staging: comedi: don't hijack hardware device private data

comedi_auto_config() associates a Comedi minor device number with an
auto-configured hardware device and comedi_auto_unconfig() disassociates
it.  Currently, these use the hardware device's private data pointer to
point to some allocated storage holding the minor device number.  This
is a bit of a waste of the hardware device's private data pointer,
preventing it from being used for something more useful by the low-level
comedi device drivers.  For example, it would make more sense if
comedi_usb_auto_config() was passed a pointer to the struct
usb_interface instead of the struct usb_device, but this cannot be done
currently because the low-level comedi drivers already use the private
data pointer in the struct usb_interface for something more useful.

This patch stops the comedi core hijacking the hardware device's private
data pointer.  Instead, comedi_auto_config() stores a pointer to the
hardware device's struct device in the struct comedi_device_file_info
associated with the minor device number, and comedi_auto_unconfig()
calls new function comedi_find_board_minor() to recover the minor device
number associated with the hardware device.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 18 insertions, 0 deletions

diff --git a/drivers/staging/comedi/comedi_fops.c b/drivers/staging/comedi/comedi_fops.c
index f5417a3df240..fdf42822b962 100644
--- a/drivers/staging/comedi/comedi_fops.c
+++ b/drivers/staging/comedi/comedi_fops.c
@@ -2205,6 +2205,7 @@ int comedi_alloc_board_minor(struct device *hardware_device)
 		kfree(info);
 		return -ENOMEM;
 	}
+	info->hardware_device = hardware_device;
 	comedi_device_init(info->device);
 	spin_lock(&comedi_file_info_table_lock);
 	for (i = 0; i < COMEDI_NUM_BOARD_MINORS; ++i) {
@@ -2292,6 +2293,23 @@ void comedi_free_board_minor(unsigned minor)
 	}
 }
 
+int comedi_find_board_minor(struct device *hardware_device)
+{
+	int minor;
+	struct comedi_device_file_info *info;
+
+	for (minor = 0; minor < COMEDI_NUM_BOARD_MINORS; minor++) {
+		spin_lock(&comedi_file_info_table_lock);
+		info = comedi_file_info_table[minor];
+		if (info && info->hardware_device == hardware_device) {
+			spin_unlock(&comedi_file_info_table_lock);
+			return minor;
+		}
+		spin_unlock(&comedi_file_info_table_lock);
+	}
+	return -ENODEV;
+}
+
 int comedi_alloc_subdevice_minor(struct comedi_device *dev,
 				 struct comedi_subdevice *s)
 {