* [PATCH] device: add dma_params->max_segment_count
@ 2012-07-12 17:44 Rob Clark
2012-07-19 11:30 ` [Linaro-mm-sig] " Daniel Vetter
0 siblings, 1 reply; 2+ messages in thread
From: Rob Clark @ 2012-07-12 17:44 UTC (permalink / raw)
To: linux-kernel; +Cc: patches, linaro-mm-sig, Rob Clark
From: Rob Clark <rob@ti.com>
For devices which have constraints about maximum number of segments
in an sglist. For example, a device which could only deal with
contiguous buffers would set max_segment_count to 1.
The initial motivation is for devices sharing buffers via dma-buf,
to allow the buffer exporter to know the constraints of other
devices which have attached to the buffer. The dma_mask and fields
in 'struct device_dma_parameters' tell the exporter everything else
that is needed, except whether the importer has constraints about
maximum number of segments.
Signed-off-by: Rob Clark <rob@ti.com>
---
include/linux/device.h | 1 +
include/linux/dma-mapping.h | 16 ++++++++++++++++
2 files changed, 17 insertions(+)
diff --git a/include/linux/device.h b/include/linux/device.h
index 161d962..3813735 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -568,6 +568,7 @@ struct device_dma_parameters {
* sg limitations.
*/
unsigned int max_segment_size;
+ unsigned int max_segment_count; /* zero for unlimited */
unsigned long segment_boundary_mask;
};
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index dfc099e..f380f79 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -111,6 +111,22 @@ static inline unsigned int dma_set_max_seg_size(struct device *dev,
return -EIO;
}
+static inline unsigned int dma_get_max_seg_count(struct device *dev)
+{
+ return dev->dma_parms ? dev->dma_parms->max_segment_count : 0;
+}
+
+static inline int dma_set_max_seg_count(struct device *dev,
+ unsigned int count)
+{
+ if (dev->dma_parms) {
+ dev->dma_parms->max_segment_count = count;
+ return 0;
+ } else
+ return -EIO;
+}
+
+
static inline unsigned long dma_get_seg_boundary(struct device *dev)
{
return dev->dma_parms ?
--
1.7.9.5
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [Linaro-mm-sig] [PATCH] device: add dma_params->max_segment_count
2012-07-12 17:44 [PATCH] device: add dma_params->max_segment_count Rob Clark
@ 2012-07-19 11:30 ` Daniel Vetter
0 siblings, 0 replies; 2+ messages in thread
From: Daniel Vetter @ 2012-07-19 11:30 UTC (permalink / raw)
To: Rob Clark; +Cc: linux-kernel, linaro-mm-sig
On Thu, Jul 12, 2012 at 12:44:16PM -0500, Rob Clark wrote:
> From: Rob Clark <rob@ti.com>
>
> For devices which have constraints about maximum number of segments
> in an sglist. For example, a device which could only deal with
> contiguous buffers would set max_segment_count to 1.
>
> The initial motivation is for devices sharing buffers via dma-buf,
> to allow the buffer exporter to know the constraints of other
> devices which have attached to the buffer. The dma_mask and fields
> in 'struct device_dma_parameters' tell the exporter everything else
> that is needed, except whether the importer has constraints about
> maximum number of segments.
>
> Signed-off-by: Rob Clark <rob@ti.com>
I like this and I guess it's an easy way to solve most of our sharing
issues with funnier hw. Exporters can then fall back to large allocations,
CMA, special-purpose remappes (like the omap tiler) or platform-specific
carveout areas (stolen mem for drm/i915). One little thing though:
Could you add a little helper (maybe in a second patch) to dma_buf that
walks all currently attached buffers and ORs together all masks and takes
the minimum of all other limits for all attached buffers?
Yours, Daniel
> ---
> include/linux/device.h | 1 +
> include/linux/dma-mapping.h | 16 ++++++++++++++++
> 2 files changed, 17 insertions(+)
>
> diff --git a/include/linux/device.h b/include/linux/device.h
> index 161d962..3813735 100644
> --- a/include/linux/device.h
> +++ b/include/linux/device.h
> @@ -568,6 +568,7 @@ struct device_dma_parameters {
> * sg limitations.
> */
> unsigned int max_segment_size;
> + unsigned int max_segment_count; /* zero for unlimited */
> unsigned long segment_boundary_mask;
> };
>
> diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
> index dfc099e..f380f79 100644
> --- a/include/linux/dma-mapping.h
> +++ b/include/linux/dma-mapping.h
> @@ -111,6 +111,22 @@ static inline unsigned int dma_set_max_seg_size(struct device *dev,
> return -EIO;
> }
>
> +static inline unsigned int dma_get_max_seg_count(struct device *dev)
> +{
> + return dev->dma_parms ? dev->dma_parms->max_segment_count : 0;
> +}
> +
> +static inline int dma_set_max_seg_count(struct device *dev,
> + unsigned int count)
> +{
> + if (dev->dma_parms) {
> + dev->dma_parms->max_segment_count = count;
> + return 0;
> + } else
> + return -EIO;
> +}
> +
> +
> static inline unsigned long dma_get_seg_boundary(struct device *dev)
> {
> return dev->dma_parms ?
> --
> 1.7.9.5
>
>
> _______________________________________________
> Linaro-mm-sig mailing list
> Linaro-mm-sig@lists.linaro.org
> http://lists.linaro.org/mailman/listinfo/linaro-mm-sig
--
Daniel Vetter
Mail: daniel@ffwll.ch
Mobile: +41 (0)79 365 57 48
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