016-03-08 2:42 ` [PATCH v5 8/9] ARM: dts: r8a7790: add iommus to dmac0 and dmac1 Niklas Söderlund
2016-03-08 2:42 ` Niklas Söderlund
2016-03-08 2:42 ` [PATCH v5 9/9] ARM: dts: r8a7791: " Niklas Söderlund
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