[v2,1/4] i915: Move list_count() to list.h for broader use

  Some of the existing users, and definitely will be new ones, want to
count existing nodes in the list. Provide a generic API for that by
moving code from i915 to list.h.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
v2: dropped the duplicate code in i915 (LKP)
 drivers/gpu/drm/i915/gt/intel_engine_cs.c | 13 +------------
 include/linux/list.h                      | 13 +++++++++++++
 2 files changed, 14 insertions(+), 12 deletions(-)
  

>-----Original Message-----
>From: dri-devel <dri-devel-bounces@lists.freedesktop.org> On Behalf Of
>Andy Shevchenko
>Sent: Monday, November 14, 2022 11:22 AM
>To: Jakob Koschel <jakobkoschel@gmail.com>; Andy Shevchenko
><andriy.shevchenko@linux.intel.com>; Greg Kroah-Hartman
><gregkh@linuxfoundation.org>; Mathias Nyman
><mathias.nyman@linux.intel.com>; intel-gfx@lists.freedesktop.org; dri-
>devel@lists.freedesktop.org; linux-kernel@vger.kernel.org; linux-
>usb@vger.kernel.org
>Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>; Kevin Cernekee
><cernekee@gmail.com>; Nyman, Mathias <mathias.nyman@intel.com>; Vivi,
>Rodrigo <rodrigo.vivi@intel.com>; Andrew Morton <akpm@linux-
>foundation.org>
>Subject: [PATCH v2 1/4] i915: Move list_count() to list.h for broader use
>
>Some of the existing users, and definitely will be new ones, want to
>count existing nodes in the list. Provide a generic API for that by
>moving code from i915 to list.h.
>
>Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
>---
>v2: dropped the duplicate code in i915 (LKP)
> drivers/gpu/drm/i915/gt/intel_engine_cs.c | 13 +------------
> include/linux/list.h                      | 13 +++++++++++++
> 2 files changed, 14 insertions(+), 12 deletions(-)
>
>diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c
>b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
>index 6ae8b07cfaa1..b5d474be564d 100644
>--- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c
>+++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
>@@ -2085,17 +2085,6 @@ static void print_request_ring(struct drm_printer
>*m, struct i915_request *rq)
> 	}
> }
>
>-static unsigned long list_count(struct list_head *list)
>-{
>-	struct list_head *pos;
>-	unsigned long count = 0;
>-
>-	list_for_each(pos, list)
>-		count++;
>-
>-	return count;
>-}
>-
> static unsigned long read_ul(void *p, size_t x)
> {
> 	return *(unsigned long *)(p + x);
>@@ -2270,7 +2259,7 @@ void intel_engine_dump(struct intel_engine_cs
>*engine,
> 	spin_lock_irqsave(&engine->sched_engine->lock, flags);
> 	engine_dump_active_requests(engine, m);
>
>-	drm_printf(m, "\tOn hold?: %lu\n",
>+	drm_printf(m, "\tOn hold?: %zu\n",
> 		   list_count(&engine->sched_engine->hold));
> 	spin_unlock_irqrestore(&engine->sched_engine->lock, flags);
>
>diff --git a/include/linux/list.h b/include/linux/list.h
>index 61762054b4be..098eccf8c1b6 100644
>--- a/include/linux/list.h
>+++ b/include/linux/list.h
>@@ -655,6 +655,19 @@ static inline void list_splice_tail_init(struct list_head
>*list,
> 	     !list_is_head(pos, (head)); \
> 	     pos = n, n = pos->prev)
>
>+/**
>+ * list_count - count nodes in the list
>+ * @head:	the head for your list.
>+ */
>+#define list_count(head)		\
>+({					\
>+	struct list_head *__tmp;	\
>+	size_t __i = 0;			\
>+	list_for_each(__tmp, head)	\
>+		__i++;			\
>+	__i;				\
>+})

So all of the non-list_for_each code appears to be an inline.

This which, resembles the non-list_for_each pattern is a macro?

Just curious as to why the macro rather than inline?

Mike
+
> /**
>  * list_entry_is_head - test if the entry points to the head of the list
>  * @pos:	the type * to cursor
>--
>2.35.1
  

On Mon, Nov 14, 2022 at 06:11:51PM +0000, Ruhl, Michael J wrote:

...

> So all of the non-list_for_each code appears to be an inline.

This is not true.

> This which, resembles the non-list_for_each pattern is a macro?
> 
> Just curious as to why the macro rather than inline?

See above. However, I'm fine with the inline.
  

On Mon, 14 Nov 2022, Andy Shevchenko <andriy.shevchenko@linux.intel.com> wrote:
> Some of the existing users, and definitely will be new ones, want to
> count existing nodes in the list. Provide a generic API for that by
> moving code from i915 to list.h.

I think I'd find list_length() a much more natural name for this.

*shrug*

Acked-by: Jani Nikula <jani.nikula@intel.com>

regardless of what you decide to do with name or static inline etc.


>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> ---
> v2: dropped the duplicate code in i915 (LKP)
>  drivers/gpu/drm/i915/gt/intel_engine_cs.c | 13 +------------
>  include/linux/list.h                      | 13 +++++++++++++
>  2 files changed, 14 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> index 6ae8b07cfaa1..b5d474be564d 100644
> --- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> +++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> @@ -2085,17 +2085,6 @@ static void print_request_ring(struct drm_printer *m, struct i915_request *rq)
>  	}
>  }
>  
> -static unsigned long list_count(struct list_head *list)
> -{
> -	struct list_head *pos;
> -	unsigned long count = 0;
> -
> -	list_for_each(pos, list)
> -		count++;
> -
> -	return count;
> -}
> -
>  static unsigned long read_ul(void *p, size_t x)
>  {
>  	return *(unsigned long *)(p + x);
> @@ -2270,7 +2259,7 @@ void intel_engine_dump(struct intel_engine_cs *engine,
>  	spin_lock_irqsave(&engine->sched_engine->lock, flags);
>  	engine_dump_active_requests(engine, m);
>  
> -	drm_printf(m, "\tOn hold?: %lu\n",
> +	drm_printf(m, "\tOn hold?: %zu\n",
>  		   list_count(&engine->sched_engine->hold));
>  	spin_unlock_irqrestore(&engine->sched_engine->lock, flags);
>  
> diff --git a/include/linux/list.h b/include/linux/list.h
> index 61762054b4be..098eccf8c1b6 100644
> --- a/include/linux/list.h
> +++ b/include/linux/list.h
> @@ -655,6 +655,19 @@ static inline void list_splice_tail_init(struct list_head *list,
>  	     !list_is_head(pos, (head)); \
>  	     pos = n, n = pos->prev)
>  
> +/**
> + * list_count - count nodes in the list
> + * @head:	the head for your list.
> + */
> +#define list_count(head)		\
> +({					\
> +	struct list_head *__tmp;	\
> +	size_t __i = 0;			\
> +	list_for_each(__tmp, head)	\
> +		__i++;			\
> +	__i;				\
> +})
> +
>  /**
>   * list_entry_is_head - test if the entry points to the head of the list
>   * @pos:	the type * to cursor
  

On Tue, Nov 15, 2022 at 05:46:28PM +0200, Jani Nikula wrote:
> On Mon, 14 Nov 2022, Andy Shevchenko <andriy.shevchenko@linux.intel.com> wrote:
> > Some of the existing users, and definitely will be new ones, want to
> > count existing nodes in the list. Provide a generic API for that by
> > moving code from i915 to list.h.
> 
> I think I'd find list_length() a much more natural name for this.

i915 suggests my variant :-)

> *shrug*
> 
> Acked-by: Jani Nikula <jani.nikula@intel.com>
> 
> regardless of what you decide to do with name or static inline etc.

Thanks! I will check which one looks and feels better and update for v3.