Messages in this thread | | | From | Geert Uytterhoeven <> | Date | Fri, 18 May 2018 08:51:09 +0200 | Subject | Re: [PATCHv7] gpio: Remove VLA from gpiolib |
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Hi Laura,
On Fri, May 18, 2018 at 12:32 AM, Laura Abbott <labbott@redhat.com> wrote: > The new challenge is to remove VLAs from the kernel > (see https://lkml.org/lkml/2018/3/7/621) to eventually > turn on -Wvla. > > Using a kmalloc array is the easy way to fix this but kmalloc is still > more expensive than stack allocation. Introduce a fast path with a > fixed size stack array to cover most chip with gpios below some fixed > amount. The slow path dynamically allocates an array to cover those > chips with a large number of gpios. > > Reviewed-by: Phil Reid <preid@electromag.com.au> > Reviewed-and-tested-by: Lukas Wunner <lukas@wunner.de> > Signed-off-by: Lukas Wunner <lukas@wunner.de> > Signed-off-by: Laura Abbott <labbott@redhat.com> > --- > v7: Tweaked the Kconfig text to clarify the wording. Also fixed a few > other comments from Geert, including the earlier suggestion to reduce > the zeroing since I was wrong about that.
Thanks for the update!
With the minor nit below resolved: Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
> --- a/drivers/gpio/Kconfig > +++ b/drivers/gpio/Kconfig > @@ -22,6 +22,18 @@ menuconfig GPIOLIB > > if GPIOLIB > > +config GPIOLIB_FASTPATH_LIMIT > + int "Maximum number of GPIOs for fast path" > + range 16 512
While you can indeed fit 2 * 16 bits in a long, a lower limit of 16 doesn't make much sense, as you will use 2 longs (mask + bits) anyway. So please increase it to 32.
Gr{oetje,eeting}s,
Geert
-- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
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