[RFC: DMA_PMD 10/22] driver core: Add per-device dma_pmd_* sysfs attributes

[Luigi Rizzo]

Add four boolean attributes to struct device exposed under
/sys/devices/*/*/dma_pmd_*:
  - dma_pmd_rxbuf:   enable DMA_PMD pools for RX buffers / page_pool
  - dma_pmd_tx_hdrs: enable DMA_PMD pools for TX header bounce buffers
  - dma_pmd_rings:   enable DMA_PMD arena for coherent rings
  - dma_pmd_debug:   log coherent DMA alloc timing and arena usage

These can be used by device drivers to selectively enable DMA_PMD for
their allocations.

Signed-off-by: Luigi Rizzo <lrizzo@xxxxxxxxxx>
---
 drivers/base/core.c    | 51 ++++++++++++++++++++++++++++++++++++++++++
 include/linux/device.h |  5 +++++
 2 files changed, 56 insertions(+)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 4c0c373998a19..f8c3c42d84b8d 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -2905,6 +2905,43 @@ static ssize_t removable_show(struct device *dev, const struct device_attribute
 }
 static const DEVICE_ATTR_RO(removable);
 
+/* Per-device configuration to selectively enable DMA_PMD */
+#define DMA_PMD_BOOL_ATTR(name)						\
+static ssize_t name##_show(struct device *dev,				\
+			   struct device_attribute *attr, char *buf)	\
+{									\
+	return sysfs_emit(buf, "%u\n", READ_ONCE(dev->name));		\
+}									\
+static ssize_t name##_store(struct device *dev,				\
+			    struct device_attribute *attr,		\
+			    const char *buf, size_t count)		\
+{									\
+	bool val;							\
+	int ret = kstrtobool(buf, &val);				\
+	if (ret < 0)							\
+		return ret;						\
+	WRITE_ONCE(dev->name, val);					\
+	return count;							\
+}									\
+static DEVICE_ATTR_RW(name)
+
+DMA_PMD_BOOL_ATTR(dma_pmd_rxbuf);
+DMA_PMD_BOOL_ATTR(dma_pmd_tx_hdrs);
+DMA_PMD_BOOL_ATTR(dma_pmd_rings);
+DMA_PMD_BOOL_ATTR(dma_pmd_debug);
+
+static struct attribute *dev_attr_dma_pmd[] = {
+	&dev_attr_dma_pmd_rxbuf.attr,
+	&dev_attr_dma_pmd_tx_hdrs.attr,
+	&dev_attr_dma_pmd_rings.attr,
+	&dev_attr_dma_pmd_debug.attr,
+	NULL,
+};
+
+static const struct attribute_group dev_attr_dma_pmd_group = {
+	.attrs = dev_attr_dma_pmd,
+};
+
 int device_add_groups(struct device *dev,
 		      const struct attribute_group *const *groups)
 {
@@ -3012,8 +3049,20 @@ static int device_add_attrs(struct device *dev)
 			goto err_remove_dev_removable;
 	}
 
+	if (dev->dma_mask) {
+		error = device_add_group(dev, &dev_attr_dma_pmd_group);
+		if (error)
+			goto err_remove_dev_physical_location;
+	}
+
 	return 0;
 
+ err_remove_dev_physical_location:
+	if (dev->physical_location) {
+		device_remove_group(dev, &dev_attr_physical_location_group);
+		kfree(dev->physical_location);
+		dev->physical_location = NULL;
+	}
  err_remove_dev_removable:
 	device_remove_file(dev, &dev_attr_removable);
  err_remove_dev_waiting_for_supplier:
@@ -3037,6 +3086,8 @@ static void device_remove_attrs(struct device *dev)
 	const struct class *class = dev->class;
 	const struct device_type *type = dev->type;
 
+	device_remove_group(dev, &dev_attr_dma_pmd_group);
+
 	if (dev->physical_location) {
 		device_remove_group(dev, &dev_attr_physical_location_group);
 		kfree(dev->physical_location);
diff --git a/include/linux/device.h b/include/linux/device.h
index aee79fd6b32b4..52aa4a7e1cc45 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -794,6 +794,11 @@ struct device {
 
 	enum device_removable	removable;
 
+	bool			dma_pmd_rxbuf;
+	bool			dma_pmd_tx_hdrs;
+	bool			dma_pmd_rings;
+	bool			dma_pmd_debug;
+
 	DECLARE_BITMAP(flags, DEV_FLAG_COUNT);
 };
 
-- 
2.56.0.rc1.315.gc6ed9934b7-goog