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From:   Eric Anholt <eric@anholt.net>
Date:   Thu, 5 Nov 2020 13:24:14 -0800
Message-ID: <CADaigPXM8NAZFAydXwcZt7ie_aK1aO8C=jqssA375sCMgU_gHw@mail.gmail.com>
Subject: Re: [PATCH v2] drm/vc4: replace idr_init() by idr_init_base()
To:     Deepak R Varma <mh12gx2825@gmail.com>
Cc:     David Airlie <airlied@linux.ie>, Daniel Vetter <daniel@ffwll.ch>,
        DRI Development <dri-devel@lists.freedesktop.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Maxime Ripard <mripard@kernel.org>,
        Maxime Ripard <maxime@cerno.tech>
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On Thu, Nov 5, 2020 at 12:21 PM Deepak R Varma <mh12gx2825@gmail.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@gmail.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@anholt.net>

hopefully Maxime can apply it.