On Fri, Jul 20, 2012 at 10:09 PM, Rob Clark [off-list ref] wrote:

Fyi, Daniel Vetter had suggested on IRC that it would be cleaner to
have a single helper fxn that most-restrictive union of all attached
device's dma_parms.  Really this should include dma_mask and
coherent_dma_mask, I think.  But that touches a lot of other places in
the code.  If no one objects to the cleanup of moving
dma_mask/coherent_dma_mask into dma_parms, I'll do this first.

So anyways, don't consider this patch yet for inclusion, I'll make an
updated one based on dma_parms..

Hi Rob,
Any news on this patch-set?

BR,
-R

BR,
~Sumit.

On Thu, Jul 19, 2012 at 11:23 AM, Rob Clark [off-list ref] wrote:

quoted

From: Rob Clark <redacted>

Add some helpers to iterate through all attachers and get the most
restrictive segment size/count/boundary.

Signed-off-by: Rob Clark <redacted>
---
 drivers/base/dma-buf.c  |   63 +++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/dma-buf.h |   19 ++++++++++++++
 2 files changed, 82 insertions(+)

diff --git a/drivers/base/dma-buf.c b/drivers/base/dma-buf.c
index 24e88fe..757ee20 100644
--- a/drivers/base/dma-buf.c
+++ b/drivers/base/dma-buf.c

@@ -192,6 +192,69 @@ void dma_buf_put(struct dma_buf *dmabuf)
 EXPORT_SYMBOL_GPL(dma_buf_put);

 /**
+ * dma_buf_max_seg_size - helper for exporters to get the minimum of
+ * all attached device's max segment size
+ */
+unsigned int dma_buf_max_seg_size(struct dma_buf *dmabuf)
+{
+       struct dma_buf_attachment *attach;
+       unsigned int max = (unsigned int)-1;
+
+       if (WARN_ON(!dmabuf))
+               return 0;
+
+       mutex_lock(&dmabuf->lock);
+       list_for_each_entry(attach, &dmabuf->attachments, node)
+               max = min(max, dma_get_max_seg_size(attach->dev));
+       mutex_unlock(&dmabuf->lock);
+
+       return max;
+}
+EXPORT_SYMBOL_GPL(dma_buf_max_seg_size);
+
+/**
+ * dma_buf_max_seg_count - helper for exporters to get the minimum of
+ * all attached device's max segment count
+ */
+unsigned int dma_buf_max_seg_count(struct dma_buf *dmabuf)
+{
+       struct dma_buf_attachment *attach;
+       unsigned int max = (unsigned int)-1;
+
+       if (WARN_ON(!dmabuf))
+               return 0;
+
+       mutex_lock(&dmabuf->lock);
+       list_for_each_entry(attach, &dmabuf->attachments, node)
+               max = min(max, dma_get_max_seg_count(attach->dev));
+       mutex_unlock(&dmabuf->lock);
+
+       return max;
+}
+EXPORT_SYMBOL_GPL(dma_buf_max_seg_count);
+
+/**
+ * dma_buf_get_seg_boundary - helper for exporters to get the most
+ * restrictive segment alignment of all the attached devices
+ */
+unsigned int dma_buf_get_seg_boundary(struct dma_buf *dmabuf)
+{
+       struct dma_buf_attachment *attach;
+       unsigned int mask = (unsigned int)-1;
+
+       if (WARN_ON(!dmabuf))
+               return 0;
+
+       mutex_lock(&dmabuf->lock);
+       list_for_each_entry(attach, &dmabuf->attachments, node)
+               mask &= dma_get_seg_boundary(attach->dev);
+       mutex_unlock(&dmabuf->lock);
+
+       return mask;
+}
+EXPORT_SYMBOL_GPL(dma_buf_get_seg_boundary);
+
+/**
  * dma_buf_attach - Add the device to dma_buf's attachments list; optionally,
  * calls attach() of dma_buf_ops to allow device-specific attach functionality
  * @dmabuf:    [in]    buffer to attach device to.

diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h
index eb48f38..9533b9b 100644
--- a/include/linux/dma-buf.h
+++ b/include/linux/dma-buf.h

@@ -167,6 +167,10 @@ int dma_buf_fd(struct dma_buf *dmabuf, int flags);
 struct dma_buf *dma_buf_get(int fd);
 void dma_buf_put(struct dma_buf *dmabuf);

+unsigned int dma_buf_max_seg_size(struct dma_buf *dmabuf);
+unsigned int dma_buf_max_seg_count(struct dma_buf *dmabuf);
+unsigned int dma_buf_get_seg_boundary(struct dma_buf *dmabuf);
+
 struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *,
                                        enum dma_data_direction);
 void dma_buf_unmap_attachment(struct dma_buf_attachment *, struct sg_table *,

@@ -220,6 +224,21 @@ static inline void dma_buf_put(struct dma_buf *dmabuf)
        return;
 }

+static inline unsigned int dma_buf_max_seg_size(struct dma_buf *dmabuf)
+{
+       return 0;
+}
+
+static inline unsigned int dma_buf_max_seg_count(struct dma_buf *dmabuf)
+{
+       return 0;
+}
+
+static inline unsigned int dma_buf_get_seg_boundary(struct dma_buf *dmabuf)
+{
+       return 0;
+}
+
 static inline struct sg_table *dma_buf_map_attachment(
        struct dma_buf_attachment *attach, enum dma_data_direction write)
 {
--

1.7.9.5

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