linux-kernel - Re: [PATCH 1/2] platform_device: add devres function region-reqs

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Date: Fri, 5 Jan 2024 20:11:50 +0100
From: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
To: Philipp Stanner <pstanner@...hat.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	"Rafael J. Wysocki" <rafael@...nel.org>, Laurentiu Palcu <laurentiu.palcu@....nxp.com>, 
	Lucas Stach <l.stach@...gutronix.de>, Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
	Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, 
	David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>, Shawn Guo <shawnguo@...nel.org>, 
	Sascha Hauer <s.hauer@...gutronix.de>, Pengutronix Kernel Team <kernel@...gutronix.de>, 
	Fabio Estevam <festevam@...il.com>, NXP Linux Team <linux-imx@....com>, 
	Mark Brown <broonie@...nel.org>, Takashi Iwai <tiwai@...e.de>, David Gow <davidgow@...gle.com>, 
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH 1/2] platform_device: add devres function region-reqs

On Fri, Jan 05, 2024 at 06:22:18PM +0100, Philipp Stanner wrote:
> Some drivers want to use (request) a region exclusively but nevertheless
> create several mappings within that region.
> 
> Currently, there is no managed devres function to request a region
> without mapping it.
> 
> Add the function devm_platform_get_resource()
> 
> Signed-off-by: Philipp Stanner <pstanner@...hat.com>
> ---
>  drivers/base/platform.c         | 37 +++++++++++++++++++++++++++++++++
>  include/linux/platform_device.h |  2 ++
>  2 files changed, 39 insertions(+)
> 
> diff --git a/drivers/base/platform.c b/drivers/base/platform.c
> index 10c577963418..243b9ec54d04 100644
> --- a/drivers/base/platform.c
> +++ b/drivers/base/platform.c
> @@ -82,6 +82,43 @@ struct resource *platform_get_mem_or_io(struct platform_device *dev,
>  }
>  EXPORT_SYMBOL_GPL(platform_get_mem_or_io);
>  
> +/**
> + * devm_platform_get_and_resource - get and request a resource

This function name is wrong.

> + *
> + * @pdev: the platform device to get the resource from
> + * @type: resource type (either IORESOURCE_MEM or IORESOURCE_IO)
> + * @num: resource index
> + * @name: name to be associated with the request
> + *
> + * Return: a pointer to the resource on success, an ERR_PTR on failure.
> + *
> + * Gets a resource and requests it. Use this instead of
> + * devm_platform_ioremap_resource() only if you have to create several single
> + * mappings with devm_ioremap().
> + */
> +struct resource *devm_platform_get_resource(struct platform_device *pdev,
> +		unsigned int type, unsigned int num, const char *name)
> +{
> +	struct resource *res;
> +
> +	res = platform_get_resource(pdev, type, num);
> +	if (!res)
> +		return ERR_PTR(-EINVAL);

From devm_platform_get_resource I'd expect that it only does
platform_get_resource() + register a cleanup function to undo it.

> +	if (type & IORESOURCE_MEM)
> +		res = devm_request_mem_region(&pdev->dev, res->start, res->end, name);
> +	else if (type & IORESOURCE_IO)
> +		res = devm_request_region(&pdev->dev, res->start, res->end, name);
> +	else
> +		return ERR_PTR(-EINVAL);

So this part is surprising. IMHO your function's name should include
"request".

> +	if (!res)
> +		return ERR_PTR(-EBUSY);
> +
> +	return res;
> +}
> +EXPORT_SYMBOL_GPL(devm_platform_get_resource);
> +
>  #ifdef CONFIG_HAS_IOMEM
>  /**
>   * devm_platform_get_and_ioremap_resource - call devm_ioremap_resource() for a

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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