linux-kernel - Re: [PATCH v3 1/3] memory: tegra: Add devm_tegra_get_memory

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Date:   Wed, 30 Sep 2020 11:07:32 +0200
From:   Krzysztof Kozlowski <krzk@...nel.org>
To:     Nicolin Chen <nicoleotsuka@...il.com>
Cc:     thierry.reding@...il.com, joro@...tes.org, digetx@...il.com,
        vdumpa@...dia.com, jonathanh@...dia.com,
        linux-tegra@...r.kernel.org, iommu@...ts.linux-foundation.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 1/3] memory: tegra: Add devm_tegra_get_memory_controller()

"On Wed, 30 Sep 2020 at 10:48, Nicolin Chen <nicoleotsuka@...il.com> wrote:
>
> From: Dmitry Osipenko <digetx@...il.com>
>
> Multiple Tegra drivers need to retrieve Memory Controller and hence there
> is quite some duplication of the retrieval code among the drivers. Let's
> add a new common helper for the retrieval of the MC.
>
> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
> Signed-off-by: Nicolin Chen <nicoleotsuka@...il.com>
> ---
>
> Changelog
> v2->v3:
>  * Replaced with Dimtry's devm_tegra_get_memory_controller()
> v1->v2:
>  * N/A
>
>  drivers/memory/tegra/mc.c | 39 +++++++++++++++++++++++++++++++++++++++
>  include/soc/tegra/mc.h    | 17 +++++++++++++++++
>  2 files changed, 56 insertions(+)
>
> diff --git a/drivers/memory/tegra/mc.c b/drivers/memory/tegra/mc.c
> index ec8403557ed4..dd691dc3738e 100644
> --- a/drivers/memory/tegra/mc.c
> +++ b/drivers/memory/tegra/mc.c
> @@ -42,6 +42,45 @@ static const struct of_device_id tegra_mc_of_match[] = {
>  };
>  MODULE_DEVICE_TABLE(of, tegra_mc_of_match);
>
> +static void tegra_mc_devm_action_put_device(void *data)

devm_tegra_memory_controller_put()

> +{
> +       struct tegra_mc *mc = data;
> +
> +       put_device(mc->dev);
> +}
> +
> +struct tegra_mc *devm_tegra_get_memory_controller(struct device *dev)

Usually 'get' is a suffix (e.g. clk, gpiod, iio, led), so:
devm_tegra_memory_controller_get()

> +{
> +       struct platform_device *pdev;
> +       struct device_node *np;
> +       struct tegra_mc *mc;
> +       int err;
> +
> +       np = of_find_matching_node_and_match(NULL, tegra_mc_of_match, NULL);
> +       if (!np)
> +               return ERR_PTR(-ENOENT);
> +
> +       pdev = of_find_device_by_node(np);
> +       of_node_put(np);
> +       if (!pdev)
> +               return ERR_PTR(-ENODEV);
> +
> +       mc = platform_get_drvdata(pdev);
> +       if (!mc) {
> +               put_device(mc->dev);
> +               return ERR_PTR(-EPROBE_DEFER);
> +       }
> +
> +       err = devm_add_action(dev, tegra_mc_devm_action_put_device, mc);
> +       if (err) {
> +               put_device(mc->dev);
> +               return ERR_PTR(err);
> +       }
> +
> +       return mc;
> +}
> +EXPORT_SYMBOL_GPL(devm_tegra_get_memory_controller);
> +
>  static int tegra_mc_block_dma_common(struct tegra_mc *mc,
>                                      const struct tegra_mc_reset *rst)
>  {
> diff --git a/include/soc/tegra/mc.h b/include/soc/tegra/mc.h
> index 1238e35653d1..c05142e3e244 100644
> --- a/include/soc/tegra/mc.h
> +++ b/include/soc/tegra/mc.h
> @@ -184,4 +184,21 @@ struct tegra_mc {
>  int tegra_mc_write_emem_configuration(struct tegra_mc *mc, unsigned long rate);
>  unsigned int tegra_mc_get_emem_device_count(struct tegra_mc *mc);
>
> +#ifdef CONFIG_TEGRA_MC
> +/**
> + * devm_tegra_get_memory_controller() - Get the tegra_mc pointer.
> + * @dev: Device that will be interacted with

This is not precise enough and there is no interaction with 'dev' in
devm_tegra_get_memory_controller(). Something like: "Device that owns
the pointer to tegra memory controller"

> + *
> + * Return: ERR_PTR() on error or a valid pointer to a struct tegra_mc.
> + *
> + * The mc->dev counter will be automatically put by the device management code.

1. s/mc/tegra_mc/ (it's the first occurence of word mc here)
2. "kerneldoc goes to the C file". Not to the header.

Best regards,
Krzysztof