Re: [PATCH] gpio: Remove dynamic allocation from populate_parent_alloc_arg()

[Linus Walleij]

On Sat, May 14, 2022 at 12:36 PM Marc Zyngier <maz@xxxxxxxxxx> wrote:
> On Fri, 13 May 2022 22:24:40 +0100,
> Linus Walleij <linus.walleij@xxxxxxxxxx> wrote:
> >
> > On Thu, May 12, 2022 at 6:23 PM Marc Zyngier <maz@xxxxxxxxxx> wrote:
> >
> > > The gpiolib is unique in the way it uses intermediate fwspecs
> > > when feeding an interrupt specifier to the parent domain, as it
> > > relies on the populate_parent_alloc_arg() callback to perform
> > > a dynamic allocation.
> > >
> > > THis is pretty inefficient (we free the structure almost immediately),
> > > and the only reason this isn't a stack allocation is that our
> > > ThunderX friend uses MSIs rather than a FW-constructed structure.
> > >
> > > Let's solve it by providing a new type composed of the union
> > > of a struct irq_fwspec and a msi_info_t, which satisfies both
> > > requirements. This allows us to use a stack allocation, and we
> > > can move the handful of users to this new scheme.
> > >
> > > Also perform some additional cleanup, such as getting rid of the
> > > stub versions of the irq_domain_translate_*cell helpers, which
> > > are never used when CONFIG_IRQ_DOMAIN_HIERARCHY isn't selected.
> > >
> > > Tested on a Tegra186.
> > >
> > > Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
> > > Cc: Daniel Palmer <daniel@xxxxxxxxx>
> > > Cc: Romain Perier <romain.perier@xxxxxxxxx>
> > > Cc: Linus Walleij <linus.walleij@xxxxxxxxxx>
> > > Cc: Bartosz Golaszewski <brgl@xxxxxxxx>
> > > Cc: Thierry Reding <thierry.reding@xxxxxxxxx>
> > > Cc: Jonathan Hunter <jonathanh@xxxxxxxxxx>
> > > Cc: Robert Richter <rric@xxxxxxxxxx>
> > > Cc: Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@xxxxxxxxxxxxx>
> > > Cc: Andy Gross <agross@xxxxxxxxxx>
> > > Cc: Bjorn Andersson <bjorn.andersson@xxxxxxxxxx>
> >
> > This looks very appetizing to me but:
> >
> > drivers/pinctrl/qcom/pinctrl-spmi-gpio.c | 15 ++++-----
> >
> > This seems to have some changes to
> > ->populate_parent_alloc_arg not even in linux-next,
> > so I get confused, what are the prerequisites? (Probably
> > something I already reviewed, but...)
>
> Odd. This patch is on top of irqchip-next, which is itself already in
> -next (you got me worried and I just pulled everything to check).

I confused it with pinctrl-ssbi-gpio.c. Simple beginners mistake.
Reviewed-by: Linus Walleij <linus.walleij@xxxxxxxxxx>

Yours,
Linus Walleij