linux-kernel - Re: [PATCH v3 03/18] dmaengine: dma-jz4780: Avoid hardcoding number of channels

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Date:   Tue, 24 Jul 2018 18:52:59 +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 v3 03/18] dmaengine: dma-jz4780: Avoid hardcoding number
 of channels

On 21-07-18, 13:06, Paul Cercueil wrote:

> +static const struct jz4780_dma_soc_data jz4780_dma_soc_data[] = {
> +	[ID_JZ4780] = { .nb_channels = 32, },

why the array of structs?

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

the data should be jz4780_dma_soc_data? as you would add more data
later.. and not the enum..

> -	jzdma = devm_kzalloc(dev, sizeof(*jzdma), GFP_KERNEL);
> +	version = (enum jz_version)of_id->data;
> +	soc_data = &jz4780_dma_soc_data[version];

this can be simplified if we do:

        soc_data = device_get_match_data(pdev);

with:

static const struct jz4780_dma_soc_data jz4780_dma_soc_data = {
        .nb_channels = 32,
};

and
        { .compatible = "ingenic,jz4780-dma", .data = (void *)jz4780_dma_soc_data },

You add more parameters in future patches and store soc_data in driver
object and use as is..

> +	jzdma = devm_kzalloc(dev, sizeof(*jzdma)
> +				+ sizeof(*jzdma->chan) * soc_data->nb_channels,
> +				GFP_KERNEL);
>  	if (!jzdma)
>  		return -ENOMEM;
>  
> +	jzdma->soc_data = soc_data;
> +	jzdma->version = version;

why do you need to store version, driver should handle values and not
versions..

-- 
~Vinod