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From: =?UTF-8?q?Ilpo=20J=C3=A4rvinen?= <ilpo.jarvinen@linux.intel.com>
Date: Thu, 13 Jun 2024 16:55:35 +0300 (EEST)
To: Jonathan Cameron <Jonathan.Cameron@Huawei.com>
cc: Bjorn Helgaas <bhelgaas@google.com>, linux-pci@vger.kernel.org, 
    Lorenzo Pieralisi <lpieralisi@kernel.org>, Rob Herring <robh@kernel.org>, 
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    LKML <linux-kernel@vger.kernel.org>, 
    Jonathan Hunter <jonathanh@nvidia.com>, 
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    Robert Richter <rric@kernel.org>, 
    Thierry Reding <thierry.reding@gmail.com>, linux-cxl@vger.kernel.org
Subject: Re: [PATCH 1/3] resource: Add resource set range and size helpers
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On Thu, 13 Jun 2024, Jonathan Cameron wrote:

> On Wed, 12 Jun 2024 11:56:27 +0300
> Ilpo J=E4rvinen <ilpo.jarvinen@linux.intel.com> wrote:
>=20
> > 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:
> >=20
> > =09res->start =3D start_addr;
> > =09res->end =3D res->start + size - 1;
> >=20
> > 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.
> >=20
> > Signed-off-by: Ilpo J=E4rvinen <ilpo.jarvinen@linux.intel.com>
>=20
> 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.
>=20
> 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=20
what you're doing but as some people oppose __ too, I didn't want to stir=
=20
that pot. So it is what it is.

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

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

Thanks for the reviews.

--=20
 i.


> > ---
> >  include/linux/ioport.h | 32 ++++++++++++++++++++++++++++++++
> >  1 file changed, 32 insertions(+)
> >=20
> > 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,
> >  =09=09    resource_size_t size);
> >  resource_size_t resource_alignment(struct resource *res);
> > +
> > +/**
> > + * resource_set_size - Calculates resource end address from size and s=
tart 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 funct=
ion.
> > + * Use resource_set_range() if setting both the start address and @siz=
e.
> > + */
> > +static inline void resource_set_size(struct resource *res, resource_si=
ze_t size)
> > +{
> > +=09res->end =3D 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 @si=
ze.
> > + */
> > +static inline void resource_set_range(struct resource *res,
> > +=09=09=09=09      resource_size_t start,
> > +=09=09=09=09      resource_size_t size)
> > +{
> > +=09res->start =3D start;
> > +=09resource_set_size(res, size);
> > +}
> > +
> >  static inline resource_size_t resource_size(const struct resource *res=
)
> >  {
> >  =09return res->end - res->start + 1;
>=20
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