linux-kernel - Re: [PATCH 2/5] dmaengine: Add STM32 DMAMUX driver

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Message-ID: <20170501060353.GO6263@localhost>
Date:   Mon, 1 May 2017 11:33:53 +0530
From:   Vinod Koul <vinod.koul@...el.com>
To:     Pierre Yves MORDRET <pierre-yves.mordret@...com>
Cc:     M'boumba Cedric Madianga <cedric.madianga@...il.com>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Alexandre TORGUE <alexandre.torgue@...com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "mcoquelin.stm32@...il.com" <mcoquelin.stm32@...il.com>,
        "dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>,
        "dan.j.williams@...el.com" <dan.j.williams@...el.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 2/5] dmaengine: Add STM32 DMAMUX driver

On Wed, Apr 26, 2017 at 09:17:37AM +0000, Pierre Yves MORDRET wrote:
> >> +
> >> +	ret = of_property_read_u32(node, "dma-channels",
> >> +				   &dmamux->dmamux_channels);
> >
> > can we have property_xxx calls alone, that way driver is not strictly
> > dependent on of
> 
> Can you please explain what you are asking for ? Not sure to understand 
> correctly.

Use device_property_read_u32() which is a generic property API.


> >> +static int __init stm32_dmamux_init(void)
> >> +{
> >> +	return platform_driver_register(&stm32_dmamux_driver);
> >> +}
> >> +arch_initcall(stm32_dmamux_init);
> >
> > why not module init, wouldnt defer probe solve the dependencies
> >
> 
> The reason behind many devices (device_initcall level) rely on DMAs. If 
> init is deferred DMAMUX driver will be probed twice if dependents rely 
> on it. This sounds not a good call. This explains arch_initcall level.

Why not deferred probe was introduced to help with dependencies...

-- 
~Vinod