Introduce a comedi core helper function to handle the boilerplate
needed by the drivers to busy- wait for a condition to occur.
Typically this condition is the analog input/output end-of-conversion
used with the comedi (*insn_read) and (*insn_write) operations.

To use this function, the drivers just need to provide a callback
that checks for the desired condition. The callback should return
0 if the condition is met or -EBUSY if it is still waiting. Any
other errno will be returned to the caller. If the timeout occurs
before the condition is met -ETIMEDOUT will be returned.

The parameters to the callback function are the comedi_device,
comedi_subdevice, and comedi_insn pointers that were passed to the
(*insn_read) or (*insn_write) as well as an unsigned long, driver
specific, 'context' that can be used to pass any other information
that might be needed in the callback. This 'context' could be anything
such as the register offset to read the status or the bits needed
to check the status. The comedi_timeout() function itself does not
use any of these parameters.

This will help remove all the crazy "wait this many loops" used by
some of the drivers. It also creates a common errno for comedi to
detect when a timeout occurs.

ADC/DAC conversion times are typically pretty fast, usually around
100K samples/sec (10 usec). A conservative timeout of 1 second is used
in comedi_timeout().

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

`comedi_auto_config()` is usually called from the probe routine of a
low-level comedi driver to allocate and auto-configure a comedi device.
Part of this involves calling the low-level driver's `auto_attach()`
handler, and if that is successful, `comedi_device_postconfig()` tries
to complete the configuration of the comedi device.  If either of those
fail, `comedi_device_detach()` is called to clean up, and
`comedi_release_hardware_device()` is called to remove the dynamically
allocated comedi device.

Unfortunately, `comedi_device_detach()` clears the `hw_dev` member of
the `struct comedi_device` (indirectly via `comedi_clear_hw_dev()`), and
that stops `comedi_release_hardware_device()` finding the comedi device
associated with the hardware device, so the comedi device won't be
removed properly.

Since `comedi_release_hardware_device()` also calls
`comedi_device_detach()` (assuming it finds the comedi device associated
with the hardware device), the fix is to remove the direct call to
`comedi_device_detach()` from `comedi_auto_config()` and let the call to
`comedi_release_hardware_device()` take care of it.

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

Added success message to the driver autoconfig and error
message in case it fails. A success message is required
so that the user can find out which comedi driver has been
associated with which udev device. This also makes troubleshooting
much easier when more than one card is in the computer or
there is a mix of USB and PCI devices.
As Ian suggested we should report both the driver and the board
which might have different names, especially if one driver covers a
range of different boards.

Signed-off-by: Bernd Porr <mail@berndporr.me.uk>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

This resolves a merge issue with drivers/staging/imx-drm/imx-drm-core.c

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Some of the callback functions that upload the firmware in the comedi
drivers return a positive value indicating the number of bytes sent
to the device. Detect this condition and just return '0' to indicate
a successful upload.

Reported-by: Bernd Porr <mail@berndporr.me.uk>
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Acked-by: Ian Abbott <abbotti@mev.co.uk>
Acked-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Change `comedi_driver_unregister()` to call
`comedi_dev_get_from_minor()` instead of `comedi_dev_from_minor()` when
finding devices using the driver.  This increments the reference count
to prevent the device being removed while it is being checked to see if
it is attached to the driver.  Call `comedi_dev_put()` to decrement the
reference afterwards.

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

Add a member `detach_count` to `struct comedi_device` that is
incremented every time the device gets detached.  This will be used in
some validity checks in the 'read' and 'write' file operations to make
sure the attachment remains valid.

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

The comedi core module's handling of the `COMEDI_DEVCONFIG` ioctl will
not allow a device to be detached if it is busy.  However, comedi
devices can also be auto-detached due to a removal of a hardware device.
One of the things we should do in that case is cancel any asynchronous
commands that are running.  Add a new function
`comedi_device_cancel_all()` to do that and call it from
`comedi_device_detach()`.

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

Rename the local function `cleanup_device()` to
`comedi_device_detach_cleanup()`.  It is only called from the
`comedi_device_detach()` function and that is called from
`comedi_device_cleanup()` and other places.  The more specific function
name seems less confusing.

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

Acquire the `attach_lock` semaphore in the `struct comedi_device` while
modifying the `attached` flag.  This is a "write" acquire.  Note that
the main mutex in the `struct comedi_device` is also held at this time.
Tasks wishing to check the device is attached will need to either
acquire the main mutex, or "read" acquire the `attach_lock` semaphore,
or both in that order.

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