dmaengine: add a release for dma class devices and dependent infrastructure

Resolves:
WARNING: at drivers/base/core.c:122 device_release+0x4d/0x52()
Device 'dma0chan0' does not have a release() function, it is broken and must be fixed.

The dma_chan_dev object is introduced to gear-match sysfs kobject and
dmaengine channel lifetimes.  When a channel is removed access to the
sysfs entries return -ENODEV until the kobject can be released.

The bulk of the change is updates to existing code to handle the extra
layer of indirection between a dma_chan and its struct device.

Reported-by: Alexander Beregalov <a.beregalov@gmail.com>
Acked-by: Stephen Hemminger <shemminger@vyatta.com>
Cc: Haavard Skinnemoen <haavard.skinnemoen@atmel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 16 insertions, 3 deletions

diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index 1419a5094478..d6b6bff355f4 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -113,7 +113,7 @@ struct dma_chan_percpu {
  * @device: ptr to the dma device who supplies this channel, always !%NULL
  * @cookie: last cookie value returned to client
  * @chan_id: channel ID for sysfs
- * @class_dev: class device for sysfs
+ * @dev: class device for sysfs
  * @refcount: kref, used in "bigref" slow-mode
  * @slow_ref: indicates that the DMA channel is free
  * @rcu: the DMA channel's RCU head
@@ -128,7 +128,7 @@ struct dma_chan {
 
         /* sysfs */
         int chan_id;
-        struct device dev;
+        struct dma_chan_dev *dev;
 
         struct list_head device_node;
         struct dma_chan_percpu *local;
@@ -136,7 +136,20 @@ struct dma_chan {
         int table_count;
 };
 
-#define to_dma_chan(p) container_of(p, struct dma_chan, dev)
+/**
+ * struct dma_chan_dev - relate sysfs device node to backing channel device
+ * @chan - driver channel device
+ * @device - sysfs device
+ */
+struct dma_chan_dev {
+        struct dma_chan *chan;
+        struct device device;
+};
+
+static inline const char *dma_chan_name(struct dma_chan *chan)
+{
+        return dev_name(&chan->dev->device);
+}
 
 void dma_chan_cleanup(struct kref *kref);