Re: [PATCH V3 1/2] mtd: allow getting MTD device associated with a specific DT node

From: Ahmad Fatoum <a.fatoum@pengutronix.de>
To: "Rafał Miłecki" <zajec5@gmail.com>,
	"Srinivas Kandagatla" <srinivas.kandagatla@linaro.org>,
	"Miquel Raynal" <miquel.raynal@bootlin.com>,
	"Richard Weinberger" <richard@nod.at>,
	"Vignesh Raghavendra" <vigneshr@ti.com>
Cc: "Tom Rini" <trini@konsulko.com>,
	linux-arm-kernel@lists.infradead.org, u-boot@lists.denx.de,
	devicetree@vger.kernel.org, linux-mtd@lists.infradead.org,
	linux-kernel@vger.kernel.org, "Rafał Miłecki" <rafal@milecki.pl>,
	"Pengutronix Kernel Team" <kernel@pengutronix.de>
Subject: Re: [PATCH V3 1/2] mtd: allow getting MTD device associated with a specific DT node
Date: Tue, 14 Jun 2022 08:49:09 +0200	[thread overview]
Message-ID: <22ce9497-563f-0855-bec2-c56d4ddcfffa@pengutronix.de> (raw)
In-Reply-To: <20220611204651.19947-1-zajec5@gmail.com>

Hello Rafał,

On 11.06.22 22:46, Rafał Miłecki wrote:
> From: Rafał Miłecki <rafal@milecki.pl>
> 
> MTD subsystem API allows interacting with MTD devices (e.g. reading,
> writing, handling bad blocks). So far a random driver could get MTD
> device only by its name (get_mtd_device_nm()). This change allows
> getting them also by a DT node.
> 
> This API is required for drivers handling DT defined MTD partitions in a
> specific way (e.g. U-Boot (sub)partition with environment variables).
> 
> Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
> ---
> V3: First introduction of of_get_mtd_device_by_node()
> 
> mtd maintainers: please let know how would you like this patch
> processed. Would that be OK for you to Review/Ack it and let it go
> through NVMEM tree?
> ---
>  drivers/mtd/mtdcore.c   | 28 ++++++++++++++++++++++++++++
>  include/linux/mtd/mtd.h |  1 +
>  2 files changed, 29 insertions(+)
> 
> diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
> index 9eb0680db312..7dc214271c85 100644
> --- a/drivers/mtd/mtdcore.c
> +++ b/drivers/mtd/mtdcore.c
> @@ -1154,6 +1154,34 @@ int __get_mtd_device(struct mtd_info *mtd)
>  }
>  EXPORT_SYMBOL_GPL(__get_mtd_device);
>  
> +/**
> + * of_get_mtd_device_by_node - obtain an MTD device associated with a given node
> + *
> + * @np: device tree node
> + */
> +struct mtd_info *of_get_mtd_device_by_node(struct device_node *np)
> +{
> +	struct mtd_info *mtd = NULL;
> +	struct mtd_info *tmp;
> +	int err;
> +
> +	mutex_lock(&mtd_table_mutex);
> +
> +	err = -ENODEV;

Shouldn't this be -EPROBE_DEFER? That way drivers making
use of this function can defer probe until the device
is probed.

> +	mtd_for_each_device(tmp) {
> +		if (mtd_get_of_node(tmp) == np) {
> +			mtd = tmp;
> +			err = __get_mtd_device(mtd);
> +			break;
> +		}
> +	}
> +
> +	mutex_unlock(&mtd_table_mutex);
> +
> +	return err ? ERR_PTR(err) : mtd;
> +}
> +EXPORT_SYMBOL_GPL(of_get_mtd_device_by_node);
> +
>  /**
>   *	get_mtd_device_nm - obtain a validated handle for an MTD device by
>   *	device name
> diff --git a/include/linux/mtd/mtd.h b/include/linux/mtd/mtd.h
> index 955aee14b0f7..6fc841ceef31 100644
> --- a/include/linux/mtd/mtd.h
> +++ b/include/linux/mtd/mtd.h
> @@ -677,6 +677,7 @@ extern int mtd_device_unregister(struct mtd_info *master);
>  extern struct mtd_info *get_mtd_device(struct mtd_info *mtd, int num);
>  extern int __get_mtd_device(struct mtd_info *mtd);
>  extern void __put_mtd_device(struct mtd_info *mtd);
> +extern struct mtd_info *of_get_mtd_device_by_node(struct device_node *np);
>  extern struct mtd_info *get_mtd_device_nm(const char *name);
>  extern void put_mtd_device(struct mtd_info *mtd);
>  

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