staging: comedi: change comedi_read/write_subdevice() parameters

`comedi_read_subdevice()` and `comedi_write_subdevice()` currently take
a single parameter pointing to a `struct comedi_file_info`.  I'm trying
to get rid of `struct comedi_file_info` so as part of that plan,
`comedi_read_subdevice()` and `comedi_write_subdevice()` need to change.
Change them to take two parameters: a pointer to a `struct
comedi_device` and a minor device number.  If the minor device number is
a "board" minor device number (`minor < COMEDI_NUM_BOARD_MINORS`) we'll
always return the default read or write subdevice.  If the minor device
number if a "subdevice" minor device number a different read or write
subdevice may be returned.  In that case, use the subdevice minor device
number to look up the information about whether the default read or
write subdevice needs to be overridden.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Reviewed-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/comedi_fops.c

@@ -211,23 +211,33 @@ struct comedi_device *comedi_dev_from_minor(unsigned minor)
 EXPORT_SYMBOL_GPL(comedi_dev_from_minor);
 
 static struct comedi_subdevice *
-comedi_read_subdevice(const struct comedi_file_info *info)
+comedi_read_subdevice(const struct comedi_device *dev, unsigned int minor)
 {
-	if (info->read_subdevice)
-		return info->read_subdevice;
-	if (info->device)
-		return info->device->read_subdev;
-	return NULL;
+	struct comedi_file_info *info;
+
+	if (minor >= COMEDI_NUM_BOARD_MINORS) {
+		info = comedi_file_info_from_subdevice_minor(minor);
+		if (!info || info->device != dev)
+			return NULL;
+		if (info->read_subdevice)
+			return info->read_subdevice;
+	}
+	return dev->read_subdev;
 }
 
 static struct comedi_subdevice *
-comedi_write_subdevice(const struct comedi_file_info *info)
+comedi_write_subdevice(const struct comedi_device *dev, unsigned int minor)
 {
-	if (info->write_subdevice)
-		return info->write_subdevice;
-	if (info->device)
-		return info->device->write_subdev;
-	return NULL;
+	struct comedi_file_info *info;
+
+	if (minor >= COMEDI_NUM_BOARD_MINORS) {
+		info = comedi_file_info_from_subdevice_minor(minor);
+		if (!info || info->device != dev)
+			return NULL;
+		if (info->write_subdevice)
+			return info->write_subdevice;
+	}
+	return dev->write_subdev;
 }
 
 static int resize_async_buffer(struct comedi_device *dev,
@@ -287,7 +297,7 @@ static ssize_t show_max_read_buffer_kb(struct device *csdev,
 
 	dev = info->device;
 	mutex_lock(&dev->mutex);
-	s = comedi_read_subdevice(info);
+	s = comedi_read_subdevice(dev, minor);
 	if (s && (s->subdev_flags & SDF_CMD_READ) && s->async)
 		size = s->async->max_bufsize / 1024;
 	mutex_unlock(&dev->mutex);
@@ -319,7 +329,7 @@ static ssize_t store_max_read_buffer_kb(struct device *csdev,
 
 	dev = info->device;
 	mutex_lock(&dev->mutex);
-	s = comedi_read_subdevice(info);
+	s = comedi_read_subdevice(dev, minor);
 	if (s && (s->subdev_flags & SDF_CMD_READ) && s->async)
 		s->async->max_bufsize = size;
 	else
@@ -344,7 +354,7 @@ static ssize_t show_read_buffer_kb(struct device *csdev,
 
 	dev = info->device;
 	mutex_lock(&dev->mutex);
-	s = comedi_read_subdevice(info);
+	s = comedi_read_subdevice(dev, minor);
 	if (s && (s->subdev_flags & SDF_CMD_READ) && s->async)
 		size = s->async->prealloc_bufsz / 1024;
 	mutex_unlock(&dev->mutex);
@@ -376,7 +386,7 @@ static ssize_t store_read_buffer_kb(struct device *csdev,
 
 	dev = info->device;
 	mutex_lock(&dev->mutex);
-	s = comedi_read_subdevice(info);
+	s = comedi_read_subdevice(dev, minor);
 	if (s && (s->subdev_flags & SDF_CMD_READ) && s->async)
 		err = resize_async_buffer(dev, s, s->async, size);
 	else
@@ -402,7 +412,7 @@ static ssize_t show_max_write_buffer_kb(struct device *csdev,
 
 	dev = info->device;
 	mutex_lock(&dev->mutex);
-	s = comedi_write_subdevice(info);
+	s = comedi_write_subdevice(dev, minor);
 	if (s && (s->subdev_flags & SDF_CMD_WRITE) && s->async)
 		size = s->async->max_bufsize / 1024;
 	mutex_unlock(&dev->mutex);
@@ -434,7 +444,7 @@ static ssize_t store_max_write_buffer_kb(struct device *csdev,
 
 	dev = info->device;
 	mutex_lock(&dev->mutex);
-	s = comedi_write_subdevice(info);
+	s = comedi_write_subdevice(dev, minor);
 	if (s && (s->subdev_flags & SDF_CMD_WRITE) && s->async)
 		s->async->max_bufsize = size;
 	else
@@ -459,7 +469,7 @@ static ssize_t show_write_buffer_kb(struct device *csdev,
 
 	dev = info->device;
 	mutex_lock(&dev->mutex);
-	s = comedi_write_subdevice(info);
+	s = comedi_write_subdevice(dev, minor);
 	if (s && (s->subdev_flags & SDF_CMD_WRITE) && s->async)
 		size = s->async->prealloc_bufsz / 1024;
 	mutex_unlock(&dev->mutex);
@@ -491,7 +501,7 @@ static ssize_t store_write_buffer_kb(struct device *csdev,
 
 	dev = info->device;
 	mutex_lock(&dev->mutex);
-	s = comedi_write_subdevice(info);
+	s = comedi_write_subdevice(dev, minor);
 	if (s && (s->subdev_flags & SDF_CMD_WRITE) && s->async)
 		err = resize_async_buffer(dev, s, s->async, size);
 	else
@@ -741,7 +751,6 @@ static int do_devinfo_ioctl(struct comedi_device *dev,
 			    struct file *file)
 {
 	const unsigned minor = iminor(file_inode(file));
-	struct comedi_file_info *info = comedi_file_info_from_minor(minor);
 	struct comedi_subdevice *s;
 	struct comedi_devinfo devinfo;
 
@@ -753,13 +762,13 @@ static int do_devinfo_ioctl(struct comedi_device *dev,
 	strlcpy(devinfo.driver_name, dev->driver->driver_name, COMEDI_NAMELEN);
 	strlcpy(devinfo.board_name, dev->board_name, COMEDI_NAMELEN);
 
-	s = comedi_read_subdevice(info);
+	s = comedi_read_subdevice(dev, minor);
 	if (s)
 		devinfo.read_subdevice = s->index;
 	else
 		devinfo.read_subdevice = -1;
 
-	s = comedi_write_subdevice(info);
+	s = comedi_write_subdevice(dev, minor);
 	if (s)
 		devinfo.write_subdevice = s->index;
 	else
@@ -1936,9 +1945,9 @@ static int comedi_mmap(struct file *file, struct vm_area_struct *vma)
 	}
 
 	if (vma->vm_flags & VM_WRITE)
-		s = comedi_write_subdevice(info);
+		s = comedi_write_subdevice(dev, minor);
 	else
-		s = comedi_read_subdevice(info);
+		s = comedi_read_subdevice(dev, minor);
 	if (!s) {
 		retval = -EINVAL;
 		goto done;
@@ -2008,7 +2017,7 @@ static unsigned int comedi_poll(struct file *file, poll_table *wait)
 		goto done;
 	}
 
-	s = comedi_read_subdevice(info);
+	s = comedi_read_subdevice(dev, minor);
 	if (s && s->async) {
 		poll_wait(file, &s->async->wait_head, wait);
 		if (!s->busy || !comedi_is_subdevice_running(s) ||
@@ -2016,7 +2025,7 @@ static unsigned int comedi_poll(struct file *file, poll_table *wait)
 			mask |= POLLIN | POLLRDNORM;
 	}
 
-	s = comedi_write_subdevice(info);
+	s = comedi_write_subdevice(dev, minor);
 	if (s && s->async) {
 		unsigned int bps = bytes_per_sample(s->async->subdevice);
 
@@ -2051,7 +2060,7 @@ static ssize_t comedi_write(struct file *file, const char __user *buf,
 		return -ENODEV;
 	}
 
-	s = comedi_write_subdevice(info);
+	s = comedi_write_subdevice(dev, minor);
 	if (!s || !s->async)
 		return -EIO;
 
@@ -2146,7 +2155,7 @@ static ssize_t comedi_read(struct file *file, char __user *buf, size_t nbytes,
 		return -ENODEV;
 	}
 
-	s = comedi_read_subdevice(info);
+	s = comedi_read_subdevice(dev, minor);
 	if (!s || !s->async)
 		return -EIO;