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staging: comedi: simplify driver module counting

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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>
This commit is contained in:
Ian Abbott 2013-04-04 14:58:56 +01:00 • committed by Greg Kroah-Hartman
parent d9740a0314
commit b2a644b435
2 changed files with 17 additions and 27 deletions
drivers/staging/comedi
comedi_fops.cdrivers.c

12
drivers/staging/comedi/comedi_fops.c
View file

@ -520,7 +520,6 @@ static int do_devconfig_ioctl(struct comedi_device *dev,
struct comedi_devconfig __user *arg)
{
struct comedi_devconfig it;
int ret;
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
@ -551,15 +550,8 @@ static int do_devconfig_ioctl(struct comedi_device *dev,
/* don't re-use dynamically allocated comedi devices */
return -EBUSY;
ret = comedi_device_attach(dev, &it);
if (ret == 0) {
if (!try_module_get(dev->driver->module)) {
comedi_device_detach(dev);
ret = -ENOSYS;
}
}
return ret;
/* This increments the driver module count on success. */
return comedi_device_attach(dev, &it);
}
/*

32
drivers/staging/comedi/drivers.c
View file

@ -277,11 +277,11 @@ static int __comedi_device_postconfig(struct comedi_device *dev)
}
/* 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 @@ int comedi_device_attach(struct comedi_device *dev, struct comedi_devconfig *it)
__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 @@ int comedi_auto_config(struct device *hardware_device,
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)