staging: comedi: drivers.c: document exported functions

Add missing kernel-doc to the low-level COMEDI driver API functions
exported from "drivers.c" and tart up some of the existing kernel-doc
comments for consistency.

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

1 files changed, 258 insertions, 69 deletions

diff --git a/drivers/staging/comedi/drivers.c b/drivers/staging/comedi/drivers.c
index 7118117..aae9481 100644
--- a/drivers/staging/comedi/drivers.c
+++ b/drivers/staging/comedi/drivers.c
@@ -34,6 +34,28 @@ struct comedi_driver *comedi_drivers;
 /* protects access to comedi_drivers */
 DEFINE_MUTEX(comedi_drivers_list_lock);
 
+/**
+ * comedi_set_hw_dev() - Set hardware device associated with COMEDI device
+ * @dev: COMEDI device.
+ * @hw_dev: Hardware device.
+ *
+ * For automatically configured COMEDI devices (resulting from a call to
+ * comedi_auto_config() or one of its wrappers from the low-level COMEDI
+ * driver), comedi_set_hw_dev() is called automatically by the COMEDI core
+ * to associate the COMEDI device with the hardware device.  It can also be
+ * called directly by "legacy" low-level COMEDI drivers that rely on the
+ * %COMEDI_DEVCONFIG ioctl to configure the hardware as long as the hardware
+ * has a &struct device.
+ *
+ * If @dev->hw_dev is NULL, it gets a reference to @hw_dev and sets
+ * @dev->hw_dev, otherwise, it does nothing.  Calling it multiple times
+ * with the same hardware device is not considered an error.  If it gets
+ * a reference to the hardware device, it will be automatically 'put' when
+ * the device is detached from COMEDI.
+ *
+ * Returns 0 if @dev->hw_dev was NULL or the same as @hw_dev, otherwise
+ * returns -EEXIST.
+ */
 int comedi_set_hw_dev(struct comedi_device *dev, struct device *hw_dev)
 {
 	if (hw_dev == dev->hw_dev)
@@ -52,9 +74,15 @@ static void comedi_clear_hw_dev(struct comedi_device *dev)
 }
 
 /**
- * comedi_alloc_devpriv() - Allocate memory for the device private data.
- * @dev: comedi_device struct
- * @size: size of the memory to allocate
+ * comedi_alloc_devpriv() - Allocate memory for the device private data
+ * @dev: COMEDI device.
+ * @size: Size of the memory to allocate.
+ *
+ * The allocated memory is zero-filled.  @dev->private points to it on
+ * return.  The memory will be automatically freed when the COMEDI device is
+ * "detached".
+ *
+ * Returns a pointer to the allocated memory, or NULL on failure.
  */
 void *comedi_alloc_devpriv(struct comedi_device *dev, size_t size)
 {
@@ -63,6 +91,18 @@ void *comedi_alloc_devpriv(struct comedi_device *dev, size_t size)
 }
 EXPORT_SYMBOL_GPL(comedi_alloc_devpriv);
 
+/**
+ * comedi_alloc_subdevices() - Allocate subdevices for COMEDI device
+ * @dev: COMEDI device.
+ * @num_subdevices: Number of subdevices to allocate.
+ *
+ * Allocates and initializes an array of &struct comedi_subdevice for the
+ * COMEDI device.  If successful, sets @dev->subdevices to point to the
+ * first one and @dev->n_subdevices to the number.
+ *
+ * Returns 0 on success, -EINVAL if @num_subdevices is < 1, or -ENOMEM if
+ * failed to allocate the memory.
+ */
 int comedi_alloc_subdevices(struct comedi_device *dev, int num_subdevices)
 {
 	struct comedi_subdevice *s;
@@ -90,8 +130,22 @@ int comedi_alloc_subdevices(struct comedi_device *dev, int num_subdevices)
 EXPORT_SYMBOL_GPL(comedi_alloc_subdevices);
 
 /**
- * comedi_alloc_subdev_readback() - Allocate memory for the subdevice readback.
- * @s: comedi_subdevice struct
+ * comedi_alloc_subdev_readback() - Allocate memory for the subdevice readback
+ * @s: COMEDI subdevice.
+ *
+ * This is called by low-level COMEDI drivers to allocate an array to record
+ * the last values written to a subdevice's analog output channels (at least
+ * by the %INSN_WRITE instruction), to allow them to be read back by an
+ * %INSN_READ instruction.  It also provides a default handler for the
+ * %INSN_READ instruction unless one has already been set.
+ *
+ * On success, @s->readback points to the first element of the array, which
+ * is zero-filled.  The low-level driver is responsible for updating its
+ * contents.  @s->insn_read will be set to comedi_readback_insn_read()
+ * unless it is already non-NULL.
+ *
+ * Returns 0 on success, -EINVAL if the subdevice has no channels, or
+ * -ENOMEM on allocation failure.
  */
 int comedi_alloc_subdev_readback(struct comedi_subdevice *s)
 {
@@ -174,10 +228,20 @@ int insn_inval(struct comedi_device *dev, struct comedi_subdevice *s,
 
 /**
  * comedi_readback_insn_read() - A generic (*insn_read) for subdevice readback.
- * @dev: comedi_device struct
- * @s: comedi_subdevice struct
- * @insn: comedi_insn struct
- * @data: pointer to return the readback data
+ * @dev: COMEDI device.
+ * @s: COMEDI subdevice.
+ * @insn: COMEDI instruction.
+ * @data: Pointer to return the readback data.
+ *
+ * Handles the %INSN_READ instruction for subdevices that use the readback
+ * array allocated by comedi_alloc_subdev_readback().  It may be used
+ * directly as the subdevice's handler (@s->insn_read) or called via a
+ * wrapper.
+ *
+ * @insn->n is normally 1, which will read a single value.  If higher, the
+ * same element of the readback array will be read multiple times.
+ *
+ * Returns @insn->n on success, or -EINVAL if @s->readback is NULL.
  */
 int comedi_readback_insn_read(struct comedi_device *dev,
 			      struct comedi_subdevice *s,
@@ -198,12 +262,21 @@ int comedi_readback_insn_read(struct comedi_device *dev,
 EXPORT_SYMBOL_GPL(comedi_readback_insn_read);
 
 /**
- * comedi_timeout() - busy-wait for a driver condition to occur.
- * @dev: comedi_device struct
- * @s: comedi_subdevice struct
- * @insn: comedi_insn struct
- * @cb: callback to check for the condition
- * @context: private context from the driver
+ * comedi_timeout() - Busy-wait for a driver condition to occur
+ * @dev: COMEDI device.
+ * @s: COMEDI subdevice.
+ * @insn: COMEDI instruction.
+ * @cb: Callback to check for the condition.
+ * @context: Private context from the driver.
+ *
+ * Busy-waits for up to a second (%COMEDI_TIMEOUT_MS) for the condition or
+ * some error (other than -EBUSY) to occur.  The parameters @dev, @s, @insn,
+ * and @context are passed to the callback function, which returns -EBUSY to
+ * continue waiting or some other value to stop waiting (generally 0 if the
+ * condition occurred, or some error value).
+ *
+ * Returns -ETIMEDOUT if timed out, otherwise the return value from the
+ * callback function.
  */
 int comedi_timeout(struct comedi_device *dev,
 		   struct comedi_subdevice *s,
@@ -228,12 +301,30 @@ int comedi_timeout(struct comedi_device *dev,
 EXPORT_SYMBOL_GPL(comedi_timeout);
 
 /**
- * comedi_dio_insn_config() - boilerplate (*insn_config) for DIO subdevices.
- * @dev: comedi_device struct
- * @s: comedi_subdevice struct
- * @insn: comedi_insn struct
- * @data: parameters for the @insn
- * @mask: io_bits mask for grouped channels
+ * comedi_dio_insn_config() - Boilerplate (*insn_config) for DIO subdevices
+ * @dev: COMEDI device.
+ * @s: COMEDI subdevice.
+ * @insn: COMEDI instruction.
+ * @data: Instruction parameters and return data.
+ * @mask: io_bits mask for grouped channels, or 0 for single channel.
+ *
+ * If @mask is 0, it is replaced with a single-bit mask corresponding to the
+ * channel number specified by @insn->chanspec.  Otherwise, @mask
+ * corresponds to a group of channels (which should include the specified
+ * channel) that are always configured together as inputs or outputs.
+ *
+ * Partially handles the %INSN_CONFIG_DIO_INPUT, %INSN_CONFIG_DIO_OUTPUTS,
+ * and %INSN_CONFIG_DIO_QUERY instructions.  The first two update
+ * @s->io_bits to record the directions of the masked channels.  The last
+ * one sets @data[1] to the current direction of the group of channels
+ * (%COMEDI_INPUT) or %COMEDI_OUTPUT) as recorded in @s->io_bits.
+ *
+ * The caller is responsible for updating the DIO direction in the hardware
+ * registers if this function returns 0.
+ *
+ * Returns 0 for a %INSN_CONFIG_DIO_INPUT or %INSN_CONFIG_DIO_OUTPUT
+ * instruction, @insn->n (> 0) for a %INSN_CONFIG_DIO_QUERY instruction, or
+ * -EINVAL for some other instruction.
  */
 int comedi_dio_insn_config(struct comedi_device *dev,
 			   struct comedi_subdevice *s,
@@ -268,9 +359,18 @@ int comedi_dio_insn_config(struct comedi_device *dev,
 EXPORT_SYMBOL_GPL(comedi_dio_insn_config);
 
 /**
- * comedi_dio_update_state() - update the internal state of DIO subdevices.
- * @s: comedi_subdevice struct
- * @data: the channel mask and bits to update
+ * comedi_dio_update_state() - Update the internal state of DIO subdevices
+ * @s: COMEDI subdevice.
+ * @data: The channel mask and bits to update.
+ *
+ * Updates @s->state which holds the internal state of the outputs for DIO
+ * or DO subdevices (up to 32 channels).  @data[0] contains a bit-mask of
+ * the channels to be updated.  @data[1] contains a bit-mask of those
+ * channels to be set to '1'.  The caller is responsible for updating the
+ * outputs in hardware according to @s->state.  As a minimum, the channels
+ * in the returned bit-mask need to be updated.
+ *
+ * Returns @mask with non-existent channels removed.
  */
 unsigned int comedi_dio_update_state(struct comedi_subdevice *s,
 				     unsigned int *data)
@@ -290,17 +390,17 @@ unsigned int comedi_dio_update_state(struct comedi_subdevice *s,
 EXPORT_SYMBOL_GPL(comedi_dio_update_state);
 
 /**
- * comedi_bytes_per_scan - get length of asynchronous command "scan" in bytes
- * @s: comedi_subdevice struct
+ * comedi_bytes_per_scan() - Get length of asynchronous command "scan" in bytes
+ * @s: COMEDI subdevice.
  *
  * Determines the overall scan length according to the subdevice type and the
  * number of channels in the scan.
  *
- * For digital input, output or input/output subdevices, samples for multiple
- * channels are assumed to be packed into one or more unsigned short or
- * unsigned int values according to the subdevice's SDF_LSAMPL flag.  For other
- * types of subdevice, samples are assumed to occupy a whole unsigned short or
- * unsigned int according to the SDF_LSAMPL flag.
+ * For digital input, output or input/output subdevices, samples for
+ * multiple channels are assumed to be packed into one or more unsigned
+ * short or unsigned int values according to the subdevice's %SDF_LSAMPL
+ * flag.  For other types of subdevice, samples are assumed to occupy a
+ * whole unsigned short or unsigned int according to the %SDF_LSAMPL flag.
  *
  * Returns the overall scan length in bytes.
  */
@@ -326,18 +426,18 @@ unsigned int comedi_bytes_per_scan(struct comedi_subdevice *s)
 EXPORT_SYMBOL_GPL(comedi_bytes_per_scan);
 
 /**
- * comedi_nscans_left - return the number of scans left in the command
- * @s: comedi_subdevice struct
- * @nscans: the expected number of scans
+ * comedi_nscans_left() - Return the number of scans left in the command
+ * @s: COMEDI subdevice.
+ * @nscans: The expected number of scans or 0 for all available scans.
  *
- * If nscans is 0, the number of scans available in the async buffer will be
- * used. Otherwise the expected number of scans will be used.
+ * If @nscans is 0, it is set to the number of scans available in the
+ * async buffer.
  *
- * If the async command has a stop_src of TRIG_COUNT, the nscans will be
- * checked against the number of scans left in the command.
+ * If the async command has a stop_src of %TRIG_COUNT, the @nscans will be
+ * checked against the number of scans remaining to complete the command.
  *
  * The return value will then be either the expected number of scans or the
- * number of scans remaining in the command.
+ * number of scans remaining to complete the command, whichever is fewer.
  */
 unsigned int comedi_nscans_left(struct comedi_subdevice *s,
 				unsigned int nscans)
@@ -365,12 +465,12 @@ unsigned int comedi_nscans_left(struct comedi_subdevice *s,
 EXPORT_SYMBOL_GPL(comedi_nscans_left);
 
 /**
- * comedi_nsamples_left - return the number of samples left in the command
- * @s: comedi_subdevice struct
- * @nsamples: the expected number of samples
+ * comedi_nsamples_left() - Return the number of samples left in the command
+ * @s: COMEDI subdevice.
+ * @nsamples: The expected number of samples.
  *
- * Returns the expected number of samples of the number of samples remaining
- * in the command.
+ * Returns the number of samples remaining to complete the command, or the
+ * specified expected number of samples (@nsamples), whichever is fewer.
  */
 unsigned int comedi_nsamples_left(struct comedi_subdevice *s,
 				  unsigned int nsamples)
@@ -399,14 +499,14 @@ unsigned int comedi_nsamples_left(struct comedi_subdevice *s,
 EXPORT_SYMBOL_GPL(comedi_nsamples_left);
 
 /**
- * comedi_inc_scan_progress - update scan progress in asynchronous command
- * @s: comedi_subdevice struct
- * @num_bytes: amount of data in bytes to increment scan progress
+ * comedi_inc_scan_progress() - Update scan progress in asynchronous command
+ * @s: COMEDI subdevice.
+ * @num_bytes: Amount of data in bytes to increment scan progress.
  *
- * Increments the scan progress by the number of bytes specified by num_bytes.
+ * Increments the scan progress by the number of bytes specified by @num_bytes.
  * If the scan progress reaches or exceeds the scan length in bytes, reduce
  * it modulo the scan length in bytes and set the "end of scan" asynchronous
- * event flag to be processed later.
+ * event flag (%COMEDI_CB_EOS) to be processed later.
  */
 void comedi_inc_scan_progress(struct comedi_subdevice *s,
 			      unsigned int num_bytes)
@@ -437,12 +537,12 @@ void comedi_inc_scan_progress(struct comedi_subdevice *s,
 EXPORT_SYMBOL_GPL(comedi_inc_scan_progress);
 
 /**
- * comedi_handle_events - handle events and possibly stop acquisition
- * @dev: comedi_device struct
- * @s: comedi_subdevice struct
+ * comedi_handle_events() - Handle events and possibly stop acquisition
+ * @dev: COMEDI device.
+ * @s: COMEDI subdevice.
  *
  * Handles outstanding asynchronous acquisition event flags associated
- * with the subdevice.  Call the subdevice's "->cancel()" handler if the
+ * with the subdevice.  Call the subdevice's @s->cancel() handler if the
  * "end of acquisition", "error" or "overflow" event flags are set in order
  * to stop the acquisition at the driver level.
  *
@@ -677,12 +777,19 @@ static void comedi_report_boards(struct comedi_driver *driv)
 }
 
 /**
- * comedi_load_firmware() - Request and load firmware for a device.
- * @dev: comedi_device struct
- * @hw_device: device struct for the comedi_device
- * @name: the name of the firmware image
- * @cb: callback to the upload the firmware image
- * @context: private context from the driver
+ * comedi_load_firmware() - Request and load firmware for a device
+ * @dev: COMEDI device.
+ * @device: Hardware device.
+ * @name: The name of the firmware image.
+ * @cb: Callback to the upload the firmware image.
+ * @context: Private context from the driver.
+ *
+ * Sends a firmware request for the hardware device and waits for it.  Calls
+ * the callback function to upload the firmware to the device, them releases
+ * the firmware.
+ *
+ * Returns 0 on success, -EINVAL if @cb is NULL, or a negative error number
+ * from the firmware request or the callback function.
  */
 int comedi_load_firmware(struct comedi_device *dev,
 			 struct device *device,
@@ -709,10 +816,16 @@ int comedi_load_firmware(struct comedi_device *dev,
 EXPORT_SYMBOL_GPL(comedi_load_firmware);
 
 /**
- * __comedi_request_region() - Request an I/O reqion for a legacy driver.
- * @dev: comedi_device struct
- * @start: base address of the I/O reqion
- * @len: length of the I/O region
+ * __comedi_request_region() - Request an I/O region for a legacy driver
+ * @dev: COMEDI device.
+ * @start: Base address of the I/O region.
+ * @len: Length of the I/O region.
+ *
+ * Requests the specified I/O port region which must start at a non-zero
+ * address.
+ *
+ * Returns 0 on success, -EINVAL if @start is 0, or -EIO if the request
+ * fails.
  */
 int __comedi_request_region(struct comedi_device *dev,
 			    unsigned long start, unsigned long len)
@@ -735,10 +848,19 @@ int __comedi_request_region(struct comedi_device *dev,
 EXPORT_SYMBOL_GPL(__comedi_request_region);
 
 /**
- * comedi_request_region() - Request an I/O reqion for a legacy driver.
- * @dev: comedi_device struct
- * @start: base address of the I/O reqion
- * @len: length of the I/O region
+ * comedi_request_region() - Request an I/O region for a legacy driver
+ * @dev: COMEDI device.
+ * @start: Base address of the I/O region.
+ * @len: Length of the I/O region.
+ *
+ * Requests the specified I/O port region which must start at a non-zero
+ * address.
+ *
+ * On success, @dev->iobase is set to the base address of the region and
+ * @dev->iolen is set to its length.
+ *
+ * Returns 0 on success, -EINVAL if @start is 0, or -EIO if the request
+ * fails.
  */
 int comedi_request_region(struct comedi_device *dev,
 			  unsigned long start, unsigned long len)
@@ -756,8 +878,16 @@ int comedi_request_region(struct comedi_device *dev,
 EXPORT_SYMBOL_GPL(comedi_request_region);
 
 /**
- * comedi_legacy_detach() - A generic (*detach) function for legacy drivers.
- * @dev: comedi_device struct
+ * comedi_legacy_detach() - A generic (*detach) function for legacy drivers
+ * @dev: COMEDI device.
+ *
+ * This is a simple, generic 'detach' handler for legacy COMEDI devices that
+ * just use a single I/O port region and possibly an IRQ and that don't need
+ * any special clean-up for their private device or subdevice storage.  It
+ * can also be called by a driver-specific 'detach' handler.
+ *
+ * If @dev->irq is non-zero, the IRQ will be freed.  If @dev->iobase and
+ * @dev->iolen are both non-zero, the I/O port region will be released.
  */
 void comedi_legacy_detach(struct comedi_device *dev)
 {
@@ -831,6 +961,29 @@ out:
 	return ret;
 }
 
+/**
+ * comedi_auto_config() - Create a COMEDI device for a hardware device
+ * @hardware_device: Hardware device.
+ * @driver: COMEDI low-level driver for the hardware device.
+ * @context: Driver context for the auto_attach handler.
+ *
+ * Allocates a new COMEDI device for the hardware device and calls the
+ * low-level driver's 'auto_attach' handler to set-up the hardware and
+ * allocate the COMEDI subdevices.  Additional "post-configuration" setting
+ * up is performed on successful return from the 'auto_attach' handler.
+ * If the 'auto_attach' handler fails, the low-level driver's 'detach'
+ * handler will be called as part of the clean-up.
+ *
+ * This is usually called from a wrapper function in a bus-specific COMEDI
+ * module, which in turn is usually called from a bus device 'probe'
+ * function in the low-level driver.
+ *
+ * Returns 0 on success, -EINVAL if the parameters are invalid or the
+ * post-configuration determines the driver has set the COMEDI device up
+ * incorrectly, -ENOMEM if failed to allocate memory, -EBUSY if run out of
+ * COMEDI minor device numbers, or some negative error number returned by
+ * the driver's 'auto_attach' handler.
+ */
 int comedi_auto_config(struct device *hardware_device,
 		       struct comedi_driver *driver, unsigned long context)
 {
@@ -888,6 +1041,22 @@ int comedi_auto_config(struct device *hardware_device,
 }
 EXPORT_SYMBOL_GPL(comedi_auto_config);
 
+/**
+ * comedi_auto_unconfig() - Unconfigure auto-allocated COMEDI device
+ * @hardware_device: Hardware device previously passed to
+ *                   comedi_auto_config().
+ *
+ * Cleans up and eventually destroys the COMEDI device allocated by
+ * comedi_auto_config() for the same hardware device.  As part of this
+ * clean-up, the low-level COMEDI driver's 'detach' handler will be called.
+ * (The COMEDI device itself will persist in an unattached state if it is
+ * still open, until it is released, and any mmapped buffers will persist
+ * until they are munmapped.)
+ *
+ * This is usually called from a wrapper module in a bus-specific COMEDI
+ * module, which in turn is usually set as the bus device 'remove' function
+ * in the low-level COMEDI driver.
+ */
 void comedi_auto_unconfig(struct device *hardware_device)
 {
 	if (!hardware_device)
@@ -896,6 +1065,17 @@ void comedi_auto_unconfig(struct device *hardware_device)
 }
 EXPORT_SYMBOL_GPL(comedi_auto_unconfig);
 
+/**
+ * comedi_driver_register() - Register a low-level COMEDI driver
+ * @driver: Low-level COMEDI driver.
+ *
+ * The low-level COMEDI driver is added to the list of registered COMEDI
+ * drivers.  This is used by the handler for the "/proc/comedi" file and is
+ * also used by the handler for the %COMEDI_DEVCONFIG ioctl to configure
+ * "legacy" COMEDI devices (for those low-level drivers that support it).
+ *
+ * Returns 0.
+ */
 int comedi_driver_register(struct comedi_driver *driver)
 {
 	mutex_lock(&comedi_drivers_list_lock);
@@ -907,6 +1087,15 @@ int comedi_driver_register(struct comedi_driver *driver)
 }
 EXPORT_SYMBOL_GPL(comedi_driver_register);
 
+/**
+ * comedi_driver_unregister() - Unregister a low-level COMEDI driver
+ * @driver: Low-level COMEDI driver.
+ *
+ * The low-level COMEDI driver is removed from the list of registered COMEDI
+ * drivers.  Detaches any COMEDI devices attached to the driver, which will
+ * result in the low-level driver's 'detach' handler being called for those
+ * devices before this function returns.
+ */
 void comedi_driver_unregister(struct comedi_driver *driver)
 {
 	struct comedi_driver *prev;