Remove two unused pointers from struct cs_dsp_coeff_ctl by taking the
struct list_head out of struct cs_dsp_alg_region. On a x86_64 build
this saves 16 bytes per control.

Each cs_dsp_coeff_ctl instance needs to keep information about the
algorithm region it refers to. This is done by embedding an instance
of struct cs_dsp_alg_region. But cs_dsp_alg_region was also used to
store entries in a list of algorithm regions, and so had a struct
list_head object for that purpose. This list_head object is not used
with the embedded object in struct cs_dsp_alg_region so was just
wasted bytes.

A new struct cs_dsp_alg_region_list_item has been defined for creating
the list of algorithm regions. It contains a struct cs_dsp_alg_region
and a struct list_head.

Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
---
 drivers/firmware/cirrus/cs_dsp.c       | 45 ++++++++++++++------------
 include/linux/firmware/cirrus/cs_dsp.h |  2 --
 2 files changed, 25 insertions(+), 22 deletions(-)

diff --git a/drivers/firmware/cirrus/cs_dsp.c b/drivers/firmware/cirrus/cs_dsp.c
index 560724ce21aa..f51047d8ea64 100644
--- a/drivers/firmware/cirrus/cs_dsp.c
+++ b/drivers/firmware/cirrus/cs_dsp.c
@@ -311,6 +311,11 @@ static const struct cs_dsp_ops cs_dsp_adsp2_ops[];
 static const struct cs_dsp_ops cs_dsp_halo_ops;
 static const struct cs_dsp_ops cs_dsp_halo_ao_ops;
 
+struct cs_dsp_alg_region_list_item {
+	struct list_head list;
+	struct cs_dsp_alg_region alg_region;
+};
+
 struct cs_dsp_buf {
 	struct list_head list;
 	void *buf;
@@ -1752,13 +1757,13 @@ static void *cs_dsp_read_algs(struct cs_dsp *dsp, size_t n_algs,
 struct cs_dsp_alg_region *cs_dsp_find_alg_region(struct cs_dsp *dsp,
 						 int type, unsigned int id)
 {
-	struct cs_dsp_alg_region *alg_region;
+	struct cs_dsp_alg_region_list_item *item;
 
 	lockdep_assert_held(&dsp->pwr_lock);
 
-	list_for_each_entry(alg_region, &dsp->alg_regions, list) {
-		if (id == alg_region->alg && type == alg_region->type)
-			return alg_region;
+	list_for_each_entry(item, &dsp->alg_regions, list) {
+		if (id == item->alg_region.alg && type == item->alg_region.type)
+			return &item->alg_region;
 	}
 
 	return NULL;
@@ -1769,35 +1774,35 @@ static struct cs_dsp_alg_region *cs_dsp_create_region(struct cs_dsp *dsp,
 						      int type, __be32 id,
 						      __be32 ver, __be32 base)
 {
-	struct cs_dsp_alg_region *alg_region;
+	struct cs_dsp_alg_region_list_item *item;
 
-	alg_region = kzalloc(sizeof(*alg_region), GFP_KERNEL);
-	if (!alg_region)
+	item = kzalloc(sizeof(*item), GFP_KERNEL);
+	if (!item)
 		return ERR_PTR(-ENOMEM);
 
-	alg_region->type = type;
-	alg_region->alg = be32_to_cpu(id);
-	alg_region->ver = be32_to_cpu(ver);
-	alg_region->base = be32_to_cpu(base);
+	item->alg_region.type = type;
+	item->alg_region.alg = be32_to_cpu(id);
+	item->alg_region.ver = be32_to_cpu(ver);
+	item->alg_region.base = be32_to_cpu(base);
 
-	list_add_tail(&alg_region->list, &dsp->alg_regions);
+	list_add_tail(&item->list, &dsp->alg_regions);
 
 	if (dsp->wmfw_ver > 0)
-		cs_dsp_ctl_fixup_base(dsp, alg_region);
+		cs_dsp_ctl_fixup_base(dsp, &item->alg_region);
 
-	return alg_region;
+	return &item->alg_region;
 }
 
 static void cs_dsp_free_alg_regions(struct cs_dsp *dsp)
 {
-	struct cs_dsp_alg_region *alg_region;
+	struct cs_dsp_alg_region_list_item *item;
 
 	while (!list_empty(&dsp->alg_regions)) {
-		alg_region = list_first_entry(&dsp->alg_regions,
-					      struct cs_dsp_alg_region,
-					      list);
-		list_del(&alg_region->list);
-		kfree(alg_region);
+		item = list_first_entry(&dsp->alg_regions,
+					struct cs_dsp_alg_region_list_item,
+					list);
+		list_del(&item->list);
+		kfree(item);
 	}
 }
 
diff --git a/include/linux/firmware/cirrus/cs_dsp.h b/include/linux/firmware/cirrus/cs_dsp.h
index 7cae703b3137..a66eb7624730 100644
--- a/include/linux/firmware/cirrus/cs_dsp.h
+++ b/include/linux/firmware/cirrus/cs_dsp.h
@@ -64,14 +64,12 @@ struct cs_dsp_region {
 
 /**
  * struct cs_dsp_alg_region - Describes a logical algorithm region in DSP address space
- * @list:	List node for internal use
  * @alg:	Algorithm id
  * @ver:	Expected algorithm version
  * @type:	Memory region type
  * @base:	Address of region
  */
 struct cs_dsp_alg_region {
-	struct list_head list;
 	unsigned int alg;
 	unsigned int ver;
 	int type;
-- 
2.43.0

On Mon, 16 Jun 2025 11:30:52 +0100, Richard Fitzgerald wrote:
> Remove two unused pointers from struct cs_dsp_coeff_ctl by taking the
> struct list_head out of struct cs_dsp_alg_region. On a x86_64 build
> this saves 16 bytes per control.
> 
> Each cs_dsp_coeff_ctl instance needs to keep information about the
> algorithm region it refers to. This is done by embedding an instance
> of struct cs_dsp_alg_region. But cs_dsp_alg_region was also used to
> store entries in a list of algorithm regions, and so had a struct
> list_head object for that purpose. This list_head object is not used
> with the embedded object in struct cs_dsp_alg_region so was just
> wasted bytes.
> 
> [...]

Applied to

   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound.git for-next

Thanks!

[1/1] firmware: cs_dsp: Remove unused struct list_head from cs_dsp_coeff_ctl
      commit: e7af416aebb36e6681b9c6950d0f6352aee7c084

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark