v4l2-device: allow a NULL parent device when registering.

From: Hans Verkuil <hverkuil@xs4all.nl>

Some drivers (e.g. for ISA devices) have no parent device because there
is no associated bus driver. Allow the parent device to be NULL in
those cases when registering v4l2_device.

Priority: normal

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>

3 files changed, 72 insertions, 54 deletions

diff --git a/linux/Documentation/video4linux/v4l2-framework.txt b/linux/Documentation/video4linux/v4l2-framework.txt
index a6005257a..e1620e2a3 100644
--- a/linux/Documentation/video4linux/v4l2-framework.txt
+++ b/linux/Documentation/video4linux/v4l2-framework.txt
@@ -84,12 +84,14 @@ You must register the device instance:
 	v4l2_device_register(struct device *dev, struct v4l2_device *v4l2_dev);
 
 Registration will initialize the v4l2_device struct and link dev->driver_data
-to v4l2_dev. Registration will also set v4l2_dev->name to a value derived from
-dev (driver name followed by the bus_id, to be precise). You may change the
-name after registration if you want.
+to v4l2_dev. If v4l2_dev->name is empty then it will be set to a value derived
+from dev (driver name followed by the bus_id, to be precise). If you set it
+up before calling v4l2_device_register then it will be untouched. If dev is
+NULL, then you *must* setup v4l2_dev->name before calling v4l2_device_register.
 
 The first 'dev' argument is normally the struct device pointer of a pci_dev,
-usb_device or platform_device.
+usb_device or platform_device. It is rare for dev to be NULL, but it happens
+with ISA devices, for example.
 
 You unregister with:
 
@@ -531,11 +533,11 @@ struct v4l2_device *v4l2_dev = vdev->v4l2_dev;
 video buffer helper functions
 -----------------------------
 
-The v4l2 core API provides a standard method for dealing with video 
-buffers. Those methods allow a driver to implement read(), mmap() and 
+The v4l2 core API provides a standard method for dealing with video
+buffers. Those methods allow a driver to implement read(), mmap() and
 overlay() on a consistent way.
 
-There are currently methods for using video buffers on devices that 
+There are currently methods for using video buffers on devices that
 supports DMA with scatter/gather method (videobuf-dma-sg), DMA with
 linear access (videobuf-dma-contig), and vmalloced buffers, mostly
 used on USB drivers (videobuf-vmalloc).
@@ -544,50 +546,50 @@ Any driver using videobuf should provide operations (callbacks) for
 four handlers:
 
 ops->buf_setup   - calculates the size of the video buffers and avoid they
-		   to waste more than some maximum limit of RAM; 
+		   to waste more than some maximum limit of RAM;
 ops->buf_prepare - fills the video buffer structs and calls
 		   videobuf_iolock() to alloc and prepare mmaped memory;
 ops->buf_queue   - advices the driver that another buffer were
-		   requested (by read() or by QBUF); 
+		   requested (by read() or by QBUF);
 ops->buf_release - frees any buffer that were allocated.
 
 In order to use it, the driver need to have a code (generally called at
 interrupt context) that will properly handle the buffer request lists,
 announcing that a new buffer were filled.
 
-The irq handling code should handle the videobuf task lists, in order 
-to advice videobuf that a new frame were filled, in order to honor to a 
+The irq handling code should handle the videobuf task lists, in order
+to advice videobuf that a new frame were filled, in order to honor to a
 request. The code is generally like this one:
-        if (list_empty(&dma_q->active))
+	if (list_empty(&dma_q->active))
 		return;
 
-        buf = list_entry(dma_q->active.next, struct vbuffer, vb.queue);
+	buf = list_entry(dma_q->active.next, struct vbuffer, vb.queue);
 
-        if (!waitqueue_active(&buf->vb.done))
+	if (!waitqueue_active(&buf->vb.done))
 		return;
 
 	/* Some logic to handle the buf may be needed here */
 
-        list_del(&buf->vb.queue);
-        do_gettimeofday(&buf->vb.ts);
-        wake_up(&buf->vb.done);
+	list_del(&buf->vb.queue);
+	do_gettimeofday(&buf->vb.ts);
+	wake_up(&buf->vb.done);
 
-Those are the videobuffer functions used on drivers, implemented on 
+Those are the videobuffer functions used on drivers, implemented on
 videobuf-core:
 
 - Videobuf init functions
   videobuf_queue_sg_init()
-      Initializes the videobuf infrastructure. This function should be 
-      called before any other videobuf function on drivers that uses DMA 
+      Initializes the videobuf infrastructure. This function should be
+      called before any other videobuf function on drivers that uses DMA
       Scatter/Gather buffers.
 
   videobuf_queue_dma_contig_init
-      Initializes the videobuf infrastructure. This function should be 
-      called before any other videobuf function on drivers that need DMA 
+      Initializes the videobuf infrastructure. This function should be
+      called before any other videobuf function on drivers that need DMA
       contiguous buffers.
 
   videobuf_queue_vmalloc_init()
-      Initializes the videobuf infrastructure. This function should be 
+      Initializes the videobuf infrastructure. This function should be
       called before any other videobuf function on USB (and other drivers)
       that need a vmalloced type of videobuf.
 
@@ -607,12 +609,12 @@ videobuf-core:
   Stops video handling, ends mmap and frees mmap and other buffers.
 
 - V4L2 api functions. Those functions correspond to VIDIOC_foo ioctls:
-   videobuf_reqbufs(), videobuf_querybuf(), videobuf_qbuf(), 
+   videobuf_reqbufs(), videobuf_querybuf(), videobuf_qbuf(),
    videobuf_dqbuf(), videobuf_streamon(), videobuf_streamoff().
 
 - V4L1 api function (corresponds to VIDIOCMBUF ioctl):
    videobuf_cgmbuf()
-      This function is used to provide backward compatibility with V4L1 
+      This function is used to provide backward compatibility with V4L1
       API.
 
 - Some help functions for read()/poll() operations:
@@ -623,7 +625,7 @@ videobuf-core:
    videobuf_poll_stream()
       polling help function
 
-The better way to understand it is to take a look at vivi driver. One 
-of the main reasons for vivi is to be a videobuf usage example. the 
-vivi_thread_tick() does the task that the IRQ callback would do on PCI 
+The better way to understand it is to take a look at vivi driver. One
+of the main reasons for vivi is to be a videobuf usage example. the
+vivi_thread_tick() does the task that the IRQ callback would do on PCI
 drivers (or the irq callback on USB).
diff --git a/linux/drivers/media/video/v4l2-device.c b/linux/drivers/media/video/v4l2-device.c
index e84925976..cb8234437 100644
--- a/linux/drivers/media/video/v4l2-device.c
+++ b/linux/drivers/media/video/v4l2-device.c
@@ -27,15 +27,24 @@
 
 int v4l2_device_register(struct device *dev, struct v4l2_device *v4l2_dev)
 {
-	if (dev == NULL || v4l2_dev == NULL)
+	if (v4l2_dev == NULL)
 		return -EINVAL;
-	/* Warn if we apparently re-register a device */
-	WARN_ON(dev_get_drvdata(dev) != NULL);
+
 	INIT_LIST_HEAD(&v4l2_dev->subdevs);
 	spin_lock_init(&v4l2_dev->lock);
 	v4l2_dev->dev = dev;
-	snprintf(v4l2_dev->name, sizeof(v4l2_dev->name), "%s %s",
+	if (dev == NULL) {
+		/* If dev == NULL, then name must be filled in by the caller */
+		WARN_ON(!v4l2_dev->name[0]);
+		return 0;
+	}
+
+	/* Set name to driver name + device name if it is empty. */
+	if (!v4l2_dev->name[0])
+		snprintf(v4l2_dev->name, sizeof(v4l2_dev->name), "%s %s",
 			dev->driver->name, dev_name(dev));
+	if (dev_get_drvdata(dev))
+		v4l2_warn(v4l2_dev, "Non-NULL drvdata on register\n");
 	dev_set_drvdata(dev, v4l2_dev);
 	return 0;
 }
@@ -45,10 +54,11 @@ void v4l2_device_unregister(struct v4l2_device *v4l2_dev)
 {
 	struct v4l2_subdev *sd, *next;
 
-	if (v4l2_dev == NULL || v4l2_dev->dev == NULL)
+	if (v4l2_dev == NULL)
 		return;
-	dev_set_drvdata(v4l2_dev->dev, NULL);
-	/* unregister subdevs */
+	if (v4l2_dev->dev)
+		dev_set_drvdata(v4l2_dev->dev, NULL);
+	/* Unregister subdevs */
 	list_for_each_entry_safe(sd, next, &v4l2_dev->subdevs, list)
 		v4l2_device_unregister_subdev(sd);
 
@@ -56,19 +66,20 @@ void v4l2_device_unregister(struct v4l2_device *v4l2_dev)
 }
 EXPORT_SYMBOL_GPL(v4l2_device_unregister);
 
-int v4l2_device_register_subdev(struct v4l2_device *dev, struct v4l2_subdev *sd)
+int v4l2_device_register_subdev(struct v4l2_device *v4l2_dev,
+						struct v4l2_subdev *sd)
 {
 	/* Check for valid input */
-	if (dev == NULL || sd == NULL || !sd->name[0])
+	if (v4l2_dev == NULL || sd == NULL || !sd->name[0])
 		return -EINVAL;
 	/* Warn if we apparently re-register a subdev */
 	WARN_ON(sd->dev != NULL);
 	if (!try_module_get(sd->owner))
 		return -ENODEV;
-	sd->dev = dev;
-	spin_lock(&dev->lock);
-	list_add_tail(&sd->list, &dev->subdevs);
-	spin_unlock(&dev->lock);
+	sd->dev = v4l2_dev;
+	spin_lock(&v4l2_dev->lock);
+	list_add_tail(&sd->list, &v4l2_dev->subdevs);
+	spin_unlock(&v4l2_dev->lock);
 	return 0;
 }
 EXPORT_SYMBOL_GPL(v4l2_device_register_subdev);
diff --git a/linux/include/media/v4l2-device.h b/linux/include/media/v4l2-device.h
index 55e41afd9..5d7146dc2 100644
--- a/linux/include/media/v4l2-device.h
+++ b/linux/include/media/v4l2-device.h
@@ -33,7 +33,9 @@
 #define V4L2_DEVICE_NAME_SIZE (BUS_ID_SIZE + 16)
 
 struct v4l2_device {
-	/* dev->driver_data points to this struct */
+	/* dev->driver_data points to this struct.
+	   Note: dev might be NULL if there is no parent device
+	   as is the case with e.g. ISA devices. */
 	struct device *dev;
 	/* used to keep track of the registered subdevs */
 	struct list_head subdevs;
@@ -44,7 +46,9 @@ struct v4l2_device {
 	char name[V4L2_DEVICE_NAME_SIZE];
 };
 
-/* Initialize v4l2_dev and make dev->driver_data point to v4l2_dev */
+/* Initialize v4l2_dev and make dev->driver_data point to v4l2_dev.
+   dev may be NULL in rare cases (ISA devices). In that case you
+   must fill in the v4l2_dev->name field before calling this function. */
 int __must_check v4l2_device_register(struct device *dev, struct v4l2_device *v4l2_dev);
 /* Set v4l2_dev->dev->driver_data to NULL and unregister all sub-devices */
 void v4l2_device_unregister(struct v4l2_device *v4l2_dev);
@@ -52,23 +56,24 @@ void v4l2_device_unregister(struct v4l2_device *v4l2_dev);
 /* Register a subdev with a v4l2 device. While registered the subdev module
    is marked as in-use. An error is returned if the module is no longer
    loaded when you attempt to register it. */
-int __must_check v4l2_device_register_subdev(struct v4l2_device *dev, struct v4l2_subdev *sd);
+int __must_check v4l2_device_register_subdev(struct v4l2_device *v4l2_dev,
+						struct v4l2_subdev *sd);
 /* Unregister a subdev with a v4l2 device. Can also be called if the subdev
    wasn't registered. In that case it will do nothing. */
 void v4l2_device_unregister_subdev(struct v4l2_subdev *sd);
 
 /* Iterate over all subdevs. */
-#define v4l2_device_for_each_subdev(sd, dev)				\
-	list_for_each_entry(sd, &(dev)->subdevs, list)
+#define v4l2_device_for_each_subdev(sd, v4l2_dev)			\
+	list_for_each_entry(sd, &(v4l2_dev)->subdevs, list)
 
 /* Call the specified callback for all subdevs matching the condition.
    Ignore any errors. Note that you cannot add or delete a subdev
    while walking the subdevs list. */
-#define __v4l2_device_call_subdevs(dev, cond, o, f, args...) 		\
+#define __v4l2_device_call_subdevs(v4l2_dev, cond, o, f, args...) 	\
 	do { 								\
 		struct v4l2_subdev *sd; 				\
 									\
-		list_for_each_entry(sd, &(dev)->subdevs, list)   	\
+		list_for_each_entry(sd, &(v4l2_dev)->subdevs, list)   	\
 			if ((cond) && sd->ops->o && sd->ops->o->f) 	\
 				sd->ops->o->f(sd , ##args); 		\
 	} while (0)
@@ -77,12 +82,12 @@ void v4l2_device_unregister_subdev(struct v4l2_subdev *sd);
    If the callback returns an error other than 0 or -ENOIOCTLCMD, then
    return with that error code. Note that you cannot add or delete a
    subdev while walking the subdevs list. */
-#define __v4l2_device_call_subdevs_until_err(dev, cond, o, f, args...)  \
+#define __v4l2_device_call_subdevs_until_err(v4l2_dev, cond, o, f, args...) \
 ({ 									\
 	struct v4l2_subdev *sd; 					\
 	long err = 0; 							\
 									\
-	list_for_each_entry(sd, &(dev)->subdevs, list) { 		\
+	list_for_each_entry(sd, &(v4l2_dev)->subdevs, list) { 		\
 		if ((cond) && sd->ops->o && sd->ops->o->f) 		\
 			err = sd->ops->o->f(sd , ##args); 		\
 		if (err && err != -ENOIOCTLCMD)				\
@@ -94,16 +99,16 @@ void v4l2_device_unregister_subdev(struct v4l2_subdev *sd);
 /* Call the specified callback for all subdevs matching grp_id (if 0, then
    match them all). Ignore any errors. Note that you cannot add or delete
    a subdev while walking the subdevs list. */
-#define v4l2_device_call_all(dev, grpid, o, f, args...) 		\
-	__v4l2_device_call_subdevs(dev, 				\
+#define v4l2_device_call_all(v4l2_dev, grpid, o, f, args...) 		\
+	__v4l2_device_call_subdevs(v4l2_dev, 				\
 			!(grpid) || sd->grp_id == (grpid), o, f , ##args)
 
 /* Call the specified callback for all subdevs matching grp_id (if 0, then
    match them all). If the callback returns an error other than 0 or
    -ENOIOCTLCMD, then return with that error code. Note that you cannot
    add or delete a subdev while walking the subdevs list. */
-#define v4l2_device_call_until_err(dev, grpid, o, f, args...) 		\
-	__v4l2_device_call_subdevs_until_err(dev,			\
+#define v4l2_device_call_until_err(v4l2_dev, grpid, o, f, args...) 	\
+	__v4l2_device_call_subdevs_until_err(v4l2_dev,			\
 		       !(grpid) || sd->grp_id == (grpid), o, f , ##args)
 
 #endif