linux-kernel - Re: [PATCH 1/3] resource: Add resource set range and size helpers

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Message-ID: <efab7a75-b01d-0649-dbbe-0154ab2b8587@linux.intel.com>
Date: Thu, 13 Jun 2024 16:55:35 +0300 (EEST)
From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To: Jonathan Cameron <Jonathan.Cameron@...wei.com>
cc: Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org, 
    Lorenzo Pieralisi <lpieralisi@...nel.org>, Rob Herring <robh@...nel.org>, 
    Krzysztof Wilczyński <kw@...ux.com>, 
    LKML <linux-kernel@...r.kernel.org>, 
    Jonathan Hunter <jonathanh@...dia.com>, 
    linux-arm-kernel@...ts.infradead.org, linux-tegra@...r.kernel.org, 
    Robert Richter <rric@...nel.org>, 
    Thierry Reding <thierry.reding@...il.com>, linux-cxl@...r.kernel.org
Subject: Re: [PATCH 1/3] resource: Add resource set range and size helpers

On Thu, 13 Jun 2024, Jonathan Cameron wrote:

> On Wed, 12 Jun 2024 11:56:27 +0300
> Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com> wrote:
> 
> > Setting the end address for a resource with a given size lacks a helper
> > and is therefore open coded unlike the getter side which has a helper
> > for resource size calculation. Also, almost all callsites that
> > calculate end address for a resource also set the start address right
> > before it like this:
> > 
> > 	res->start = start_addr;
> > 	res->end = res->start + size - 1;
> > 
> > Thus, add resource_set_range(res, start_addr, size) that sets the start
> > address and calculates the end address to simplify this often repeated
> > fragment. In addition, introduce resource_set_size() for the cases
> > where setting the start address of the resource is not necessary but
> > note resource_set_range() is preferred.
> > 
> > Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
> 
> We have a bunch of cases of this in CXL. Adding this helper seems like
> a good idea to me.

Sadly this won't help struct range cases which feature the same math.

> I'm not sure the odd semantics of resource_set_size() are a good idea.
> Maybe it could by naming hint that it's relying internally on
> size already being set.
> 
> resource_update_size() for instance might make people think or perhaps
> that's just more obscure.  Meh, I've argued myself around to there
> not being a better name.

Yeah, I tried to figure out solution to this very challenge too, but alas,
couldn't really find any good solution to it.

__ prefix would have kind of conveyed the meaning that you better know 
what you're doing but as some people oppose __ too, I didn't want to stir 
that pot. So it is what it is.

> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>`

FYI, I dropped the extra ` from that (no need to reply because of it).

Thanks for the reviews.

-- 
 i.


> > ---
> >  include/linux/ioport.h | 32 ++++++++++++++++++++++++++++++++
> >  1 file changed, 32 insertions(+)
> > 
> > diff --git a/include/linux/ioport.h b/include/linux/ioport.h
> > index db7fe25f3370..2a1d33ad151c 100644
> > --- a/include/linux/ioport.h
> > +++ b/include/linux/ioport.h
> > @@ -216,6 +216,38 @@ struct resource *lookup_resource(struct resource *root, resource_size_t start);
> >  int adjust_resource(struct resource *res, resource_size_t start,
> >  		    resource_size_t size);
> >  resource_size_t resource_alignment(struct resource *res);
> > +
> > +/**
> > + * resource_set_size - Calculates resource end address from size and start address
> > + * @res: The resource descriptor
> > + * @size: The size of the resource
> > + *
> > + * Calculates the end address for @res based on @size.
> > + *
> > + * Note: The start address of @res must be set when calling this function.
> > + * Use resource_set_range() if setting both the start address and @size.
> > + */
> > +static inline void resource_set_size(struct resource *res, resource_size_t size)
> > +{
> > +	res->end = res->start + size - 1;
> > +}
> > +
> > +/**
> > + * resource_set_range - Sets resource start and end addresses
> > + * @res: The resource descriptor
> > + * @start: The start address for the resource
> > + * @size: The size of the resource
> > + *
> > + * Sets @res start address and calculates the end address based on @size.
> > + */
> > +static inline void resource_set_range(struct resource *res,
> > +				      resource_size_t start,
> > +				      resource_size_t size)
> > +{
> > +	res->start = start;
> > +	resource_set_size(res, size);
> > +}
> > +
> >  static inline resource_size_t resource_size(const struct resource *res)
> >  {
> >  	return res->end - res->start + 1;
>