staging: comedi: simplify driver module counting
For a legacy device attachment with the `COMEDI_DEVCONFIG` ioctl,
`do_devconfig_ioctl()` calls `comedi_device_attach()` to find a matching
device driver and attach the device. It then tries to increment the
device driver's module count and if that fails it detaches the device.
So on successful attachment of a device by the `COMEDI_DEVCONFIG` ioctl,
the device driver's module count will have been incremented.
`comedi_device_attach()` is called from nowhere else. It already
increments the device driver's module count temporarily and decrements
it again; if it gets as far as calling `comedi_device_postconfig()` the
module count is decremented within that function.
Simplify the above by removing the decrement of the device driver module
count from `comedi_device_postconfig()`. If the call to
`comedi_device_postconfig()` succeeds, `comedi_device_attach()` will
return with the module count still incremented, otherwise decrement the
module count before returning the error. Don't try and increment the
module count in `do_devconfig_ioctl()` after a successful return from
`comedi_device_attach()` as the module count has now already been
incremented.
`comedi_device_postconfig()` is also called by `comedi_auto_config()`
which currently has to increment the device driver's module count
temporarily so that `comedi_device_postconfig()` can decrement it, but
always returns with no overall change to the module count. Remove all
the module count manipulations from `comedi_device_postconfig()`. There
is no other reason for `comedi_auto_config()` to increment the device
driver's module count temporarily, since it is only called (indirectly)
from the device driver itself (usually via one of the wrappers
`comedi_pci_auto_config()` or `comedi_usb_auto_config()`).
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>
diff --git a/drivers/staging/comedi/drivers.c b/drivers/staging/comedi/drivers.c
index caadd3b..73727a7 100644
--- a/drivers/staging/comedi/drivers.c
+++ b/drivers/staging/comedi/drivers.c
@@ -277,11 +277,11 @@
}
/* do a little post-config cleanup */
-/* called with module refcount incremented, decrements it */
static int comedi_device_postconfig(struct comedi_device *dev)
{
- int ret = __comedi_device_postconfig(dev);
- module_put(dev->driver->module);
+ int ret;
+
+ ret = __comedi_device_postconfig(dev);
if (ret < 0) {
__comedi_device_detach(dev);
return ret;
@@ -400,7 +400,11 @@
__comedi_device_detach(dev);
return ret;
}
- return comedi_device_postconfig(dev);
+ ret = comedi_device_postconfig(dev);
+ if (ret < 0)
+ module_put(dev->driver->module);
+ /* On success, the driver module count has been incremented. */
+ return ret;
}
int comedi_auto_config(struct device *hardware_device,
@@ -431,19 +435,13 @@
return PTR_ERR(comedi_dev);
/* Note: comedi_alloc_board_minor() locked comedi_dev->mutex. */
- if (!try_module_get(driver->module))
- ret = -EIO;
- else {
- comedi_set_hw_dev(comedi_dev, hardware_device);
- comedi_dev->driver = driver;
- ret = driver->auto_attach(comedi_dev, context);
- if (ret < 0) {
- module_put(driver->module);
- __comedi_device_detach(comedi_dev);
- } else {
- ret = comedi_device_postconfig(comedi_dev);
- }
- }
+ comedi_set_hw_dev(comedi_dev, hardware_device);
+ comedi_dev->driver = driver;
+ ret = driver->auto_attach(comedi_dev, context);
+ if (ret < 0)
+ __comedi_device_detach(comedi_dev);
+ else
+ ret = comedi_device_postconfig(comedi_dev);
mutex_unlock(&comedi_dev->mutex);
if (ret < 0)
