dmaengine: hsu: use kzalloc_flex()

PATCH In review Rosen Penev 4 participants 6 messages Apr 15 – Apr 20

Subsystems (2)

dmaengine Intel MID (Mobile Internet Device) platform

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Rosen Penev

author

2026-04-15 03:28 UTC #0 lore raw

PATCH v4 1/1 dmaengine: hsu: use kzalloc_flex()

Simplifies allocations by using a flexible array member in this struct.

Remove hsu_dma_alloc_desc(). It now offers no readability advantages in this single usage.

Add __counted_by to get extra runtime analysis.

Apply the exact same treatment to struct hsu_dma and devm_kzalloc().

Signed-off-by Rosen Penev <[email protected]>

---
v4: move back counting variable assignment, as requested.
v3: update description.
v2: address review comments.

 drivers/dma/hsu/hsu.c | 43 +++++++++++--------------------------------
 drivers/dma/hsu/hsu.h |  4 ++--
 2 files changed, 13 insertions(+), 34 deletions(-)

drivers/dma/hsu/hsu.c +11 ~~-32~~

index f62d60d7bc6b..b1dd4fd1109b 100644
@@ -241,28 +241,10 @@ int hsu_dma_do_irq(struct hsu_dma_chip *chip, unsigned short nr, u32 status)
 }
 EXPORT_SYMBOL_GPL(hsu_dma_do_irq);
 
-static struct hsu_dma_desc *hsu_dma_alloc_desc(unsigned int nents)
-{
-	struct hsu_dma_desc *desc;
-
-	desc = kzalloc_obj(*desc, GFP_NOWAIT);
-	if (!desc)
-		return NULL;
-
-	desc->sg = kzalloc_objs(*desc->sg, nents, GFP_NOWAIT);
-	if (!desc->sg) {
-		kfree(desc);
-		return NULL;
-	}
-
-	return desc;
-}
-
 static void hsu_dma_desc_free(struct virt_dma_desc *vdesc)
 {
 	struct hsu_dma_desc *desc = to_hsu_dma_desc(vdesc);
 
-	kfree(desc->sg);
 	kfree(desc);
 }

@@ -276,10 +258,15 @@ static struct dma_async_tx_descriptor *hsu_dma_prep_slave_sg(
 	struct scatterlist *sg;
 	unsigned int i;
 
-	desc = hsu_dma_alloc_desc(sg_len);
+	desc = kzalloc_flex(*desc, sg, sg_len, GFP_NOWAIT);
 	if (!desc)
 		return NULL;
 
+	desc->nents = sg_len;
+	desc->direction = direction;
+	/* desc->active = 0 by kzalloc */
+	desc->status = DMA_IN_PROGRESS;
+
 	for_each_sg(sgl, sg, sg_len, i) {
 		desc->sg[i].addr = sg_dma_address(sg);
 		desc->sg[i].len = sg_dma_len(sg);

@@ -287,11 +274,6 @@ static struct dma_async_tx_descriptor *hsu_dma_prep_slave_sg(
 		desc->length += sg_dma_len(sg);
 	}
 
-	desc->nents = sg_len;
-	desc->direction = direction;
-	/* desc->active = 0 by kzalloc */
-	desc->status = DMA_IN_PROGRESS;
-
 	return vchan_tx_prep(&hsuc->vchan, &desc->vdesc, flags);
 }

@@ -428,22 +410,19 @@ int hsu_dma_probe(struct hsu_dma_chip *chip)
 {
 	struct hsu_dma *hsu;
 	void __iomem *addr = chip->regs + chip->offset;
+	unsigned short nr_channels;
 	unsigned short i;
 	int ret;
 
-	hsu = devm_kzalloc(chip->dev, sizeof(*hsu), GFP_KERNEL);
+	/* Calculate nr_channels from the IO space length */
+	nr_channels = (chip->length - chip->offset) / HSU_DMA_CHAN_LENGTH;
+	hsu = devm_kzalloc(chip->dev, struct_size(hsu, chan, nr_channels), GFP_KERNEL);
 	if (!hsu)
 		return -ENOMEM;
 
 	chip->hsu = hsu;
 
-	/* Calculate nr_channels from the IO space length */
-	hsu->nr_channels = (chip->length - chip->offset) / HSU_DMA_CHAN_LENGTH;
-
-	hsu->chan = devm_kcalloc(chip->dev, hsu->nr_channels,
-				 sizeof(*hsu->chan), GFP_KERNEL);
-	if (!hsu->chan)
-		return -ENOMEM;
+	hsu->nr_channels = nr_channels;
 
 	INIT_LIST_HEAD(&hsu->dma.channels);
 	for (i = 0; i < hsu->nr_channels; i++) {

drivers/dma/hsu/hsu.h +2 -2

index 3bca577b98a1..f6ca1014bccf 100644
@@ -71,11 +71,11 @@ struct hsu_dma_sg {
 struct hsu_dma_desc {
 	struct virt_dma_desc vdesc;
 	enum dma_transfer_direction direction;
-	struct hsu_dma_sg *sg;
 	unsigned int nents;
 	size_t length;
 	unsigned int active;
 	enum dma_status status;
+	struct hsu_dma_sg sg[] __counted_by(nents);
 };
 
 static inline struct hsu_dma_desc *to_hsu_dma_desc(struct virt_dma_desc *vdesc)

@@ -115,8 +115,8 @@ struct hsu_dma {
 	struct dma_device		dma;
 
 	/* channels */
-	struct hsu_dma_chan		*chan;
 	unsigned short			nr_channels;
+	struct hsu_dma_chan		chan[] __counted_by(nr_channels);
 };
 
 static inline struct hsu_dma *to_hsu_dma(struct dma_device *ddev)

--
2.53.0

Andy Shevchenko

Reviewed-by on v4 1/1

2026-04-15 04:49 UTC #1 lore raw

Quoted 8 lines · Rosen Penev

Simplifies allocations by using a flexible array member in this struct.
Remove hsu_dma_alloc_desc(). It now offers no readability advantages in this single usage.
Add __counted_by to get extra runtime analysis.
Apply the exact same treatment to struct hsu_dma and devm_kzalloc().

Reviewed-by Andy Shevchenko <[email protected]>

Signature · 2 lines

With Best Regards,
Andy Shevchenko

Frank Li

2026-04-20 06:14 UTC #2 lore raw

In reply to Rosen Penev

Subject

dmaengine: hsu: use kzalloc_flex() to simplify code

Quoted 1 line · Rosen Penev

Simplifies allocations by using a flexible array member in this struct.

%s/this struct/struct hsu_dma_sg and struct hsu_dma.

Frank

Quoted 137 lines

Remove hsu_dma_alloc_desc(). It now offers no readability advantages in this single usage.

Add __counted_by to get extra runtime analysis.

Apply the exact same treatment to struct hsu_dma and devm_kzalloc().

Signed-off-by Rosen Penev <[email protected]>

---
v4: move back counting variable assignment, as requested.
v3: update description.
v2: address review comments.

 drivers/dma/hsu/hsu.c | 43 +++++++++++--------------------------------
 drivers/dma/hsu/hsu.h |  4 ++--
 2 files changed, 13 insertions(+), 34 deletions(-)

drivers/dma/hsu/hsu.c +11 ~~-32~~

index f62d60d7bc6b..b1dd4fd1109b 100644
@@ -241,28 +241,10 @@ int hsu_dma_do_irq(struct hsu_dma_chip *chip, unsigned short nr, u32 status)
 }
 EXPORT_SYMBOL_GPL(hsu_dma_do_irq);
 
-static struct hsu_dma_desc *hsu_dma_alloc_desc(unsigned int nents)
-{
-	struct hsu_dma_desc *desc;
-
-	desc = kzalloc_obj(*desc, GFP_NOWAIT);
-	if (!desc)
-		return NULL;
-
-	desc->sg = kzalloc_objs(*desc->sg, nents, GFP_NOWAIT);
-	if (!desc->sg) {
-		kfree(desc);
-		return NULL;
-	}
-
-	return desc;
-}
-
 static void hsu_dma_desc_free(struct virt_dma_desc *vdesc)
 {
 	struct hsu_dma_desc *desc = to_hsu_dma_desc(vdesc);
 
-	kfree(desc->sg);
 	kfree(desc);
 }

@@ -276,10 +258,15 @@ static struct dma_async_tx_descriptor *hsu_dma_prep_slave_sg(
 	struct scatterlist *sg;
 	unsigned int i;
 
-	desc = hsu_dma_alloc_desc(sg_len);
+	desc = kzalloc_flex(*desc, sg, sg_len, GFP_NOWAIT);
 	if (!desc)
 		return NULL;
 
+	desc->nents = sg_len;
+	desc->direction = direction;
+	/* desc->active = 0 by kzalloc */
+	desc->status = DMA_IN_PROGRESS;
+
 	for_each_sg(sgl, sg, sg_len, i) {
 		desc->sg[i].addr = sg_dma_address(sg);
 		desc->sg[i].len = sg_dma_len(sg);

@@ -287,11 +274,6 @@ static struct dma_async_tx_descriptor *hsu_dma_prep_slave_sg(
 		desc->length += sg_dma_len(sg);
 	}
 
-	desc->nents = sg_len;
-	desc->direction = direction;
-	/* desc->active = 0 by kzalloc */
-	desc->status = DMA_IN_PROGRESS;
-
 	return vchan_tx_prep(&hsuc->vchan, &desc->vdesc, flags);
 }

@@ -428,22 +410,19 @@ int hsu_dma_probe(struct hsu_dma_chip *chip)
 {
 	struct hsu_dma *hsu;
 	void __iomem *addr = chip->regs + chip->offset;
+	unsigned short nr_channels;
 	unsigned short i;
 	int ret;
 
-	hsu = devm_kzalloc(chip->dev, sizeof(*hsu), GFP_KERNEL);
+	/* Calculate nr_channels from the IO space length */
+	nr_channels = (chip->length - chip->offset) / HSU_DMA_CHAN_LENGTH;
+	hsu = devm_kzalloc(chip->dev, struct_size(hsu, chan, nr_channels), GFP_KERNEL);
 	if (!hsu)
 		return -ENOMEM;
 
 	chip->hsu = hsu;
 
-	/* Calculate nr_channels from the IO space length */
-	hsu->nr_channels = (chip->length - chip->offset) / HSU_DMA_CHAN_LENGTH;
-
-	hsu->chan = devm_kcalloc(chip->dev, hsu->nr_channels,
-				 sizeof(*hsu->chan), GFP_KERNEL);
-	if (!hsu->chan)
-		return -ENOMEM;
+	hsu->nr_channels = nr_channels;
 
 	INIT_LIST_HEAD(&hsu->dma.channels);
 	for (i = 0; i < hsu->nr_channels; i++) {

drivers/dma/hsu/hsu.h +2 -3

index 3bca577b98a1..f6ca1014bccf 100644
@@ -71,11 +71,11 @@ struct hsu_dma_sg {
 struct hsu_dma_desc {
 	struct virt_dma_desc vdesc;
 	enum dma_transfer_direction direction;
-	struct hsu_dma_sg *sg;
 	unsigned int nents;
 	size_t length;
 	unsigned int active;
 	enum dma_status status;
+	struct hsu_dma_sg sg[] __counted_by(nents);
 };
 
 static inline struct hsu_dma_desc *to_hsu_dma_desc(struct virt_dma_desc *vdesc)

@@ -115,8 +115,8 @@ struct hsu_dma {
 	struct dma_device		dma;
 
 	/* channels */
-	struct hsu_dma_chan		*chan;
 	unsigned short			nr_channels;
+	struct hsu_dma_chan		chan[] __counted_by(nr_channels);
 };
 
 static inline struct hsu_dma *to_hsu_dma(struct dma_device *ddev)
--

2.53.0

Andy Shevchenko

2026-04-20 06:50 UTC #3 lore raw

Quoted 4 lines · Frank Li

Subject
dmaengine: hsu: use kzalloc_flex() to simplify code

Not really. The main point is to have source fortification being enabled.

Signature · 2 lines

With Best Regards,
Andy Shevchenko

Frank Li

2026-04-20 07:26 UTC #4 lore raw

Quoted 7 lines · Andy Shevchenko

Quoted 4 lines · Frank Li
Subject
dmaengine: hsu: use kzalloc_flex() to simplify code
Not really. The main point is to have source fortification being enabled.

Okay, but need know purpose in subject

use kzalloc_flex() to ....

Frank

Quoted 5 lines

--
With Best Regards,
Andy Shevchenko

Andy Shevchenko

2026-04-20 07:35 UTC #5 lore raw

Quoted 5 lines · Frank Li

Quoted 4 lines · Andy Shevchenko
Quoted 3 lines · Frank Li
Subject

Quoted 7 lines

Quoted 3 lines
Quoted 1 line
dmaengine: hsu: use kzalloc_flex() to simplify code
Not really. The main point is to have source fortification being enabled.
Okay, but need know purpose in subject
use kzalloc_flex() to ....

Not objecting this.

Signature · 2 lines

With Best Regards,
Andy Shevchenko