[PATCH v1 1/5] dmaengine: add support for custom per-channel sysfs attributes

[Logan Gunthorpe <logang@deltatee.com>]

Add specific support for adding sysfs attributes to channels.

This will be used to replace similar functionality in ioat so it can
be used in other drivers.

Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
---
 drivers/dma/dmaengine.c   | 62 +++++++++++++++++++++++++++++++++++++++
 drivers/dma/dmaengine.h   | 11 +++++++
 include/linux/dmaengine.h |  3 ++
 3 files changed, 76 insertions(+)

diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
index 9049171df857..7ea2a8709c07 100644
--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c
@@ -125,6 +125,63 @@ static int dmaengine_summary_show(struct seq_file *s, void *data)
 }
 DEFINE_SHOW_ATTRIBUTE(dmaengine_summary);
 
+static ssize_t
+dma_chan_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
+{
+	const struct dma_chan_sysfs_entry *entry;
+	struct dma_chan *dma_chan;
+
+	entry = container_of_const(attr, struct dma_chan_sysfs_entry, attr);
+	dma_chan = container_of(kobj, struct dma_chan, kobj);
+
+	if (!entry->show)
+		return -EIO;
+
+	return entry->show(dma_chan, page);
+}
+
+static ssize_t
+dma_chan_attr_store(struct kobject *kobj, struct attribute *attr,
+		    const char *page, size_t count)
+{
+	const struct dma_chan_sysfs_entry *entry;
+	struct dma_chan *dma_chan;
+
+	entry = container_of_const(attr, struct dma_chan_sysfs_entry, attr);
+	dma_chan = container_of(kobj, struct dma_chan, kobj);
+
+	if (!entry->store)
+		return -EIO;
+
+	return entry->store(dma_chan, page, count);
+}
+
+const struct sysfs_ops dma_chan_sysfs_ops = {
+	.show = dma_chan_attr_show,
+	.store = dma_chan_attr_store,
+};
+EXPORT_SYMBOL_GPL(dma_chan_sysfs_ops);
+
+void dma_chan_kobject_add(struct dma_device *dev, const struct kobj_type *type,
+			  const char *name)
+{
+	struct dma_chan *chan;
+	int err;
+
+	list_for_each_entry(chan, &dev->channels, device_node) {
+		chan->kobj_used = true;
+		err = kobject_init_and_add(&chan->kobj, type,
+					   &chan->dev->device.kobj, name);
+		if (err) {
+			dev_warn(dev->dev,
+				 "sysis init error(%d), continuinng...\n", err);
+			kobject_put(&chan->kobj);
+			chan->kobj_used = false;
+		}
+	}
+}
+EXPORT_SYMBOL_GPL(dma_chan_kobject_add);
+
 static void __init dmaengine_debugfs_init(void)
 {
 	rootdir = debugfs_create_dir("dmaengine", NULL);
@@ -1143,6 +1200,11 @@ static void __dma_async_device_channel_unregister(struct dma_device *device,
 	if (chan->local == NULL)
 		return;
 
+	if (chan->kobj_used) {
+		kobject_del(&chan->kobj);
+		kobject_put(&chan->kobj);
+	}
+
 	WARN_ONCE(!device->device_release && chan->client_count,
 		  "%s called while %d clients hold a reference\n",
 		  __func__, chan->client_count);
diff --git a/drivers/dma/dmaengine.h b/drivers/dma/dmaengine.h
index 53f16d3f0029..496cac056350 100644
--- a/drivers/dma/dmaengine.h
+++ b/drivers/dma/dmaengine.h
@@ -182,6 +182,17 @@ dmaengine_desc_callback_valid(struct dmaengine_desc_callback *cb)
 struct dma_chan *dma_get_slave_channel(struct dma_chan *chan);
 struct dma_chan *dma_get_any_slave_channel(struct dma_device *device);
 
+struct dma_chan_sysfs_entry {
+	struct attribute attr;
+	ssize_t (*show)(struct dma_chan *chan, char *page);
+	ssize_t (*store)(struct dma_chan *chan, const char *page, size_t count);
+};
+
+extern const struct sysfs_ops dma_chan_sysfs_ops;
+
+void dma_chan_kobject_add(struct dma_device *dev, const struct kobj_type *type,
+			  const char *name);
+
 #ifdef CONFIG_DEBUG_FS
 #include <linux/debugfs.h>
 
diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index b3d251c9734e..852943ef46b8 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -358,6 +358,9 @@ struct dma_chan {
 	struct dma_router *router;
 	void *route_data;
 
+	bool kobj_used;
+	struct kobject kobj;
+
 	void *private;
 };
 
-- 
2.47.3