Re: [V3 PATCH 3/5] device property: Introduces device_dma_is_coherent()

From: santosh shilimkar
Date: Fri May 08 2015 - 16:37:11 EST

On 5/8/2015 1:58 PM, Rafael J. Wysocki wrote:
On Friday, May 08, 2015 01:27:00 PM santosh shilimkar wrote:
On 5/8/2015 1:49 PM, Rafael J. Wysocki wrote:
On Thursday, May 07, 2015 09:12:00 PM santosh.shilimkar@xxxxxxxxxx wrote:
On 5/7/15 5:37 PM, Suravee Suthikulpanit wrote:
Currently, device drivers, which support both OF and ACPI,
need to call two separate APIs, of_dma_is_coherent() and
acpi_dma_is_coherent()) to determine device coherency attribute.

This patch simplifies this process by introducing a new device
property API, device_dma_is_coherent(), which calls the appropriate
interface based on the booting architecture.

Signed-off-by: Suravee Suthikulpanit <Suravee.Suthikulpanit@xxxxxxx>
drivers/base/property.c | 12 ++++++++++++
include/linux/property.h | 2 ++
2 files changed, 14 insertions(+)

diff --git a/drivers/base/property.c b/drivers/base/property.c
index 1d0b116..8123c6e 100644
--- a/drivers/base/property.c
+++ b/drivers/base/property.c
@@ -14,6 +14,7 @@
#include <linux/export.h>
#include <linux/kernel.h>
#include <linux/of.h>
+#include <linux/of_address.h>
#include <linux/property.h>

@@ -519,3 +520,14 @@ unsigned int device_get_child_node_count(struct device *dev)
return count;
+bool device_dma_is_coherent(struct device *dev)
+ if (IS_ENABLED(CONFIG_OF) && dev->of_node)

Do you really need that IS_ENABLED(CONFIG_OF) ?
In other words, dev->of_node should be null for !CONFIG_OF

Yes, but IS_ENABLED(CONFIG_OF) causes the check to be optimized away by the
compiler if CONFIG_OF is not enabled.

Sure but my point was why you need it when just 'dev->of_node' check
is enough. May be I missed something.

dev->of_node is present when CONFIG_OF is not enabled too. Without the
IS_ENABLED(CONFIG_OF) this becomes a pointless pointer check that will
always evaluate to 'false' on systems without CONFIG_OF, AFAICS.

Got it now. Thanks for expanding it.

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at