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

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Message-ID: <3d0e251f0d58f1f8266074973644160d831fa462.camel@redhat.com>
Date: Mon, 08 Jan 2024 09:25:22 +0100
From: Philipp Stanner <pstanner@...hat.com>
To: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
Cc: dri-devel@...ts.freedesktop.org, Fabio Estevam <festevam@...il.com>, 
 "Rafael J. Wysocki" <rafael@...nel.org>, Greg Kroah-Hartman
 <gregkh@...uxfoundation.org>, Sascha Hauer <s.hauer@...gutronix.de>,
 linux-kernel@...r.kernel.org, Maxime Ripard <mripard@...nel.org>,  Mark
 Brown <broonie@...nel.org>, NXP Linux Team <linux-imx@....com>, Thomas
 Zimmermann <tzimmermann@...e.de>, Laurentiu Palcu
 <laurentiu.palcu@....nxp.com>, David Gow <davidgow@...gle.com>, Shawn Guo
 <shawnguo@...nel.org>, Pengutronix Kernel Team <kernel@...gutronix.de>,
 linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/2] platform_device: add devres function region-reqs

Hi

On Fri, 2024-01-05 at 20:11 +0100, Uwe Kleine-König wrote:
> 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".

Yes, that sounds very correct to me. I'll address that in v2


Thx for the feedback,

P.

> 
> > +       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
>