On Wed, 12 Jan 2022, Martinez, Ricardo wrote:

On 1/12/2022 10:16 AM, Ilpo Järvinen wrote:

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On Wed, 12 Jan 2022, Andy Shevchenko wrote:

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On Wed, Jan 12, 2022 at 04:24:52PM +0200, Ilpo Järvinen wrote:

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On Wed, 12 Jan 2022, Andy Shevchenko wrote:

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On Tue, Jan 11, 2022 at 08:55:58PM -0800, Martinez, Ricardo wrote:

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On 12/16/2021 3:08 AM, Ilpo Järvinen wrote:

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On Mon, 6 Dec 2021, Ricardo Martinez wrote:

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+	if (req->entry.next == &ring->gpd_ring)
+		return list_first_entry(&ring->gpd_ring, struct
cldma_request, entry);
+
+	return list_next_entry(req, entry);

...

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+	if (req->entry.prev == &ring->gpd_ring)
+		return list_last_entry(&ring->gpd_ring, struct
cldma_request, entry);
+
+	return list_prev_entry(req, entry);

...

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Wouldn't these two seems generic enough to warrant adding
something like
list_next/prev_entry_circular(...) to list.h?

Agree, in the upcoming version I'm planning to include something
like this
to list.h as suggested:

I think you mean for next and prev, i.o.w. two helpers, correct?

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#define list_next_entry_circular(pos, ptr, member) \

One thing I missed earlier, the sigrature should instead of ptr have head:
#define list_next_entry_circular(pos, head, member)

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     ((pos)->member.next == (ptr) ? \

I believe this is list_entry_is_head().

It takes .next so it's not the same as list_entry_is_head() and
list_entry_is_last() doesn't exist.

But we have list_last_entry(). So, what about

list_last_entry() == pos ? first : next;

and counterpart

list_first_entry() == pos ? last : prev;

?

Yes, although now that I think it more, using them implies the head
element has to be always accessed. It might be marginally cache friendlier
to use list_entry_is_head you originally suggested but get the next entry
first:
({
	typeof(pos) next__ = list_next_entry(pos, member); \
	!list_entry_is_head(next__, head, member) ? next__ :
list_next_entry(next__, member);
})
(This was written directly to email, entirely untested).

Here, the head element would only get accessed when we really need to walk
through it.

I'm not sure if list_next_entry() will work for the last element, what about
using list_is_last()?

Why wouldn't it? E.g., list_for_each_entry() does it for the last entry 
before terminating the for loop.

-- 
 i.

This way we avoid accessing head if not needed and does not to use
'container_of()' on (pos)->member.next.

    (list_is_last(&(pos)->member, head) ? \
    list_first_entry(head, typeof(*(pos)), member) : \
    list_next_entry(pos, member))

(untested)

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     list_first_entry(ptr, typeof(*(pos)), member) : \
     list_next_entry(pos, member))