/dev/spidevB.C interface

Add a filesystem API for <linux/spi/spi.h> stack.  The initial version of
this interface is purely synchronous.

dbrownell@users.sourceforge.net:

 Cleaned up, bugfixed; much simplified; added preliminary documentation.

 Works with mdev given CONFIG_SYSFS_DEPRECATED; and presumably udev.

 Updated SPI_IOC_MESSAGE ioctl to full spi_message semantics, supporting
 groups of one or more transfers (each of which may be full duplex if
 desired).

 This is marked as EXPERIMENTAL with an explicit disclaimer that the API
 (notably the ioctls) is subject to change.

Signed-off-by: Andrea Paterniani <a.paterniani@swapp-eng.it>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 125 insertions, 0 deletions

diff --git a/include/linux/spi/Kbuild b/include/linux/spi/Kbuild
new file mode 100644
index 000000000000..d375a082986e
--- /dev/null
+++ b/include/linux/spi/Kbuild
@@ -0,0 +1 @@
+header-y += spidev.h
diff --git a/include/linux/spi/spidev.h b/include/linux/spi/spidev.h
new file mode 100644
index 000000000000..7d700be57490
--- /dev/null
+++ b/include/linux/spi/spidev.h
@@ -0,0 +1,124 @@
+/*
+ * include/linux/spi/spidev.h
+ *
+ * Copyright (C) 2006 SWAPP
+ *	Andrea Paterniani <a.paterniani@swapp-eng.it>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+  */
+
+#ifndef SPIDEV_H
+#define SPIDEV_H
+
+
+/* User space versions of kernel symbols for SPI clocking modes,
+ * matching <linux/spi/spi.h>
+ */
+
+#define SPI_CPHA		0x01
+#define SPI_CPOL		0x02
+
+#define SPI_MODE_0		(0|0)
+#define SPI_MODE_1		(0|SPI_CPHA)
+#define SPI_MODE_2		(SPI_CPOL|0)
+#define SPI_MODE_3		(SPI_CPOL|SPI_CPHA)
+
+
+/*---------------------------------------------------------------------------*/
+
+/* IOCTL commands */
+
+#define SPI_IOC_MAGIC			'k'
+
+/**
+ * struct spi_ioc_transfer - describes a single SPI transfer
+ * @tx_buf: Holds pointer to userspace buffer with transmit data, or null.
+ *	If no data is provided, zeroes are shifted out.
+ * @rx_buf: Holds pointer to userspace buffer for receive data, or null.
+ * @len: Length of tx and rx buffers, in bytes.
+ * @speed_hz: Temporary override of the device's bitrate.
+ * @bits_per_word: Temporary override of the device's wordsize.
+ * @delay_usecs: If nonzero, how long to delay after the last bit transfer
+ *	before optionally deselecting the device before the next transfer.
+ * @cs_change: True to deselect device before starting the next transfer.
+ *
+ * This structure is mapped directly to the kernel spi_transfer structure;
+ * the fields have the same meanings, except of course that the pointers
+ * are in a different address space (and may be of different sizes in some
+ * cases, such as 32-bit i386 userspace over a 64-bit x86_64 kernel).
+ * Zero-initialize the structure, including currently unused fields, to
+ * accomodate potential future updates.
+ *
+ * SPI_IOC_MESSAGE gives userspace the equivalent of kernel spi_sync().
+ * Pass it an array of related transfers, they'll execute together.
+ * Each transfer may be half duplex (either direction) or full duplex.
+ *
+ *	struct spi_ioc_transfer mesg[4];
+ *	...
+ *	status = ioctl(fd, SPI_IOC_MESSAGE(4), mesg);
+ *
+ * So for example one transfer might send a nine bit command (right aligned
+ * in a 16-bit word), the next could read a block of 8-bit data before
+ * terminating that command by temporarily deselecting the chip; the next
+ * could send a different nine bit command (re-selecting the chip), and the
+ * last transfer might write some register values.
+ */
+struct spi_ioc_transfer {
+	__u64		tx_buf;
+	__u64		rx_buf;
+
+	__u32		len;
+	__u32		speed_hz;
+
+	__u16		delay_usecs;
+	__u8		bits_per_word;
+	__u8		cs_change;
+	__u32		pad;
+
+	/* If the contents of 'struct spi_ioc_transfer' ever change
+	 * incompatibly, then the ioctl number (currently 0) must change;
+	 * ioctls with constant size fields get a bit more in the way of
+	 * error checking than ones (like this) where that field varies.
+	 *
+	 * NOTE: struct layout is the same in 64bit and 32bit userspace.
+	 */
+};
+
+/* not all platforms use <asm-generic/ioctl.h> or _IOC_TYPECHECK() ... */
+#define SPI_MSGSIZE(N) \
+	((((N)*(sizeof (struct spi_ioc_transfer))) < (1 << _IOC_SIZEBITS)) \
+		? ((N)*(sizeof (struct spi_ioc_transfer))) : 0)
+#define SPI_IOC_MESSAGE(N) _IOW(SPI_IOC_MAGIC, 0, char[SPI_MSGSIZE(N)])
+
+
+/* Read / Write of SPI mode (SPI_MODE_0..SPI_MODE_3) */
+#define SPI_IOC_RD_MODE			_IOR(SPI_IOC_MAGIC, 1, __u8)
+#define SPI_IOC_WR_MODE			_IOW(SPI_IOC_MAGIC, 1, __u8)
+
+/* Read / Write SPI bit justification */
+#define SPI_IOC_RD_LSB_FIRST		_IOR(SPI_IOC_MAGIC, 2, __u8)
+#define SPI_IOC_WR_LSB_FIRST		_IOW(SPI_IOC_MAGIC, 2, __u8)
+
+/* Read / Write SPI device word length (1..N) */
+#define SPI_IOC_RD_BITS_PER_WORD	_IOR(SPI_IOC_MAGIC, 3, __u8)
+#define SPI_IOC_WR_BITS_PER_WORD	_IOW(SPI_IOC_MAGIC, 3, __u8)
+
+/* Read / Write SPI device default max speed hz */
+#define SPI_IOC_RD_MAX_SPEED_HZ		_IOR(SPI_IOC_MAGIC, 4, __u32)
+#define SPI_IOC_WR_MAX_SPEED_HZ		_IOW(SPI_IOC_MAGIC, 4, __u32)
+
+
+
+#endif /* SPIDEV_H */