From: Stephen Warren <swarren@wwwdotorg.org>
To: Richard Zhao <rizhao@nvidia.com>
Cc: linux-kernel@vger.kernel.org, linux-omap@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, vinod.koul@intel.com,
djbw@fb.com, grant.likely@linaro.org, rob.herring@calxeda.com,
devicetree@vger.kernel.org
Subject: Re: [PATCH v2] DMA: add help function to check whether dma controller registered
Date: Thu, 22 Aug 2013 14:36:53 -0600 [thread overview]
Message-ID: <52167665.90602@wwwdotorg.org> (raw)
In-Reply-To: <1377153781-18006-1-git-send-email-rizhao@nvidia.com>
On 08/22/2013 12:43 AM, Richard Zhao wrote:
> DMA client device driver usually needs to know at probe time whether
> dma controller has been registered to deffer probe. So add a help
> function of_dma_check_controller.
>
> DMA request channel functions can also used to check it, but they
> are usually called at open() time.
This new function is almost identical to the existing
of_dma_request_slave_channel(). Surely the code should be shared?
But that said, I don't see any need for a new function; why can't
drivers simply call of_dma_request_slave_channel() at probe time; from
what I can see, that function doesn't actually request the channel, but
rather simply looks it up, just like this one. The only difference is
that of_dma_xlate() is also called, but that's just doing some data
transformation, not actually recording channel ownership.
WARNING: multiple messages have this Message-ID (diff)
From: swarren@wwwdotorg.org (Stephen Warren)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v2] DMA: add help function to check whether dma controller registered
Date: Thu, 22 Aug 2013 14:36:53 -0600 [thread overview]
Message-ID: <52167665.90602@wwwdotorg.org> (raw)
In-Reply-To: <1377153781-18006-1-git-send-email-rizhao@nvidia.com>
On 08/22/2013 12:43 AM, Richard Zhao wrote:
> DMA client device driver usually needs to know at probe time whether
> dma controller has been registered to deffer probe. So add a help
> function of_dma_check_controller.
>
> DMA request channel functions can also used to check it, but they
> are usually called at open() time.
This new function is almost identical to the existing
of_dma_request_slave_channel(). Surely the code should be shared?
But that said, I don't see any need for a new function; why can't
drivers simply call of_dma_request_slave_channel() at probe time; from
what I can see, that function doesn't actually request the channel, but
rather simply looks it up, just like this one. The only difference is
that of_dma_xlate() is also called, but that's just doing some data
transformation, not actually recording channel ownership.
next prev parent reply other threads:[~2013-08-22 20:36 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-08-02 6:04 [PATCH] DMA: add help function to check whether dma controller registered Richard Zhao
2013-08-02 6:04 ` Richard Zhao
2013-08-02 19:59 ` Stephen Warren
2013-08-02 19:59 ` Stephen Warren
2013-08-05 5:56 ` Richard Zhao
2013-08-05 5:56 ` Richard Zhao
2013-08-22 6:43 ` [PATCH v2] " Richard Zhao
2013-08-22 6:43 ` Richard Zhao
2013-08-22 6:43 ` Richard Zhao
2013-08-22 20:36 ` Stephen Warren [this message]
2013-08-22 20:36 ` Stephen Warren
2013-08-23 1:17 ` Richard Zhao
2013-08-23 1:17 ` Richard Zhao
2013-08-23 15:56 ` Stephen Warren
2013-08-23 15:56 ` Stephen Warren
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