Hi Rob,
On 07/19/2012 06:23 PM, Rob Clark wrote:
From: Rob Clark rob@ti.com
Add some helpers to iterate through all attachers and get the most restrictive segment size/count/boundary.
Signed-off-by: Rob Clark rob@ti.com
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;
Maybe you should change return type to 'int' and return -EINVAL here?
- 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;
maybe return -EINVAL here?
- mutex_lock(&dmabuf->lock);
- list_for_each_entry(attach, &dmabuf->attachments, node)
max = min(max, dma_get_max_seg_count(attach->dev));
I think that there is a bug here. Assume that there are two deices on the list, one using unlimited number of segments (value 0), the second one needs a contiguous buffer (value 1). The result of the function is 0 = min(0, 2).
The return value 0 indicates that the unlimited number of sg segments is accepted what is *wrong* because the correct value should be 1.
I recommend to change the semantics for unlimited number of segments from 'value 0' to:
#define DMA_SEGMENTS_COUNT_UNLIMITED ((unsigned long)INT_MAX)
Using INT_MAX will allow using safe conversions between signed and unsigned integers.
- 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);
Instead of adding an army of new handlers you could provide a single helper:
int dma_buf_get_parameters(struct dma_buf *dmabuf, struct device_dma_parameters *params);
This function will fill *params with lowest common DMA requirements for all devices on attachment list. Return value can be used to diagnose errors like incorrectly initialized dma_buf pointer (like no attachments on an attachment list).
Moreover, there will be no need to add a new handler every time device_dma_parameters is extended.
Regards, Tomasz Stanislawski
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) {