linux-kernel - Re: [PATCH 01/14] dmaengine: dma-jz4780: Avoid hardcoding number of channels

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Message-ID: <20180709165945.GH22377@vkoul-mobl>
Date:   Mon, 9 Jul 2018 22:29:45 +0530
From:   Vinod <vkoul@...nel.org>
To:     Paul Cercueil <paul@...pouillou.net>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Ralf Baechle <ralf@...ux-mips.org>,
        Paul Burton <paul.burton@...s.com>,
        James Hogan <jhogan@...nel.org>,
        Zubair Lutfullah Kakakhel <Zubair.Kakakhel@...tec.com>,
        Mathieu Malaterre <malat@...ian.org>,
        Daniel Silsby <dansilsby@...il.com>, dmaengine@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mips@...ux-mips.org
Subject: Re: [PATCH 01/14] dmaengine: dma-jz4780: Avoid hardcoding number of
 channels

On 03-07-18, 14:32, Paul Cercueil wrote:

>  struct jz4780_dma_dev {
>  	struct dma_device dma_device;
>  	void __iomem *base;
>  	struct clk *clk;
>  	unsigned int irq;
> +	unsigned int nb_channels;
> +	enum jz_version version;
>  
>  	uint32_t chan_reserved;
> -	struct jz4780_dma_chan chan[JZ_DMA_NR_CHANNELS];
> +	struct jz4780_dma_chan chan[];

why array, why not channel pointer?

> +static const unsigned int jz4780_dma_nb_channels[] = {
> +	[ID_JZ4780] = 32,
> +};
> +
> +static const struct of_device_id jz4780_dma_dt_match[] = {
> +	{ .compatible = "ingenic,jz4780-dma", .data = (void *)ID_JZ4780 },
> +	{},
> +};

Looking at description I was hoping that channels would be in DT,
channels is hardware information, so should come from DT rather than
coding the kernel...

> -	jzdma = devm_kzalloc(dev, sizeof(*jzdma), GFP_KERNEL);
> +	if (of_id)
> +		version = (enum jz_version)of_id->data;
> +	else
> +		version = ID_JZ4780; /* Default when not probed from DT */

where else would it be probed from.... ?
-- 
~Vinod