If the "write" file operation handler, `comedi_write()` is passed 0 for
the amount to write, some error conditions are currently skipped and the
function just returns 0.  Change it to check those error conditions and
return an error value if appropriate.  The trickiest case is the check
for when the previously set up asynchronous command has terminated with
an error.  In that case, `-EPIPE` is returned (as it is for a write of
non-zero length) and the subdevice gets marked as non-busy.

A zero-length write that returns 0 has no other effects, in particular,
it does not cause the subdevice to be marked as non-busy.
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>

In order to perform a "write" file operation, an asynchronous COMEDI
command in the "write" direction needs to have been set up by the
current file object on the COMEDI "write" subdevice associated with the
file object.  If there is a "write" subdevice, but a command has not
been set up by the file object (or is has been set-up in the wrong
direction), `comedi_write()` currently returns one of two error values
`-EINVAL` or `-EACCES`.  `-EACCES` is returned if the command was set up
by a different subdevice, or somewhat randomly, if a COMEDI
"instruction" is currently being processed.  `-EINVAL` is returned in
other cases.  Simplify it by returning `-EINVAL` for all these cases.
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>

The "write" file operation handler, `comedi_write()` returns an error
for pretty much any condition that prevents a "write" going ahead.  One
of the conditions that prevents a "write" going ahead is that no
asynchronous command has been set up, but that currently results in a
return value of 0 (unless COMEDI instructions are being processed or an
asynchronous command has been set up by a different file object).
Change it to return `-EINVAL` in this case.
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>

`comedi_write()` copies data from the user buffer to the acquisition
data buffer, which is cyclic, using a single call to `copy_from_user()`.
It currently avoids having to deal with wraparound of the cyclic buffer
by limiting the amount it copies (and the amount returned to the user).
Change it to deal with the wraparound using two calls to
`copy_from_user()` if necessary.
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>

At one point in `comedi_write()`, the variable `n` gets assigned to the
minimum of the parameter `nbytes` and the amount of writeable buffer
space.  The way that is done currently is unsafe in the unlikely case
that `nbytes` exceeds `UINT_MAX`, so fix it.
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>

In `comedi_write()`, the `n` and `m` variables are of type `int`.
Change them to `unsigned int` as they are used to measure a positive
number of bytes.  The `count` variable is also of type `int` and holds
the returned number of bytes written.  Change it to type `ssize_t` to
match the function's return type.
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>

`comedi_write()` is the handler for the "write" file operation for
COMEDI devices.  It mostly runs without using the main mutex of the
COMEDI device, but uses the `attach_lock` rw_semaphore to protect
against the COMEDI device becoming "detached".  A file object can write
data for a COMEDI asynchonous command if it initiated the command.  The
COMEDI subdevice is marked as busy when the command is started.  At some
point, the "write" handler detects that the command has terminated and
so marks the subdevice as non-busy.

In order to mark the subdevice as non-busy, the "write" handler needs to
release the `attach_lock` rw_semaphore and `acquire the main `mutex`.
There is a vulnerable point between the two, so it checks that the
device is still attached after acquiring the mutex.  However, it does
not currently check that the conditions for becoming non-busy still
hold.  Add some more checks that the subdevice is still busy with a
command initiated by the same file object, and that the command is in
the correct direction (in case the subdevice supports both "read" and
"write").
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>

Rearrange the code in `comedi_write()` to reduce the amount of
indentation.  The code never reiterates the `while` loop once `count`
has become non-zero, so we can check that in the `while` condition to
save an indentation level.  (Note that `nbytes` has been checked to be
non-zero before entering the loop, so we can remove that check.)  Move
the code that makes the subdevice "become non-busy" outside the `while`
loop, using a new flag variable `become_nonbusy` to decide whether it
needs to be done.  This simplifies the wait queue handling so there is a
single place where the task is removed from the wait queue, and we can
remove the `on_wait_queue` flag variable.
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>

Change the MODULE_DESCRIPTION to something more useful than the
generic "Comedi low-level driver".
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

The Description is a bit long winded and the same information is in
the Devices. Shorten the Description and tidy up the Devices.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

This function is called as part of the pci_driver (*probe) before
doing the (*auto_attach) of the comedi driver. For aesthetics, move
the function to a more logical place in the driver.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

For aesthetics, move these defines after the register defines and rename
them to have namespace associated with the driver.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

For aesthetics, move this enum after the register defines and rename
it to have namespace associated with the driver.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

This member of the boardinfo is identical to the offset of the boardinfo
in the boardtypes array. It's also passed as the 'context' to the driver
(*auto_attach).

The 'cardtype' is only needed by the (*auto_attach) to determine which
PCI BAR to use and in pci_dio_reset() to handle the board specific code.

Remove the 'cardtype' member and use the 'context' value instead.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

For aesthetics, use a common define for the interrupt control and status
registers.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

For aesthetics, rename this define and fix the alignment.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

For aesthetics, replace these defines with a macro.

Refactor the switch in pci_dio_reset() to use common code.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

For aesthetics, replace these defines with some macros.

Refactor the switch in pci_dio_reset() to not require the fallthrough
comment.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

These boards use the same offsets for the interrupt control registers.
For aesthetics, remove the current defines and use common ones.

Fix the switch() in pci_dio_reset() to use common code.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

These boards use the same offsets for the interrupt control registers.
For aesthetics, remove the current defines and use common ones.

Fix the switch() in pci_dio_reset() to use common code.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

For aesthetics, use a common comment for the switch() that disables and clears
interrupts.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

For aesthetics, move the disable of the channel freeze for the PCI-1752
and PCI-1756 boards out of the switch used to disable and clear interrupts.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

For aesthetics, use a default case in the switch (board->cardtype) used
to reset the various boards.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

These defines are only used to initialize the diosubd_data 'addr' members
in the boardinfo. For aesthetics, just open-code the values and remove the
defines.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

These defines are only used to initialize the diosubd_data 'addr' members
in the boardinfo. For aesthetics, just open-code the values and remove the
defines.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Currently the board reset function also resets the digital output channels
to 0. This works but it makes the reset function a bit messy and each
board type has to be handled special.

Move the digital output reset into the subdevice init where it can be
handle based on the subdevice setup.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

The board reset function disables and clears all interrupts. It also
resets all the digital output channels to 0.

Interrupts are not currently used by this driver. For asthetics, do
the board reset early in the (*auto_attach) to make sure the interrupts
are disabled in case this feature is added.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

The board reset function disables and clears all interrupts. It also
resets all the digital output channels to 0.

Interrupts are not used by this driver so the disable/clear during the
(*detach) is not necessary.

Reseting all the digital outputs to 0 might not be desired depending
on what the outputs are connected to.

Remove the board reset and just use comedi_pci_detach() directly for
the driver (*detach).
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

These defines are only used to initialize the diosubd_data 'addr' members
in the boardinfo. For aesthetics, just open-code the values and remove the
defines.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

These defines are only used to initialize the 'timer_regbase' boardinfo.
For aesthetics, just open-code the values and remove the defines.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

The "board id" register is always 4-bits (4 di channels) and the register
used to read the bits is always > 0.

Simplify the 'boardid' boardinfo by replacing it with a 'id_reg' member
and open-coding the subdevice n_chan.

For aesthetics, remove all the *_BOARDID defines and just open-code the
register values in the boardinfo.

Add the missing boardinfo for the pci1739 board id register and increase
the nsubdevs to handle it.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Currently the di/do subdevices store a pointer to the diosubd_data in s->private.
The (*insn_bits) functions then use that to get to the 'addr' needed to access
the registers.

The only member of diosubd_data that is needed by the (*insn_bits) functions is
the 'addr'. For aesthetics, just store the 'addr' in s->private.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Currently the (*insn_bits) functions used the 'regs' member to determine how
many registers need to be read or written to update the subdevice. We can use
the subdevice 'n_chan' to determine this and make the code a bit clearer.

The (*auto_attach) also uses this member to determine how many 8255 devices
need to be initialized. These subdevices do not use the 'chans' member of
diosubd_data. Move the 'regs' value to the 'chans' to allow removing the
'regs' member completely.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

The boards supported by this driver either use 8-bit or 16-bit I/O. The
'io_access' member of the boardinfo is used by the (*auto_attach) to
determine which (*insn_bits) function to use.

Simplify the boardinfo a bit by refactoring the 'io_access' member into
a bit-field flag 'is_16bit'. Use the new flag and remove the switch ()
code in the (*auto_attach).
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

This function initializes a digitial input subdevices. For aesthetics,
absorb it into the (*auto_attach).

Remove the improper initialization of the SDF_LSAMPL subdev_flag and
len_chanlist. These are only used by subdevices that support async
commands.

Also, remove the unnecessary 'specflags' from the diosubd_data. Only
the boardid subdevice uses it.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

This function initializes a digitial output subdevice. For aesthetics,
absorb it into the (*auto_attach).

Remove the improper initialization of the SDF_LSAMPL subdev_flag and
len_chanlist. These are only used by subdevices that support async
commands.

Also remove the unnecessary initilaization of the subdevice 'state'.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

For aesthetics, use a const pointer to access the diosubd_data in the
boardinfo when doing the (*auto_attach)..
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

For aesthetics, post-increment the 'subdev' index when used to get a
comedi_subdevice pointer instead of incrementing it after the subdevice
is initialized.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

All the boards use PCI BAR2 for the dev->iobase except for the pci1736
which uses PCI BAR0. Just use the board->cardtype to determine which
PCI BAR to use.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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