Re: [PATCH] staging: android: ion: Set the length of the DMA sg entries in buffer

From: Laura Abbott
Date: Thu Jan 21 2016 - 12:39:10 EST


On 01/21/2016 03:57 AM, Jon Medhurst (Tixy) wrote:
From: Liviu Dudau <Liviu.Dudau@xxxxxxx>

ion_buffer_create() will allocate a buffer and then create a DMA
mapping for it, but it forgot to set the length of the page entries.

Signed-off-by: Liviu Dudau <Liviu.Dudau@xxxxxxx>
Signed-off-by: Jon Medhurst <tixy@xxxxxxxxxx>
---
drivers/staging/android/ion/ion.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/android/ion/ion.c b/drivers/staging/android/ion/ion.c
index e237e9f..df56021 100644
--- a/drivers/staging/android/ion/ion.c
+++ b/drivers/staging/android/ion/ion.c
@@ -251,8 +251,10 @@ static struct ion_buffer *ion_buffer_create(struct ion_heap *heap,
* memory coming from the heaps is ready for dma, ie if it has a
* cached mapping that mapping has been invalidated
*/
- for_each_sg(buffer->sg_table->sgl, sg, buffer->sg_table->nents, i)
+ for_each_sg(buffer->sg_table->sgl, sg, buffer->sg_table->nents, i) {
sg_dma_address(sg) = sg_phys(sg);
+ sg_dma_len(sg) = sg->length;
+ }
mutex_lock(&dev->buffer_lock);
ion_buffer_add(dev, buffer);
mutex_unlock(&dev->buffer_lock);


So Ion is really doing it wrong by setting the sg_dma_address manually as
the comment above notes. Ion has moved away from sg_dma_len though
(see 06e0dcaeb4fd72a010a1f5ad0c03abd8e0a58ef9). This isn't technically
a mapping as well. What's broken by not having sg_dma_len set?

Thanks,
Laura