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Date: Thu, 15 Oct 2015 09:37:08 +0530
From: Vinod Koul <vinod.koul@intel.com>
To: "M'boumba Cedric Madianga" <cedric.madianga@gmail.com>
Cc: Daniel Thompson <daniel.thompson@linaro.org>,
        Maxime Coquelin <mcoquelin.stm32@gmail.com>, robh+dt@kernel.org,
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        dmaengine@vger.kernel.org
Subject: Re: [PATCH v2 2/4] dmaengine: Add STM32 DMA driver
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On Wed, Oct 14, 2015 at 05:41:26PM +0200, M'boumba Cedric Madianga wrote:
> 2015-10-14 17:28 GMT+02:00 Daniel Thompson <daniel.thompson@linaro.org>:
> > On 14/10/15 16:26, M'boumba Cedric Madianga wrote:
> >>
> >> 2015-10-14 16:24 GMT+02:00 Daniel Thompson <daniel.thompson@linaro.org>:
> >>>
> >>>
> >>> Hmnnn...
> >>>
> >>> The dmaengine framework will WARN_ONCE() if an dmaengine is removed
> >>> whilst
> >>> it is active and also works hard to ensure dmaengine modules are not
> >>> removed
> >>> whilst there are active drivers using the framework.
> >>>
> >>> How do we get into this function whilst there is still an active DMA
> >>> channels?
> >>
> >>
> >> For example, when a user try "rmmod stm32-dma" in uart console.
> >> It will enter in stm32_dma_remove while there is potentially still active
> >> DMA.
> >
> >
> > Check dmaengine.c for yourself but I think in this case the dmaengine
> > framework will hold references to the module and prevent the remove from
> > taking place.
> 
> Yes I did it.
> As far I understand, the dmaengine framework will print a warning
> message but doesn't stop removing operation if there are some active
> clients.

we hold a ref, so removal wont work, see dma_chan_get()

-- 
~Vinod