[PATCH v7 29/36] staging: ion: remove dead code

[PATCH v7 29/36] staging: ion: remove dead code

[Marek Szyprowski]

ion_heap_pages_zero() function is not used at all, so remove it to
simplify the ion_heap_sglist_zero() function later.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
---
 drivers/staging/android/ion/ion.h      | 1 -
 drivers/staging/android/ion/ion_heap.c | 9 ---------
 2 files changed, 10 deletions(-)

diff --git a/drivers/staging/android/ion/ion.h b/drivers/staging/android/ion/ion.h
index 74914a266e25..c199e88afc6c 100644
--- a/drivers/staging/android/ion/ion.h
+++ b/drivers/staging/android/ion/ion.h
@@ -177,7 +177,6 @@ void ion_heap_unmap_kernel(struct ion_heap *heap, struct ion_buffer *buffer);
 int ion_heap_map_user(struct ion_heap *heap, struct ion_buffer *buffer,
 		      struct vm_area_struct *vma);
 int ion_heap_buffer_zero(struct ion_buffer *buffer);
-int ion_heap_pages_zero(struct page *page, size_t size, pgprot_t pgprot);
 
 /**
  * ion_heap_init_shrinker
diff --git a/drivers/staging/android/ion/ion_heap.c b/drivers/staging/android/ion/ion_heap.c
index 0755b11348ed..9c23b2382a1e 100644
--- a/drivers/staging/android/ion/ion_heap.c
+++ b/drivers/staging/android/ion/ion_heap.c
@@ -145,15 +145,6 @@ int ion_heap_buffer_zero(struct ion_buffer *buffer)
 	return ion_heap_sglist_zero(table->sgl, table->nents, pgprot);
 }
 
-int ion_heap_pages_zero(struct page *page, size_t size, pgprot_t pgprot)
-{
-	struct scatterlist sg;
-
-	sg_init_table(&sg, 1);
-	sg_set_page(&sg, page, size, 0);
-	return ion_heap_sglist_zero(&sg, 1, pgprot);
-}
-
 void ion_heap_freelist_add(struct ion_heap *heap, struct ion_buffer *buffer)
 {
 	spin_lock(&heap->free_lock);
-- 
2.17.1

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[PATCH v7 30/36] staging: ion: fix common struct sg_table related issues

[Marek Szyprowski]

The Documentation/DMA-API-HOWTO.txt states that the dma_map_sg() function
returns the number of the created entries in the DMA address space.
However the subsequent calls to the dma_sync_sg_for_{device,cpu}() and
dma_unmap_sg must be called with the original number of the entries
passed to the dma_map_sg().

struct sg_table is a common structure used for describing a non-contiguous
memory buffer, used commonly in the DRM and graphics subsystems. It
consists of a scatterlist with memory pages and DMA addresses (sgl entry),
as well as the number of scatterlist entries: CPU pages (orig_nents entry)
and DMA mapped pages (nents entry).

It turned out that it was a common mistake to misuse nents and orig_nents
entries, calling DMA-mapping functions with a wrong number of entries or
ignoring the number of mapped entries returned by the dma_map_sg()
function.

To avoid such issues, lets use a common dma-mapping wrappers operating
directly on the struct sg_table objects and use scatterlist page
iterators where possible. This, almost always, hides references to the
nents and orig_nents entries, making the code robust, easier to follow
and copy/paste safe.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
---
 drivers/staging/android/ion/ion.c             | 25 +++++------
 drivers/staging/android/ion/ion_heap.c        | 44 ++++++-------------
 drivers/staging/android/ion/ion_system_heap.c |  2 +-
 3 files changed, 25 insertions(+), 46 deletions(-)

diff --git a/drivers/staging/android/ion/ion.c b/drivers/staging/android/ion/ion.c
index 38b51eace4f9..3c9f09506ffa 100644
--- a/drivers/staging/android/ion/ion.c
+++ b/drivers/staging/android/ion/ion.c
@@ -147,14 +147,14 @@ static struct sg_table *dup_sg_table(struct sg_table *table)
 	if (!new_table)
 		return ERR_PTR(-ENOMEM);
 
-	ret = sg_alloc_table(new_table, table->nents, GFP_KERNEL);
+	ret = sg_alloc_table(new_table, table->orig_nents, GFP_KERNEL);
 	if (ret) {
 		kfree(new_table);
 		return ERR_PTR(-ENOMEM);
 	}
 
 	new_sg = new_table->sgl;
-	for_each_sg(table->sgl, sg, table->nents, i) {
+	for_each_sgtable_sg(table, sg, i) {
 		memcpy(new_sg, sg, sizeof(*sg));
 		new_sg->dma_address = 0;
 		new_sg = sg_next(new_sg);
@@ -224,12 +224,13 @@ static struct sg_table *ion_map_dma_buf(struct dma_buf_attachment *attachment,
 {
 	struct ion_dma_buf_attachment *a = attachment->priv;
 	struct sg_table *table;
+	int ret;
 
 	table = a->table;
 
-	if (!dma_map_sg(attachment->dev, table->sgl, table->nents,
-			direction))
-		return ERR_PTR(-ENOMEM);
+	ret = dma_map_sgtable(attachment->dev, table, direction, 0);
+	if (ret)
+		return ERR_PTR(ret);
 
 	return table;
 }
@@ -238,7 +239,7 @@ static void ion_unmap_dma_buf(struct dma_buf_attachment *attachment,
 			      struct sg_table *table,
 			      enum dma_data_direction direction)
 {
-	dma_unmap_sg(attachment->dev, table->sgl, table->nents, direction);
+	dma_unmap_sgtable(attachment->dev, table, direction, 0);
 }
 
 static int ion_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma)
@@ -296,10 +297,8 @@ static int ion_dma_buf_begin_cpu_access(struct dma_buf *dmabuf,
 	}
 
 	mutex_lock(&buffer->lock);
-	list_for_each_entry(a, &buffer->attachments, list) {
-		dma_sync_sg_for_cpu(a->dev, a->table->sgl, a->table->nents,
-				    direction);
-	}
+	list_for_each_entry(a, &buffer->attachments, list)
+		dma_sync_sgtable_for_cpu(a->dev, a->table, direction);
 
 unlock:
 	mutex_unlock(&buffer->lock);
@@ -319,10 +318,8 @@ static int ion_dma_buf_end_cpu_access(struct dma_buf *dmabuf,
 	}
 
 	mutex_lock(&buffer->lock);
-	list_for_each_entry(a, &buffer->attachments, list) {
-		dma_sync_sg_for_device(a->dev, a->table->sgl, a->table->nents,
-				       direction);
-	}
+	list_for_each_entry(a, &buffer->attachments, list)
+		dma_sync_sgtable_for_device(a->dev, a->table, direction);
 	mutex_unlock(&buffer->lock);
 
 	return 0;
diff --git a/drivers/staging/android/ion/ion_heap.c b/drivers/staging/android/ion/ion_heap.c
index 9c23b2382a1e..79f27949edda 100644
--- a/drivers/staging/android/ion/ion_heap.c
+++ b/drivers/staging/android/ion/ion_heap.c
@@ -20,8 +20,7 @@
 void *ion_heap_map_kernel(struct ion_heap *heap,
 			  struct ion_buffer *buffer)
 {
-	struct scatterlist *sg;
-	int i, j;
+	struct sg_page_iter piter;
 	void *vaddr;
 	pgprot_t pgprot;
 	struct sg_table *table = buffer->sg_table;
@@ -38,14 +37,11 @@ void *ion_heap_map_kernel(struct ion_heap *heap,
 	else
 		pgprot = pgprot_writecombine(PAGE_KERNEL);
 
-	for_each_sg(table->sgl, sg, table->nents, i) {
-		int npages_this_entry = PAGE_ALIGN(sg->length) / PAGE_SIZE;
-		struct page *page = sg_page(sg);
-
-		BUG_ON(i >= npages);
-		for (j = 0; j < npages_this_entry; j++)
-			*(tmp++) = page++;
+	for_each_sgtable_page(table, &piter, 0) {
+		BUG_ON(tmp - pages >= npages);
+		*tmp++ = sg_page_iter_page(&piter);
 	}
+
 	vaddr = vmap(pages, npages, VM_MAP, pgprot);
 	vfree(pages);
 
@@ -64,32 +60,19 @@ void ion_heap_unmap_kernel(struct ion_heap *heap,
 int ion_heap_map_user(struct ion_heap *heap, struct ion_buffer *buffer,
 		      struct vm_area_struct *vma)
 {
+	struct sg_page_iter piter;
 	struct sg_table *table = buffer->sg_table;
 	unsigned long addr = vma->vm_start;
-	unsigned long offset = vma->vm_pgoff * PAGE_SIZE;
-	struct scatterlist *sg;
-	int i;
 	int ret;
 
-	for_each_sg(table->sgl, sg, table->nents, i) {
-		struct page *page = sg_page(sg);
-		unsigned long remainder = vma->vm_end - addr;
-		unsigned long len = sg->length;
+	for_each_sgtable_page(table, &piter, vma->vm_pgoff) {
+		struct page *page = sg_page_iter_page(&piter);
 
-		if (offset >= sg->length) {
-			offset -= sg->length;
-			continue;
-		} else if (offset) {
-			page += offset / PAGE_SIZE;
-			len = sg->length - offset;
-			offset = 0;
-		}
-		len = min(len, remainder);
-		ret = remap_pfn_range(vma, addr, page_to_pfn(page), len,
+		ret = remap_pfn_range(vma, addr, page_to_pfn(page), PAGE_SIZE,
 				      vma->vm_page_prot);
 		if (ret)
 			return ret;
-		addr += len;
+		addr += PAGE_SIZE;
 		if (addr >= vma->vm_end)
 			return 0;
 	}
@@ -109,15 +92,14 @@ static int ion_heap_clear_pages(struct page **pages, int num, pgprot_t pgprot)
 	return 0;
 }
 
-static int ion_heap_sglist_zero(struct scatterlist *sgl, unsigned int nents,
-				pgprot_t pgprot)
+static int ion_heap_sglist_zero(struct sg_table *sgt, pgprot_t pgprot)
 {
 	int p = 0;
 	int ret = 0;
 	struct sg_page_iter piter;
 	struct page *pages[32];
 
-	for_each_sg_page(sgl, &piter, nents, 0) {
+	for_each_sgtable_page(sgt, &piter, 0) {
 		pages[p++] = sg_page_iter_page(&piter);
 		if (p == ARRAY_SIZE(pages)) {
 			ret = ion_heap_clear_pages(pages, p, pgprot);
@@ -142,7 +124,7 @@ int ion_heap_buffer_zero(struct ion_buffer *buffer)
 	else
 		pgprot = pgprot_writecombine(PAGE_KERNEL);
 
-	return ion_heap_sglist_zero(table->sgl, table->nents, pgprot);
+	return ion_heap_sglist_zero(table, pgprot);
 }
 
 void ion_heap_freelist_add(struct ion_heap *heap, struct ion_buffer *buffer)
diff --git a/drivers/staging/android/ion/ion_system_heap.c b/drivers/staging/android/ion/ion_system_heap.c
index b83a1d16bd89..eac0632ab4e8 100644
--- a/drivers/staging/android/ion/ion_system_heap.c
+++ b/drivers/staging/android/ion/ion_system_heap.c
@@ -162,7 +162,7 @@ static void ion_system_heap_free(struct ion_buffer *buffer)
 	if (!(buffer->private_flags & ION_PRIV_FLAG_SHRINKER_FREE))
 		ion_heap_buffer_zero(buffer);
 
-	for_each_sg(table->sgl, sg, table->nents, i)
+	for_each_sgtable_sg(table, sg, i)
 		free_buffer_page(sys_heap, buffer, sg_page(sg));
 	sg_free_table(table);
 	kfree(table);
-- 
2.17.1

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[PATCH v7 31/36] staging: tegra-vde: fix common struct sg_table related issues

[Marek Szyprowski]

The Documentation/DMA-API-HOWTO.txt states that the dma_map_sg() function
returns the number of the created entries in the DMA address space.
However the subsequent calls to the dma_sync_sg_for_{device,cpu}() and
dma_unmap_sg must be called with the original number of the entries
passed to the dma_map_sg().

struct sg_table is a common structure used for describing a non-contiguous
memory buffer, used commonly in the DRM and graphics subsystems. It
consists of a scatterlist with memory pages and DMA addresses (sgl entry),
as well as the number of scatterlist entries: CPU pages (orig_nents entry)
and DMA mapped pages (nents entry).

It turned out that it was a common mistake to misuse nents and orig_nents
entries, calling DMA-mapping functions with a wrong number of entries or
ignoring the number of mapped entries returned by the dma_map_sg()
function.

To avoid such issues, lets use a common dma-mapping wrappers operating
directly on the struct sg_table objects and use scatterlist page
iterators where possible. This, almost always, hides references to the
nents and orig_nents entries, making the code robust, easier to follow
and copy/paste safe.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Dmitry Osipenko <digetx@gmail.com>
---
 drivers/staging/media/tegra-vde/iommu.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/media/tegra-vde/iommu.c b/drivers/staging/media/tegra-vde/iommu.c
index 6af863d92123..adf8dc7ee25c 100644
--- a/drivers/staging/media/tegra-vde/iommu.c
+++ b/drivers/staging/media/tegra-vde/iommu.c
@@ -36,8 +36,8 @@ int tegra_vde_iommu_map(struct tegra_vde *vde,
 
 	addr = iova_dma_addr(&vde->iova, iova);
 
-	size = iommu_map_sg(vde->domain, addr, sgt->sgl, sgt->nents,
-			    IOMMU_READ | IOMMU_WRITE);
+	size = iommu_map_sgtable(vde->domain, addr, sgt,
+				 IOMMU_READ | IOMMU_WRITE);
 	if (!size) {
 		__free_iova(&vde->iova, iova);
 		return -ENXIO;
-- 
2.17.1

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Re: [PATCH v7 31/36] staging: tegra-vde: fix common struct sg_table related issues

[kernel test robot]

[-- Attachment #1: Type: text/plain, Size: 2655 bytes --]

Hi Marek,

I love your patch! Yet something to improve:

[auto build test ERROR on next-20200618]
[also build test ERROR on v5.8-rc1]
[cannot apply to linuxtv-media/master staging/staging-testing drm-exynos/exynos-drm-next drm-intel/for-linux-next linus/master v5.8-rc1 v5.7 v5.7-rc7]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use  as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Marek-Szyprowski/DRM-fix-struct-sg_table-nents-vs-orig_nents-misuse/20200619-184302
base:    ce2cc8efd7a40cbd17841add878cb691d0ce0bba
config: c6x-allyesconfig (attached as .config)
compiler: c6x-elf-gcc (GCC) 9.3.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=c6x 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   drivers/staging/media/tegra-vde/iommu.c: In function 'tegra_vde_iommu_map':
>> drivers/staging/media/tegra-vde/iommu.c:39:9: error: implicit declaration of function 'iommu_map_sgtable'; did you mean 'dma_map_sgtable'? [-Werror=implicit-function-declaration]
      39 |  size = iommu_map_sgtable(vde->domain, addr, sgt,
         |         ^~~~~~~~~~~~~~~~~
         |         dma_map_sgtable
   cc1: some warnings being treated as errors

vim +39 drivers/staging/media/tegra-vde/iommu.c

    18	
    19	int tegra_vde_iommu_map(struct tegra_vde *vde,
    20				struct sg_table *sgt,
    21				struct iova **iovap,
    22				size_t size)
    23	{
    24		struct iova *iova;
    25		unsigned long shift;
    26		unsigned long end;
    27		dma_addr_t addr;
    28	
    29		end = vde->domain->geometry.aperture_end;
    30		size = iova_align(&vde->iova, size);
    31		shift = iova_shift(&vde->iova);
    32	
    33		iova = alloc_iova(&vde->iova, size >> shift, end >> shift, true);
    34		if (!iova)
    35			return -ENOMEM;
    36	
    37		addr = iova_dma_addr(&vde->iova, iova);
    38	
  > 39		size = iommu_map_sgtable(vde->domain, addr, sgt,
    40					 IOMMU_READ | IOMMU_WRITE);
    41		if (!size) {
    42			__free_iova(&vde->iova, iova);
    43			return -ENXIO;
    44		}
    45	
    46		*iovap = iova;
    47	
    48		return 0;
    49	}
    50	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

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Re: [PATCH v7 31/36] staging: tegra-vde: fix common struct sg_table related issues

[Dmitry Osipenko]

В Fri, 19 Jun 2020 12:36:31 +0200
Marek Szyprowski <m.szyprowski@samsung.com> пишет:

> The Documentation/DMA-API-HOWTO.txt states that the dma_map_sg()
> function returns the number of the created entries in the DMA address
> space. However the subsequent calls to the
> dma_sync_sg_for_{device,cpu}() and dma_unmap_sg must be called with
> the original number of the entries passed to the dma_map_sg().
> 
> struct sg_table is a common structure used for describing a
> non-contiguous memory buffer, used commonly in the DRM and graphics
> subsystems. It consists of a scatterlist with memory pages and DMA
> addresses (sgl entry), as well as the number of scatterlist entries:
> CPU pages (orig_nents entry) and DMA mapped pages (nents entry).
> 
> It turned out that it was a common mistake to misuse nents and
> orig_nents entries, calling DMA-mapping functions with a wrong number
> of entries or ignoring the number of mapped entries returned by the
> dma_map_sg() function.
> 
> To avoid such issues, lets use a common dma-mapping wrappers operating
> directly on the struct sg_table objects and use scatterlist page
> iterators where possible. This, almost always, hides references to the
> nents and orig_nents entries, making the code robust, easier to follow
> and copy/paste safe.
> 
> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
> Reviewed-by: Dmitry Osipenko <digetx@gmail.com>
> ---
>  drivers/staging/media/tegra-vde/iommu.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/staging/media/tegra-vde/iommu.c
> b/drivers/staging/media/tegra-vde/iommu.c index
> 6af863d92123..adf8dc7ee25c 100644 ---
> a/drivers/staging/media/tegra-vde/iommu.c +++
> b/drivers/staging/media/tegra-vde/iommu.c @@ -36,8 +36,8 @@ int
> tegra_vde_iommu_map(struct tegra_vde *vde, 
>  	addr = iova_dma_addr(&vde->iova, iova);
>  
> -	size = iommu_map_sg(vde->domain, addr, sgt->sgl, sgt->nents,
> -			    IOMMU_READ | IOMMU_WRITE);
> +	size = iommu_map_sgtable(vde->domain, addr, sgt,
> +				 IOMMU_READ | IOMMU_WRITE);
>  	if (!size) {
>  		__free_iova(&vde->iova, iova);
>  		return -ENXIO;

Ahh, I saw the build failure report. You're changing the DMA API in
this series, while DMA API isn't used by this driver, it uses IOMMU
API. Hence there is no need to touch this code. Similar problem in the
host1x driver patch.
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Re: [PATCH v7 31/36] staging: tegra-vde: fix common struct sg_table related issues

[Marek Szyprowski]

On 21.06.2020 06:00, Dmitry Osipenko wrote:
> В Fri, 19 Jun 2020 12:36:31 +0200
> Marek Szyprowski <m.szyprowski@samsung.com> пишет:
>
>> The Documentation/DMA-API-HOWTO.txt states that the dma_map_sg()
>> function returns the number of the created entries in the DMA address
>> space. However the subsequent calls to the
>> dma_sync_sg_for_{device,cpu}() and dma_unmap_sg must be called with
>> the original number of the entries passed to the dma_map_sg().
>>
>> struct sg_table is a common structure used for describing a
>> non-contiguous memory buffer, used commonly in the DRM and graphics
>> subsystems. It consists of a scatterlist with memory pages and DMA
>> addresses (sgl entry), as well as the number of scatterlist entries:
>> CPU pages (orig_nents entry) and DMA mapped pages (nents entry).
>>
>> It turned out that it was a common mistake to misuse nents and
>> orig_nents entries, calling DMA-mapping functions with a wrong number
>> of entries or ignoring the number of mapped entries returned by the
>> dma_map_sg() function.
>>
>> To avoid such issues, lets use a common dma-mapping wrappers operating
>> directly on the struct sg_table objects and use scatterlist page
>> iterators where possible. This, almost always, hides references to the
>> nents and orig_nents entries, making the code robust, easier to follow
>> and copy/paste safe.
>>
>> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
>> Reviewed-by: Dmitry Osipenko <digetx@gmail.com>
>> ---
>>   drivers/staging/media/tegra-vde/iommu.c | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/staging/media/tegra-vde/iommu.c
>> b/drivers/staging/media/tegra-vde/iommu.c index
>> 6af863d92123..adf8dc7ee25c 100644 ---
>> a/drivers/staging/media/tegra-vde/iommu.c +++
>> b/drivers/staging/media/tegra-vde/iommu.c @@ -36,8 +36,8 @@ int
>> tegra_vde_iommu_map(struct tegra_vde *vde,
>>   	addr = iova_dma_addr(&vde->iova, iova);
>>   
>> -	size = iommu_map_sg(vde->domain, addr, sgt->sgl, sgt->nents,
>> -			    IOMMU_READ | IOMMU_WRITE);
>> +	size = iommu_map_sgtable(vde->domain, addr, sgt,
>> +				 IOMMU_READ | IOMMU_WRITE);
>>   	if (!size) {
>>   		__free_iova(&vde->iova, iova);
>>   		return -ENXIO;
> Ahh, I saw the build failure report. You're changing the DMA API in
> this series, while DMA API isn't used by this driver, it uses IOMMU
> API. Hence there is no need to touch this code. Similar problem in the
> host1x driver patch.

The issue is caused by the lack of iommu_map_sgtable() stub when no 
IOMMU support is configured. I've posted a patch for this:

https://lore.kernel.org/lkml/20200630081756.18526-1-m.szyprowski@samsung.com/

The patch for this driver is fine, we have to wait until the above fix 
gets merged and then it can be applied during the next release cycle.

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland

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Re: [PATCH v7 31/36] staging: tegra-vde: fix common struct sg_table related issues

[Dmitry Osipenko]

30.06.2020 13:07, Marek Szyprowski пишет:
> On 21.06.2020 06:00, Dmitry Osipenko wrote:
>> В Fri, 19 Jun 2020 12:36:31 +0200
>> Marek Szyprowski <m.szyprowski@samsung.com> пишет:
>>
>>> The Documentation/DMA-API-HOWTO.txt states that the dma_map_sg()
>>> function returns the number of the created entries in the DMA address
>>> space. However the subsequent calls to the
>>> dma_sync_sg_for_{device,cpu}() and dma_unmap_sg must be called with
>>> the original number of the entries passed to the dma_map_sg().
>>>
>>> struct sg_table is a common structure used for describing a
>>> non-contiguous memory buffer, used commonly in the DRM and graphics
>>> subsystems. It consists of a scatterlist with memory pages and DMA
>>> addresses (sgl entry), as well as the number of scatterlist entries:
>>> CPU pages (orig_nents entry) and DMA mapped pages (nents entry).
>>>
>>> It turned out that it was a common mistake to misuse nents and
>>> orig_nents entries, calling DMA-mapping functions with a wrong number
>>> of entries or ignoring the number of mapped entries returned by the
>>> dma_map_sg() function.
>>>
>>> To avoid such issues, lets use a common dma-mapping wrappers operating
>>> directly on the struct sg_table objects and use scatterlist page
>>> iterators where possible. This, almost always, hides references to the
>>> nents and orig_nents entries, making the code robust, easier to follow
>>> and copy/paste safe.
>>>
>>> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
>>> Reviewed-by: Dmitry Osipenko <digetx@gmail.com>
>>> ---
>>>   drivers/staging/media/tegra-vde/iommu.c | 4 ++--
>>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/staging/media/tegra-vde/iommu.c
>>> b/drivers/staging/media/tegra-vde/iommu.c index
>>> 6af863d92123..adf8dc7ee25c 100644 ---
>>> a/drivers/staging/media/tegra-vde/iommu.c +++
>>> b/drivers/staging/media/tegra-vde/iommu.c @@ -36,8 +36,8 @@ int
>>> tegra_vde_iommu_map(struct tegra_vde *vde,
>>>   	addr = iova_dma_addr(&vde->iova, iova);
>>>   
>>> -	size = iommu_map_sg(vde->domain, addr, sgt->sgl, sgt->nents,
>>> -			    IOMMU_READ | IOMMU_WRITE);
>>> +	size = iommu_map_sgtable(vde->domain, addr, sgt,
>>> +				 IOMMU_READ | IOMMU_WRITE);
>>>   	if (!size) {
>>>   		__free_iova(&vde->iova, iova);
>>>   		return -ENXIO;
>> Ahh, I saw the build failure report. You're changing the DMA API in
>> this series, while DMA API isn't used by this driver, it uses IOMMU
>> API. Hence there is no need to touch this code. Similar problem in the
>> host1x driver patch.
> 
> The issue is caused by the lack of iommu_map_sgtable() stub when no 
> IOMMU support is configured. I've posted a patch for this:
> 
> https://lore.kernel.org/lkml/20200630081756.18526-1-m.szyprowski@samsung.com/
> 
> The patch for this driver is fine, we have to wait until the above fix 
> gets merged and then it can be applied during the next release cycle.

Thank you for the clarification!
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