linux-kernel - Re: [PATCH v2] drm/vc4: replace idr_init() by idr_init

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Date:   Sun, 8 Nov 2020 15:43:51 +0530
From:   Deepak R Varma <mh12gx2825@...il.com>
To:     Maxime Ripard <maxime@...no.tech>
Cc:     Eric Anholt <eric@...olt.net>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        DRI Development <dri-devel@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] drm/vc4: replace idr_init() by idr_init_base()

On Fri, Nov 06, 2020 at 11:52:49AM +0100, Maxime Ripard wrote:
> On Thu, Nov 05, 2020 at 01:24:14PM -0800, Eric Anholt wrote:
> > On Thu, Nov 5, 2020 at 12:21 PM Deepak R Varma <mh12gx2825@...il.com> wrote:
> > >
> > > idr_init() uses base 0 which is an invalid identifier for this driver.
> > > The idr_alloc for this driver uses VC4_PERFMONID_MIN as start value for
> > > ID range and it is #defined to 1. The new function idr_init_base allows
> > > IDR to set the ID lookup from base 1. This avoids all lookups that
> > > otherwise starts from 0 since 0 is always unused / available.
> > >
> > > References: commit 6ce711f27500 ("idr: Make 1-based IDRs more efficient")
> > >
> > > Signed-off-by: Deepak R Varma <mh12gx2825@...il.com>
> > > ---
> > > Changes since v1:
> > >    - Change suggested by Eric Anholt
> > >      1. Use VC4_PERFMONID_MIN instead of magic number 1
> > >
> > >  drivers/gpu/drm/vc4/vc4_perfmon.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/gpu/drm/vc4/vc4_perfmon.c b/drivers/gpu/drm/vc4/vc4_perfmon.c
> > > index f4aa75efd16b..18abc06335c1 100644
> > > --- a/drivers/gpu/drm/vc4/vc4_perfmon.c
> > > +++ b/drivers/gpu/drm/vc4/vc4_perfmon.c
> > > @@ -77,7 +77,7 @@ struct vc4_perfmon *vc4_perfmon_find(struct vc4_file *vc4file, int id)
> > >  void vc4_perfmon_open_file(struct vc4_file *vc4file)
> > >  {
> > >         mutex_init(&vc4file->perfmon.lock);
> > > -       idr_init(&vc4file->perfmon.idr);
> > > +       idr_init_base(&vc4file->perfmon.idr, VC4_PERFMONID_MIN);
> > >  }
> > >
> > >  static int vc4_perfmon_idr_del(int id, void *elem, void *data)
> > > --
> > > 2.25.1
> > 
> > Reviewed-by: Eric Anholt <eric@...olt.net>
> > 
> > hopefully Maxime can apply it.
> 
> Applied, thanks!

Thank you all. Appreciate your time.

./drv

> Maxime