comedi: Move the main COMEDI headers

Move the main COMEDI driver headers out of "drivers/comedi/" into new
directory "include/linux/comedi/".  These are "comedidev.h",
"comedilib.h", "comedi_pci.h", "comedi_pcmcia.h", and "comedi_usb.h".
Additionally, move the user-space API header "comedi.h" into
"include/uapi/linux/" and add "WITH Linux-syscall-note" to its
SPDX-License-Identifier.

Update the "COMEDI DRIVERS" section of the MAINTAINERS file to account
for these changes.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Link: https://lore.kernel.org/r/20211117120604.117740-2-abbotti@mev.co.uk
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

5 files changed, 1224 insertions, 0 deletions

diff --git a/include/linux/comedi/comedi_pci.h b/include/linux/comedi/comedi_pci.h
new file mode 100644
index 000000000000..2fb50663e3ed
--- /dev/null
+++ b/include/linux/comedi/comedi_pci.h
@@ -0,0 +1,56 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * comedi_pci.h
+ * header file for Comedi PCI drivers
+ *
+ * COMEDI - Linux Control and Measurement Device Interface
+ * Copyright (C) 1997-2000 David A. Schleef <ds@schleef.org>
+ */
+
+#ifndef _COMEDI_PCI_H
+#define _COMEDI_PCI_H
+
+#include <linux/pci.h>
+#include <linux/comedi/comedidev.h>
+
+/*
+ * PCI Vendor IDs not in <linux/pci_ids.h>
+ */
+#define PCI_VENDOR_ID_KOLTER		0x1001
+#define PCI_VENDOR_ID_ICP		0x104c
+#define PCI_VENDOR_ID_DT		0x1116
+#define PCI_VENDOR_ID_IOTECH		0x1616
+#define PCI_VENDOR_ID_CONTEC		0x1221
+#define PCI_VENDOR_ID_RTD		0x1435
+#define PCI_VENDOR_ID_HUMUSOFT		0x186c
+
+struct pci_dev *comedi_to_pci_dev(struct comedi_device *dev);
+
+int comedi_pci_enable(struct comedi_device *dev);
+void comedi_pci_disable(struct comedi_device *dev);
+void comedi_pci_detach(struct comedi_device *dev);
+
+int comedi_pci_auto_config(struct pci_dev *pcidev, struct comedi_driver *driver,
+			   unsigned long context);
+void comedi_pci_auto_unconfig(struct pci_dev *pcidev);
+
+int comedi_pci_driver_register(struct comedi_driver *comedi_driver,
+			       struct pci_driver *pci_driver);
+void comedi_pci_driver_unregister(struct comedi_driver *comedi_driver,
+				  struct pci_driver *pci_driver);
+
+/**
+ * module_comedi_pci_driver() - Helper macro for registering a comedi PCI driver
+ * @__comedi_driver: comedi_driver struct
+ * @__pci_driver: pci_driver struct
+ *
+ * Helper macro for comedi PCI drivers which do not do anything special
+ * in module init/exit. This eliminates a lot of boilerplate. Each
+ * module may only use this macro once, and calling it replaces
+ * module_init() and module_exit()
+ */
+#define module_comedi_pci_driver(__comedi_driver, __pci_driver) \
+	module_driver(__comedi_driver, comedi_pci_driver_register, \
+			comedi_pci_driver_unregister, &(__pci_driver))
+
+#endif /* _COMEDI_PCI_H */
diff --git a/include/linux/comedi/comedi_pcmcia.h b/include/linux/comedi/comedi_pcmcia.h
new file mode 100644
index 000000000000..a33dfb65b869
--- /dev/null
+++ b/include/linux/comedi/comedi_pcmcia.h
@@ -0,0 +1,48 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * comedi_pcmcia.h
+ * header file for Comedi PCMCIA drivers
+ *
+ * COMEDI - Linux Control and Measurement Device Interface
+ * Copyright (C) 1997-2000 David A. Schleef <ds@schleef.org>
+ */
+
+#ifndef _COMEDI_PCMCIA_H
+#define _COMEDI_PCMCIA_H
+
+#include <pcmcia/cistpl.h>
+#include <pcmcia/ds.h>
+#include <linux/comedi/comedidev.h>
+
+struct pcmcia_device *comedi_to_pcmcia_dev(struct comedi_device *dev);
+
+int comedi_pcmcia_enable(struct comedi_device *dev,
+			 int (*conf_check)(struct pcmcia_device *p_dev,
+					   void *priv_data));
+void comedi_pcmcia_disable(struct comedi_device *dev);
+
+int comedi_pcmcia_auto_config(struct pcmcia_device *link,
+			      struct comedi_driver *driver);
+void comedi_pcmcia_auto_unconfig(struct pcmcia_device *link);
+
+int comedi_pcmcia_driver_register(struct comedi_driver *comedi_driver,
+				  struct pcmcia_driver *pcmcia_driver);
+void comedi_pcmcia_driver_unregister(struct comedi_driver *comedi_driver,
+				     struct pcmcia_driver *pcmcia_driver);
+
+/**
+ * module_comedi_pcmcia_driver() - Helper macro for registering a comedi
+ * PCMCIA driver
+ * @__comedi_driver: comedi_driver struct
+ * @__pcmcia_driver: pcmcia_driver struct
+ *
+ * Helper macro for comedi PCMCIA drivers which do not do anything special
+ * in module init/exit. This eliminates a lot of boilerplate. Each
+ * module may only use this macro once, and calling it replaces
+ * module_init() and module_exit()
+ */
+#define module_comedi_pcmcia_driver(__comedi_driver, __pcmcia_driver) \
+	module_driver(__comedi_driver, comedi_pcmcia_driver_register, \
+			comedi_pcmcia_driver_unregister, &(__pcmcia_driver))
+
+#endif /* _COMEDI_PCMCIA_H */
diff --git a/include/linux/comedi/comedi_usb.h b/include/linux/comedi/comedi_usb.h
new file mode 100644
index 000000000000..5d17dd425bd2
--- /dev/null
+++ b/include/linux/comedi/comedi_usb.h
@@ -0,0 +1,41 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/* comedi_usb.h
+ * header file for USB Comedi drivers
+ *
+ * COMEDI - Linux Control and Measurement Device Interface
+ * Copyright (C) 1997-2000 David A. Schleef <ds@schleef.org>
+ */
+
+#ifndef _COMEDI_USB_H
+#define _COMEDI_USB_H
+
+#include <linux/usb.h>
+#include <linux/comedi/comedidev.h>
+
+struct usb_interface *comedi_to_usb_interface(struct comedi_device *dev);
+struct usb_device *comedi_to_usb_dev(struct comedi_device *dev);
+
+int comedi_usb_auto_config(struct usb_interface *intf,
+			   struct comedi_driver *driver, unsigned long context);
+void comedi_usb_auto_unconfig(struct usb_interface *intf);
+
+int comedi_usb_driver_register(struct comedi_driver *comedi_driver,
+			       struct usb_driver *usb_driver);
+void comedi_usb_driver_unregister(struct comedi_driver *comedi_driver,
+				  struct usb_driver *usb_driver);
+
+/**
+ * module_comedi_usb_driver() - Helper macro for registering a comedi USB driver
+ * @__comedi_driver: comedi_driver struct
+ * @__usb_driver: usb_driver struct
+ *
+ * Helper macro for comedi USB drivers which do not do anything special
+ * in module init/exit. This eliminates a lot of boilerplate. Each
+ * module may only use this macro once, and calling it replaces
+ * module_init() and module_exit()
+ */
+#define module_comedi_usb_driver(__comedi_driver, __usb_driver) \
+	module_driver(__comedi_driver, comedi_usb_driver_register, \
+			comedi_usb_driver_unregister, &(__usb_driver))
+
+#endif /* _COMEDI_USB_H */
diff --git a/include/linux/comedi/comedidev.h b/include/linux/comedi/comedidev.h
new file mode 100644
index 000000000000..0a1150900ef3
--- /dev/null
+++ b/include/linux/comedi/comedidev.h
@@ -0,0 +1,1053 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * comedidev.h
+ * header file for kernel-only structures, variables, and constants
+ *
+ * COMEDI - Linux Control and Measurement Device Interface
+ * Copyright (C) 1997-2000 David A. Schleef <ds@schleef.org>
+ */
+
+#ifndef _COMEDIDEV_H
+#define _COMEDIDEV_H
+
+#include <linux/dma-mapping.h>
+#include <linux/mutex.h>
+#include <linux/spinlock_types.h>
+#include <linux/rwsem.h>
+#include <linux/kref.h>
+#include <linux/comedi.h>
+
+#define COMEDI_VERSION(a, b, c) (((a) << 16) + ((b) << 8) + (c))
+#define COMEDI_VERSION_CODE COMEDI_VERSION(COMEDI_MAJORVERSION, \
+	COMEDI_MINORVERSION, COMEDI_MICROVERSION)
+#define COMEDI_RELEASE VERSION
+
+#define COMEDI_NUM_BOARD_MINORS 0x30
+
+/**
+ * struct comedi_subdevice - Working data for a COMEDI subdevice
+ * @device: COMEDI device to which this subdevice belongs.  (Initialized by
+ *	comedi_alloc_subdevices().)
+ * @index: Index of this subdevice within device's array of subdevices.
+ *	(Initialized by comedi_alloc_subdevices().)
+ * @type: Type of subdevice from &enum comedi_subdevice_type.  (Initialized by
+ *	the low-level driver.)
+ * @n_chan: Number of channels the subdevice supports.  (Initialized by the
+ *	low-level driver.)
+ * @subdev_flags: Various "SDF" flags indicating aspects of the subdevice to
+ *	the COMEDI core and user application.  (Initialized by the low-level
+ *	driver.)
+ * @len_chanlist: Maximum length of a channel list if the subdevice supports
+ *	asynchronous acquisition commands.  (Optionally initialized by the
+ *	low-level driver, or changed from 0 to 1 during post-configuration.)
+ * @private: Private data pointer which is either set by the low-level driver
+ *	itself, or by a call to comedi_alloc_spriv() which allocates storage.
+ *	In the latter case, the storage is automatically freed after the
+ *	low-level driver's "detach" handler is called for the device.
+ *	(Initialized by the low-level driver.)
+ * @async: Pointer to &struct comedi_async id the subdevice supports
+ *	asynchronous acquisition commands.  (Allocated and initialized during
+ *	post-configuration if needed.)
+ * @lock: Pointer to a file object that performed a %COMEDI_LOCK ioctl on the
+ *	subdevice.  (Initially NULL.)
+ * @busy: Pointer to a file object that is performing an asynchronous
+ *	acquisition command on the subdevice.  (Initially NULL.)
+ * @runflags: Internal flags for use by COMEDI core, mostly indicating whether
+ *	an asynchronous acquisition command is running.
+ * @spin_lock: Generic spin-lock for use by the COMEDI core and the low-level
+ *	driver.  (Initialized by comedi_alloc_subdevices().)
+ * @io_bits: Bit-mask indicating the channel directions for a DIO subdevice
+ *	with no more than 32 channels.  A '1' at a bit position indicates the
+ *	corresponding channel is configured as an output.  (Initialized by the
+ *	low-level driver for a DIO subdevice.  Forced to all-outputs during
+ *	post-configuration for a digital output subdevice.)
+ * @maxdata: If non-zero, this is the maximum raw data value of each channel.
+ *	If zero, the maximum data value is channel-specific.  (Initialized by
+ *	the low-level driver.)
+ * @maxdata_list: If the maximum data value is channel-specific, this points
+ *	to an array of maximum data values indexed by channel index.
+ *	(Initialized by the low-level driver.)
+ * @range_table: If non-NULL, this points to a COMEDI range table for the
+ *	subdevice.  If NULL, the range table is channel-specific.  (Initialized
+ *	by the low-level driver, will be set to an "invalid" range table during
+ *	post-configuration if @range_table and @range_table_list are both
+ *	NULL.)
+ * @range_table_list: If the COMEDI range table is channel-specific, this
+ *	points to an array of pointers to COMEDI range tables indexed by
+ *	channel number.  (Initialized by the low-level driver.)
+ * @chanlist: Not used.
+ * @insn_read: Optional pointer to a handler for the %INSN_READ instruction.
+ *	(Initialized by the low-level driver, or set to a default handler
+ *	during post-configuration.)
+ * @insn_write: Optional pointer to a handler for the %INSN_WRITE instruction.
+ *	(Initialized by the low-level driver, or set to a default handler
+ *	during post-configuration.)
+ * @insn_bits: Optional pointer to a handler for the %INSN_BITS instruction
+ *	for a digital input, digital output or digital input/output subdevice.
+ *	(Initialized by the low-level driver, or set to a default handler
+ *	during post-configuration.)
+ * @insn_config: Optional pointer to a handler for the %INSN_CONFIG
+ *	instruction.  (Initialized by the low-level driver, or set to a default
+ *	handler during post-configuration.)
+ * @do_cmd: If the subdevice supports asynchronous acquisition commands, this
+ *	points to a handler to set it up in hardware.  (Initialized by the
+ *	low-level driver.)
+ * @do_cmdtest: If the subdevice supports asynchronous acquisition commands,
+ *	this points to a handler used to check and possibly tweak a prospective
+ *	acquisition command without setting it up in hardware.  (Initialized by
+ *	the low-level driver.)
+ * @poll: If the subdevice supports asynchronous acquisition commands, this
+ *	is an optional pointer to a handler for the %COMEDI_POLL ioctl which
+ *	instructs the low-level driver to synchronize buffers.  (Initialized by
+ *	the low-level driver if needed.)
+ * @cancel: If the subdevice supports asynchronous acquisition commands, this
+ *	points to a handler used to terminate a running command.  (Initialized
+ *	by the low-level driver.)
+ * @buf_change: If the subdevice supports asynchronous acquisition commands,
+ *	this is an optional pointer to a handler that is called when the data
+ *	buffer for handling asynchronous commands is allocated or reallocated.
+ *	(Initialized by the low-level driver if needed.)
+ * @munge: If the subdevice supports asynchronous acquisition commands and
+ *	uses DMA to transfer data from the hardware to the acquisition buffer,
+ *	this points to a function used to "munge" the data values from the
+ *	hardware into the format expected by COMEDI.  (Initialized by the
+ *	low-level driver if needed.)
+ * @async_dma_dir: If the subdevice supports asynchronous acquisition commands
+ *	and uses DMA to transfer data from the hardware to the acquisition
+ *	buffer, this sets the DMA direction for the buffer. (initialized to
+ *	%DMA_NONE by comedi_alloc_subdevices() and changed by the low-level
+ *	driver if necessary.)
+ * @state: Handy bit-mask indicating the output states for a DIO or digital
+ *	output subdevice with no more than 32 channels. (Initialized by the
+ *	low-level driver.)
+ * @class_dev: If the subdevice supports asynchronous acquisition commands,
+ *	this points to a sysfs comediX_subdY device where X is the minor device
+ *	number of the COMEDI device and Y is the subdevice number.  The minor
+ *	device number for the sysfs device is allocated dynamically in the
+ *	range 48 to 255.  This is used to allow the COMEDI device to be opened
+ *	with a different default read or write subdevice.  (Allocated during
+ *	post-configuration if needed.)
+ * @minor: If @class_dev is set, this is its dynamically allocated minor
+ *	device number.  (Set during post-configuration if necessary.)
+ * @readback: Optional pointer to memory allocated by
+ *	comedi_alloc_subdev_readback() used to hold the values written to
+ *	analog output channels so they can be read back.  The storage is
+ *	automatically freed after the low-level driver's "detach" handler is
+ *	called for the device.  (Initialized by the low-level driver.)
+ *
+ * This is the main control structure for a COMEDI subdevice.  If the subdevice
+ * supports asynchronous acquisition commands, additional information is stored
+ * in the &struct comedi_async pointed to by @async.
+ *
+ * Most of the subdevice is initialized by the low-level driver's "attach" or
+ * "auto_attach" handlers but parts of it are initialized by
+ * comedi_alloc_subdevices(), and other parts are initialized during
+ * post-configuration on return from that handler.
+ *
+ * A low-level driver that sets @insn_bits for a digital input, digital output,
+ * or DIO subdevice may leave @insn_read and @insn_write uninitialized, in
+ * which case they will be set to a default handler during post-configuration
+ * that uses @insn_bits to emulate the %INSN_READ and %INSN_WRITE instructions.
+ */
+struct comedi_subdevice {
+	struct comedi_device *device;
+	int index;
+	int type;
+	int n_chan;
+	int subdev_flags;
+	int len_chanlist;	/* maximum length of channel/gain list */
+
+	void *private;
+
+	struct comedi_async *async;
+
+	void *lock;
+	void *busy;
+	unsigned int runflags;
+	spinlock_t spin_lock;	/* generic spin-lock for COMEDI and drivers */
+
+	unsigned int io_bits;
+
+	unsigned int maxdata;	/* if maxdata==0, use list */
+	const unsigned int *maxdata_list;	/* list is channel specific */
+
+	const struct comedi_lrange *range_table;
+	const struct comedi_lrange *const *range_table_list;
+
+	unsigned int *chanlist;	/* driver-owned chanlist (not used) */
+
+	int (*insn_read)(struct comedi_device *dev, struct comedi_subdevice *s,
+			 struct comedi_insn *insn, unsigned int *data);
+	int (*insn_write)(struct comedi_device *dev, struct comedi_subdevice *s,
+			  struct comedi_insn *insn, unsigned int *data);
+	int (*insn_bits)(struct comedi_device *dev, struct comedi_subdevice *s,
+			 struct comedi_insn *insn, unsigned int *data);
+	int (*insn_config)(struct comedi_device *dev,
+			   struct comedi_subdevice *s,
+			   struct comedi_insn *insn,
+			   unsigned int *data);
+
+	int (*do_cmd)(struct comedi_device *dev, struct comedi_subdevice *s);
+	int (*do_cmdtest)(struct comedi_device *dev,
+			  struct comedi_subdevice *s,
+			  struct comedi_cmd *cmd);
+	int (*poll)(struct comedi_device *dev, struct comedi_subdevice *s);
+	int (*cancel)(struct comedi_device *dev, struct comedi_subdevice *s);
+
+	/* called when the buffer changes */
+	int (*buf_change)(struct comedi_device *dev,
+			  struct comedi_subdevice *s);
+
+	void (*munge)(struct comedi_device *dev, struct comedi_subdevice *s,
+		      void *data, unsigned int num_bytes,
+		      unsigned int start_chan_index);
+	enum dma_data_direction async_dma_dir;
+
+	unsigned int state;
+
+	struct device *class_dev;
+	int minor;
+
+	unsigned int *readback;
+};
+
+/**
+ * struct comedi_buf_page - Describe a page of a COMEDI buffer
+ * @virt_addr: Kernel address of page.
+ * @dma_addr: DMA address of page if in DMA coherent memory.
+ */
+struct comedi_buf_page {
+	void *virt_addr;
+	dma_addr_t dma_addr;
+};
+
+/**
+ * struct comedi_buf_map - Describe pages in a COMEDI buffer
+ * @dma_hw_dev: Low-level hardware &struct device pointer copied from the
+ *	COMEDI device's hw_dev member.
+ * @page_list: Pointer to array of &struct comedi_buf_page, one for each
+ *	page in the buffer.
+ * @n_pages: Number of pages in the buffer.
+ * @dma_dir: DMA direction used to allocate pages of DMA coherent memory,
+ *	or %DMA_NONE if pages allocated from regular memory.
+ * @refcount: &struct kref reference counter used to free the buffer.
+ *
+ * A COMEDI data buffer is allocated as individual pages, either in
+ * conventional memory or DMA coherent memory, depending on the attached,
+ * low-level hardware device.  (The buffer pages also get mapped into the
+ * kernel's contiguous virtual address space pointed to by the 'prealloc_buf'
+ * member of &struct comedi_async.)
+ *
+ * The buffer is normally freed when the COMEDI device is detached from the
+ * low-level driver (which may happen due to device removal), but if it happens
+ * to be mmapped at the time, the pages cannot be freed until the buffer has
+ * been munmapped.  That is what the reference counter is for.  (The virtual
+ * address space pointed by 'prealloc_buf' is freed when the COMEDI device is
+ * detached.)
+ */
+struct comedi_buf_map {
+	struct device *dma_hw_dev;
+	struct comedi_buf_page *page_list;
+	unsigned int n_pages;
+	enum dma_data_direction dma_dir;
+	struct kref refcount;
+};
+
+/**
+ * struct comedi_async - Control data for asynchronous COMEDI commands
+ * @prealloc_buf: Kernel virtual address of allocated acquisition buffer.
+ * @prealloc_bufsz: Buffer size (in bytes).
+ * @buf_map: Map of buffer pages.
+ * @max_bufsize: Maximum allowed buffer size (in bytes).
+ * @buf_write_count: "Write completed" count (in bytes, modulo 2**32).
+ * @buf_write_alloc_count: "Allocated for writing" count (in bytes,
+ *	modulo 2**32).
+ * @buf_read_count: "Read completed" count (in bytes, modulo 2**32).
+ * @buf_read_alloc_count: "Allocated for reading" count (in bytes,
+ *	modulo 2**32).
+ * @buf_write_ptr: Buffer position for writer.
+ * @buf_read_ptr: Buffer position for reader.
+ * @cur_chan: Current position in chanlist for scan (for those drivers that
+ *	use it).
+ * @scans_done: The number of scans completed.
+ * @scan_progress: Amount received or sent for current scan (in bytes).
+ * @munge_chan: Current position in chanlist for "munging".
+ * @munge_count: "Munge" count (in bytes, modulo 2**32).
+ * @munge_ptr: Buffer position for "munging".
+ * @events: Bit-vector of events that have occurred.
+ * @cmd: Details of comedi command in progress.
+ * @wait_head: Task wait queue for file reader or writer.
+ * @cb_mask: Bit-vector of events that should wake waiting tasks.
+ * @inttrig: Software trigger function for command, or NULL.
+ *
+ * Note about the ..._count and ..._ptr members:
+ *
+ * Think of the _Count values being integers of unlimited size, indexing
+ * into a buffer of infinite length (though only an advancing portion
+ * of the buffer of fixed length prealloc_bufsz is accessible at any
+ * time).  Then:
+ *
+ *   Buf_Read_Count <= Buf_Read_Alloc_Count <= Munge_Count <=
+ *   Buf_Write_Count <= Buf_Write_Alloc_Count <=
+ *   (Buf_Read_Count + prealloc_bufsz)
+ *
+ * (Those aren't the actual members, apart from prealloc_bufsz.) When the
+ * buffer is reset, those _Count values start at 0 and only increase in value,
+ * maintaining the above inequalities until the next time the buffer is
+ * reset.  The buffer is divided into the following regions by the inequalities:
+ *
+ *   [0, Buf_Read_Count):
+ *     old region no longer accessible
+ *
+ *   [Buf_Read_Count, Buf_Read_Alloc_Count):
+ *     filled and munged region allocated for reading but not yet read
+ *
+ *   [Buf_Read_Alloc_Count, Munge_Count):
+ *     filled and munged region not yet allocated for reading
+ *
+ *   [Munge_Count, Buf_Write_Count):
+ *     filled region not yet munged
+ *
+ *   [Buf_Write_Count, Buf_Write_Alloc_Count):
+ *     unfilled region allocated for writing but not yet written
+ *
+ *   [Buf_Write_Alloc_Count, Buf_Read_Count + prealloc_bufsz):
+ *     unfilled region not yet allocated for writing
+ *
+ *   [Buf_Read_Count + prealloc_bufsz, infinity):
+ *     unfilled region not yet accessible
+ *
+ * Data needs to be written into the buffer before it can be read out,
+ * and may need to be converted (or "munged") between the two
+ * operations.  Extra unfilled buffer space may need to allocated for
+ * writing (advancing Buf_Write_Alloc_Count) before new data is written.
+ * After writing new data, the newly filled space needs to be released
+ * (advancing Buf_Write_Count).  This also results in the new data being
+ * "munged" (advancing Munge_Count).  Before data is read out of the
+ * buffer, extra space may need to be allocated for reading (advancing
+ * Buf_Read_Alloc_Count).  After the data has been read out, the space
+ * needs to be released (advancing Buf_Read_Count).
+ *
+ * The actual members, buf_read_count, buf_read_alloc_count,
+ * munge_count, buf_write_count, and buf_write_alloc_count take the
+ * value of the corresponding capitalized _Count values modulo 2^32
+ * (UINT_MAX+1).  Subtracting a "higher" _count value from a "lower"
+ * _count value gives the same answer as subtracting a "higher" _Count
+ * value from a lower _Count value because prealloc_bufsz < UINT_MAX+1.
+ * The modulo operation is done implicitly.
+ *
+ * The buf_read_ptr, munge_ptr, and buf_write_ptr members take the value
+ * of the corresponding capitalized _Count values modulo prealloc_bufsz.
+ * These correspond to byte indices in the physical buffer.  The modulo
+ * operation is done by subtracting prealloc_bufsz when the value
+ * exceeds prealloc_bufsz (assuming prealloc_bufsz plus the increment is
+ * less than or equal to UINT_MAX).
+ */
+struct comedi_async {
+	void *prealloc_buf;
+	unsigned int prealloc_bufsz;
+	struct comedi_buf_map *buf_map;
+	unsigned int max_bufsize;
+	unsigned int buf_write_count;
+	unsigned int buf_write_alloc_count;
+	unsigned int buf_read_count;
+	unsigned int buf_read_alloc_count;
+	unsigned int buf_write_ptr;
+	unsigned int buf_read_ptr;
+	unsigned int cur_chan;
+	unsigned int scans_done;
+	unsigned int scan_progress;
+	unsigned int munge_chan;
+	unsigned int munge_count;
+	unsigned int munge_ptr;
+	unsigned int events;
+	struct comedi_cmd cmd;
+	wait_queue_head_t wait_head;
+	unsigned int cb_mask;
+	int (*inttrig)(struct comedi_device *dev, struct comedi_subdevice *s,
+		       unsigned int x);
+};
+
+/**
+ * enum comedi_cb - &struct comedi_async callback "events"
+ * @COMEDI_CB_EOS:		end-of-scan
+ * @COMEDI_CB_EOA:		end-of-acquisition/output
+ * @COMEDI_CB_BLOCK:		data has arrived, wakes up read() / write()
+ * @COMEDI_CB_EOBUF:		DEPRECATED: end of buffer
+ * @COMEDI_CB_ERROR:		card error during acquisition
+ * @COMEDI_CB_OVERFLOW:		buffer overflow/underflow
+ * @COMEDI_CB_ERROR_MASK:	events that indicate an error has occurred
+ * @COMEDI_CB_CANCEL_MASK:	events that will cancel an async command
+ */
+enum comedi_cb {
+	COMEDI_CB_EOS		= BIT(0),
+	COMEDI_CB_EOA		= BIT(1),
+	COMEDI_CB_BLOCK		= BIT(2),
+	COMEDI_CB_EOBUF		= BIT(3),
+	COMEDI_CB_ERROR		= BIT(4),
+	COMEDI_CB_OVERFLOW	= BIT(5),
+	/* masks */
+	COMEDI_CB_ERROR_MASK	= (COMEDI_CB_ERROR | COMEDI_CB_OVERFLOW),
+	COMEDI_CB_CANCEL_MASK	= (COMEDI_CB_EOA | COMEDI_CB_ERROR_MASK)
+};
+
+/**
+ * struct comedi_driver - COMEDI driver registration
+ * @driver_name: Name of driver.
+ * @module: Owning module.
+ * @attach: The optional "attach" handler for manually configured COMEDI
+ *	devices.
+ * @detach: The "detach" handler for deconfiguring COMEDI devices.
+ * @auto_attach: The optional "auto_attach" handler for automatically
+ *	configured COMEDI devices.
+ * @num_names: Optional number of "board names" supported.
+ * @board_name: Optional pointer to a pointer to a board name.  The pointer
+ *	to a board name is embedded in an element of a driver-defined array
+ *	of static, read-only board type information.
+ * @offset: Optional size of each element of the driver-defined array of
+ *	static, read-only board type information, i.e. the offset between each
+ *	pointer to a board name.
+ *
+ * This is used with comedi_driver_register() and comedi_driver_unregister() to
+ * register and unregister a low-level COMEDI driver with the COMEDI core.
+ *
+ * If @num_names is non-zero, @board_name should be non-NULL, and @offset
+ * should be at least sizeof(*board_name).  These are used by the handler for
+ * the %COMEDI_DEVCONFIG ioctl to match a hardware device and its driver by
+ * board name.  If @num_names is zero, the %COMEDI_DEVCONFIG ioctl matches a
+ * hardware device and its driver by driver name.  This is only useful if the
+ * @attach handler is set.  If @num_names is non-zero, the driver's @attach
+ * handler will be called with the COMEDI device structure's board_ptr member
+ * pointing to the matched pointer to a board name within the driver's private
+ * array of static, read-only board type information.
+ *
+ * The @detach handler has two roles.  If a COMEDI device was successfully
+ * configured by the @attach or @auto_attach handler, it is called when the
+ * device is being deconfigured (by the %COMEDI_DEVCONFIG ioctl, or due to
+ * unloading of the driver, or due to device removal).  It is also called when
+ * the @attach or @auto_attach handler returns an error.  Therefore, the
+ * @attach or @auto_attach handlers can defer clean-up on error until the
+ * @detach handler is called.  If the @attach or @auto_attach handlers free
+ * any resources themselves, they must prevent the @detach handler from
+ * freeing the same resources.  The @detach handler must not assume that all
+ * resources requested by the @attach or @auto_attach handler were
+ * successfully allocated.
+ */
+struct comedi_driver {
+	/* private: */
+	struct comedi_driver *next;	/* Next in list of COMEDI drivers. */
+	/* public: */
+	const char *driver_name;
+	struct module *module;
+	int (*attach)(struct comedi_device *dev, struct comedi_devconfig *it);
+	void (*detach)(struct comedi_device *dev);
+	int (*auto_attach)(struct comedi_device *dev, unsigned long context);
+	unsigned int num_names;
+	const char *const *board_name;
+	int offset;
+};
+
+/**
+ * struct comedi_device - Working data for a COMEDI device
+ * @use_count: Number of open file objects.
+ * @driver: Low-level COMEDI driver attached to this COMEDI device.
+ * @pacer: Optional pointer to a dynamically allocated acquisition pacer
+ *	control.  It is freed automatically after the COMEDI device is
+ *	detached from the low-level driver.
+ * @private: Optional pointer to private data allocated by the low-level
+ *	driver.  It is freed automatically after the COMEDI device is
+ *	detached from the low-level driver.
+ * @class_dev: Sysfs comediX device.
+ * @minor: Minor device number of COMEDI char device (0-47).
+ * @detach_count: Counter incremented every time the COMEDI device is detached.
+ *	Used for checking a previous attachment is still valid.
+ * @hw_dev: Optional pointer to the low-level hardware &struct device.  It is
+ *	required for automatically configured COMEDI devices and optional for
+ *	COMEDI devices configured by the %COMEDI_DEVCONFIG ioctl, although
+ *	the bus-specific COMEDI functions only work if it is set correctly.
+ *	It is also passed to dma_alloc_coherent() for COMEDI subdevices that
+ *	have their 'async_dma_dir' member set to something other than
+ *	%DMA_NONE.
+ * @board_name: Pointer to a COMEDI board name or a COMEDI driver name.  When
+ *	the low-level driver's "attach" handler is called by the handler for
+ *	the %COMEDI_DEVCONFIG ioctl, it either points to a matched board name
+ *	string if the 'num_names' member of the &struct comedi_driver is
+ *	non-zero, otherwise it points to the low-level driver name string.
+ *	When the low-lever driver's "auto_attach" handler is called for an
+ *	automatically configured COMEDI device, it points to the low-level
+ *	driver name string.  The low-level driver is free to change it in its
+ *	"attach" or "auto_attach" handler if it wishes.
+ * @board_ptr: Optional pointer to private, read-only board type information in
+ *	the low-level driver.  If the 'num_names' member of the &struct
+ *	comedi_driver is non-zero, the handler for the %COMEDI_DEVCONFIG ioctl
+ *	will point it to a pointer to a matched board name string within the
+ *	driver's private array of static, read-only board type information when
+ *	calling the driver's "attach" handler.  The low-level driver is free to
+ *	change it.
+ * @attached: Flag indicating that the COMEDI device is attached to a low-level
+ *	driver.
+ * @ioenabled: Flag used to indicate that a PCI device has been enabled and
+ *	its regions requested.
+ * @spinlock: Generic spin-lock for use by the low-level driver.
+ * @mutex: Generic mutex for use by the COMEDI core module.
+ * @attach_lock: &struct rw_semaphore used to guard against the COMEDI device
+ *	being detached while an operation is in progress.  The down_write()
+ *	operation is only allowed while @mutex is held and is used when
+ *	changing @attached and @detach_count and calling the low-level driver's
+ *	"detach" handler.  The down_read() operation is generally used without
+ *	holding @mutex.
+ * @refcount: &struct kref reference counter for freeing COMEDI device.
+ * @n_subdevices: Number of COMEDI subdevices allocated by the low-level
+ *	driver for this device.
+ * @subdevices: Dynamically allocated array of COMEDI subdevices.
+ * @mmio: Optional pointer to a remapped MMIO region set by the low-level
+ *	driver.
+ * @iobase: Optional base of an I/O port region requested by the low-level
+ *	driver.
+ * @iolen: Length of I/O port region requested at @iobase.
+ * @irq: Optional IRQ number requested by the low-level driver.
+ * @read_subdev: Optional pointer to a default COMEDI subdevice operated on by
+ *	the read() file operation.  Set by the low-level driver.
+ * @write_subdev: Optional pointer to a default COMEDI subdevice operated on by
+ *	the write() file operation.  Set by the low-level driver.
+ * @async_queue: Storage for fasync_helper().
+ * @open: Optional pointer to a function set by the low-level driver to be
+ *	called when @use_count changes from 0 to 1.
+ * @close: Optional pointer to a function set by the low-level driver to be
+ *	called when @use_count changed from 1 to 0.
+ * @insn_device_config: Optional pointer to a handler for all sub-instructions
+ *	except %INSN_DEVICE_CONFIG_GET_ROUTES of the %INSN_DEVICE_CONFIG
+ *	instruction.  If this is not initialized by the low-level driver, a
+ *	default handler will be set during post-configuration.
+ * @get_valid_routes: Optional pointer to a handler for the
+ *	%INSN_DEVICE_CONFIG_GET_ROUTES sub-instruction of the
+ *	%INSN_DEVICE_CONFIG instruction set.  If this is not initialized by the
+ *	low-level driver, a default handler that copies zero routes back to the
+ *	user will be used.
+ *
+ * This is the main control data structure for a COMEDI device (as far as the
+ * COMEDI core is concerned).  There are two groups of COMEDI devices -
+ * "legacy" devices that are configured by the handler for the
+ * %COMEDI_DEVCONFIG ioctl, and automatically configured devices resulting
+ * from a call to comedi_auto_config() as a result of a bus driver probe in
+ * a low-level COMEDI driver.  The "legacy" COMEDI devices are allocated
+ * during module initialization if the "comedi_num_legacy_minors" module
+ * parameter is non-zero and use minor device numbers from 0 to
+ * comedi_num_legacy_minors minus one.  The automatically configured COMEDI
+ * devices are allocated on demand and use minor device numbers from
+ * comedi_num_legacy_minors to 47.
+ */
+struct comedi_device {
+	int use_count;
+	struct comedi_driver *driver;
+	struct comedi_8254 *pacer;
+	void *private;
+
+	struct device *class_dev;
+	int minor;
+	unsigned int detach_count;
+	struct device *hw_dev;
+
+	const char *board_name;
+	const void *board_ptr;
+	unsigned int attached:1;
+	unsigned int ioenabled:1;
+	spinlock_t spinlock;	/* generic spin-lock for low-level driver */
+	struct mutex mutex;	/* generic mutex for COMEDI core */
+	struct rw_semaphore attach_lock;
+	struct kref refcount;
+
+	int n_subdevices;
+	struct comedi_subdevice *subdevices;
+
+	/* dumb */
+	void __iomem *mmio;
+	unsigned long iobase;
+	unsigned long iolen;
+	unsigned int irq;
+
+	struct comedi_subdevice *read_subdev;
+	struct comedi_subdevice *write_subdev;
+
+	struct fasync_struct *async_queue;
+
+	int (*open)(struct comedi_device *dev);
+	void (*close)(struct comedi_device *dev);
+	int (*insn_device_config)(struct comedi_device *dev,
+				  struct comedi_insn *insn, unsigned int *data);
+	unsigned int (*get_valid_routes)(struct comedi_device *dev,
+					 unsigned int n_pairs,
+					 unsigned int *pair_data);
+};
+
+/*
+ * function prototypes
+ */
+
+void comedi_event(struct comedi_device *dev, struct comedi_subdevice *s);
+
+struct comedi_device *comedi_dev_get_from_minor(unsigned int minor);
+int comedi_dev_put(struct comedi_device *dev);
+
+bool comedi_is_subdevice_running(struct comedi_subdevice *s);
+
+void *comedi_alloc_spriv(struct comedi_subdevice *s, size_t size);
+void comedi_set_spriv_auto_free(struct comedi_subdevice *s);
+
+int comedi_check_chanlist(struct comedi_subdevice *s,
+			  int n,
+			  unsigned int *chanlist);
+
+/* range stuff */
+
+#define RANGE(a, b)		{(a) * 1e6, (b) * 1e6, 0}
+#define RANGE_ext(a, b)		{(a) * 1e6, (b) * 1e6, RF_EXTERNAL}
+#define RANGE_mA(a, b)		{(a) * 1e6, (b) * 1e6, UNIT_mA}
+#define RANGE_unitless(a, b)	{(a) * 1e6, (b) * 1e6, 0}
+#define BIP_RANGE(a)		{-(a) * 1e6, (a) * 1e6, 0}
+#define UNI_RANGE(a)		{0, (a) * 1e6, 0}
+
+extern const struct comedi_lrange range_bipolar10;
+extern const struct comedi_lrange range_bipolar5;
+extern const struct comedi_lrange range_bipolar2_5;
+extern const struct comedi_lrange range_unipolar10;
+extern const struct comedi_lrange range_unipolar5;
+extern const struct comedi_lrange range_unipolar2_5;
+extern const struct comedi_lrange range_0_20mA;
+extern const struct comedi_lrange range_4_20mA;
+extern const struct comedi_lrange range_0_32mA;
+extern const struct comedi_lrange range_unknown;
+
+#define range_digital		range_unipolar5
+
+/**
+ * struct comedi_lrange - Describes a COMEDI range table
+ * @length: Number of entries in the range table.
+ * @range: Array of &struct comedi_krange, one for each range.
+ *
+ * Each element of @range[] describes the minimum and maximum physical range
+ * and the type of units.  Typically, the type of unit is %UNIT_volt
+ * (i.e. volts) and the minimum and maximum are in millionths of a volt.
+ * There may also be a flag that indicates the minimum and maximum are merely
+ * scale factors for an unknown, external reference.
+ */
+struct comedi_lrange {
+	int length;
+	struct comedi_krange range[];
+};
+
+/**
+ * comedi_range_is_bipolar() - Test if subdevice range is bipolar
+ * @s: COMEDI subdevice.
+ * @range: Index of range within a range table.
+ *
+ * Tests whether a range is bipolar by checking whether its minimum value
+ * is negative.
+ *
+ * Assumes @range is valid.  Does not work for subdevices using a
+ * channel-specific range table list.
+ *
+ * Return:
+ *	%true if the range is bipolar.
+ *	%false if the range is unipolar.
+ */
+static inline bool comedi_range_is_bipolar(struct comedi_subdevice *s,
+					   unsigned int range)
+{
+	return s->range_table->range[range].min < 0;
+}
+
+/**
+ * comedi_range_is_unipolar() - Test if subdevice