package/kernel: add spi-gpio-custom module

The package makes it possible to create custom SPI
buses via GPIO lines.

This module is based on i2c-gpio-custom and allows to
configure an SPI bus via GPIO lines and expose it to
userspace without rebuilding the kernel. This is maily
intended to connect microcontrollers and other simple
SPI devices without making an ad-hoc kernel driver.

Signed-off-by: Marco Burato <zmaster.adsl@gmail.com>
[juhosg:
  - change subject,
  - extend and reformat commit message,
  - cleanup checkpatch errors/warnings in module source]
Signed-off-by: Gabor Juhos <juhosg@openwrt.org>

SVN-Revision: 37872

1 files changed, 365 insertions, 0 deletions

diff --git a/package/kernel/spi-gpio-custom/src/spi-gpio-custom.c b/package/kernel/spi-gpio-custom/src/spi-gpio-custom.c
new file mode 100644
index 0000000000..a4f93c67c2
--- /dev/null
+++ b/package/kernel/spi-gpio-custom/src/spi-gpio-custom.c
@@ -0,0 +1,365 @@
+/*
+ *  Custom GPIO-based SPI driver
+ *
+ *  Copyright (C) 2013 Marco Burato <zmaster.adsl@gmail.com>
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License version 2 as
+ *  published by the Free Software Foundation.
+ *
+ *  Based on i2c-gpio-custom by:
+ *  Copyright (C) 2007-2008 Gabor Juhos <juhosg@openwrt.org>
+ * ---------------------------------------------------------------------------
+ *
+ *  The behaviour of this driver can be altered by setting some parameters
+ *  from the insmod command line.
+ *
+ *  The following parameters are adjustable:
+ *
+ *	bus0	These four arguments can be arrays of
+ *	bus1	1-8 unsigned integers as follows:
+ *	bus2
+ *	bus3	<id>,<sck>,<mosi>,<miso>,<mode1>,<maxfreq1>,<cs1>,...
+ *
+ *  where:
+ *
+ *  <id>	ID to used as device_id for the corresponding bus (required)
+ *  <sck>	GPIO pin ID to be used for bus SCK (required)
+ *  <mosi>	GPIO pin ID to be used for bus MOSI (required*)
+ *  <miso>	GPIO pin ID to be used for bus MISO (required*)
+ *  <modeX>	Mode configuration for slave X in the bus (required)
+ *		(see /include/linux/spi/spi.h)
+ *  <maxfreqX>	Maximum clock frequency in Hz for slave X in the bus (required)
+ *  <csX>	GPIO pin ID to be used for slave X CS (required**)
+ *
+ *	Notes:
+ *	*	If a signal is not used (for example there is no MISO) you need
+ *		to set the GPIO pin ID for that signal to an invalid value.
+ *	**	If you only have 1 slave in the bus with no CS, you can omit the
+ *		<cs1> param or set it to an invalid GPIO id to disable it. When
+ *		you have 2 or more slaves, they must all have a valid CS.
+ *
+ *  If this driver is built into the kernel, you can use the following kernel
+ *  command line parameters, with the same values as the corresponding module
+ *  parameters listed above:
+ *
+ *	spi-gpio-custom.bus0
+ *	spi-gpio-custom.bus1
+ *	spi-gpio-custom.bus2
+ *	spi-gpio-custom.bus3
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/platform_device.h>
+
+#include <linux/gpio.h>
+#include <linux/spi/spi.h>
+#include <linux/spi/spi_gpio.h>
+
+#define DRV_NAME	"spi-gpio-custom"
+#define DRV_DESC	"Custom GPIO-based SPI driver"
+#define DRV_VERSION	"0.1"
+
+#define PFX		DRV_NAME ": "
+
+#define BUS_PARAM_ID		0
+#define BUS_PARAM_SCK		1
+#define BUS_PARAM_MOSI		2
+#define BUS_PARAM_MISO		3
+#define BUS_PARAM_MODE1		4
+#define BUS_PARAM_MAXFREQ1	5
+#define BUS_PARAM_CS1		6
+
+#define BUS_SLAVE_COUNT_MAX	8
+#define BUS_PARAM_REQUIRED	6
+#define BUS_PARAM_PER_SLAVE	3
+#define BUS_PARAM_COUNT		(4+BUS_PARAM_PER_SLAVE*BUS_SLAVE_COUNT_MAX)
+#define BUS_COUNT_MAX		4
+
+static unsigned int bus0[BUS_PARAM_COUNT] __initdata;
+static unsigned int bus1[BUS_PARAM_COUNT] __initdata;
+static unsigned int bus2[BUS_PARAM_COUNT] __initdata;
+static unsigned int bus3[BUS_PARAM_COUNT] __initdata;
+
+static unsigned int bus_nump[BUS_COUNT_MAX] __initdata;
+
+#define BUS_PARM_DESC \
+	" config -> id,sck,mosi,miso,mode1,maxfreq1[,cs1,mode2,maxfreq2,cs2,...]"
+
+module_param_array(bus0, uint, &bus_nump[0], 0);
+MODULE_PARM_DESC(bus0, "bus0" BUS_PARM_DESC);
+module_param_array(bus1, uint, &bus_nump[1], 0);
+MODULE_PARM_DESC(bus1, "bus1" BUS_PARM_DESC);
+module_param_array(bus2, uint, &bus_nump[2], 0);
+MODULE_PARM_DESC(bus2, "bus2" BUS_PARM_DESC);
+module_param_array(bus3, uint, &bus_nump[3], 0);
+MODULE_PARM_DESC(bus3, "bus3" BUS_PARM_DESC);
+
+static struct platform_device *devices[BUS_COUNT_MAX];
+static unsigned int nr_devices;
+
+static void spi_gpio_custom_cleanup(void)
+{
+	int i;
+
+	for (i = 0; i < nr_devices; i++)
+		if (devices[i])
+			platform_device_unregister(devices[i]);
+}
+
+static int spi_gpio_custom_get_slave_mode(unsigned int id,
+					  unsigned int *params,
+					  int slave_index)
+{
+	int param_index;
+
+	param_index = BUS_PARAM_MODE1+slave_index*BUS_PARAM_PER_SLAVE;
+	if (param_index >= bus_nump[id])
+		return -1;
+
+	return params[param_index];
+}
+static int spi_gpio_custom_get_slave_maxfreq(unsigned int id,
+					     unsigned int *params,
+					     int slave_index)
+{
+	int param_index;
+
+	param_index = BUS_PARAM_MAXFREQ1+slave_index*BUS_PARAM_PER_SLAVE;
+	if (param_index >= bus_nump[id])
+		return -1;
+
+	return params[param_index];
+}
+static int spi_gpio_custom_get_slave_cs(unsigned int id,
+					unsigned int *params,
+					int slave_index)
+{
+	int param_index;
+
+	param_index = BUS_PARAM_CS1+slave_index*BUS_PARAM_PER_SLAVE;
+	if (param_index >= bus_nump[id])
+		return -1;
+	if (!gpio_is_valid(params[param_index]))
+		return -1;
+
+	return params[param_index];
+}
+
+static int spi_gpio_custom_check_params(unsigned int id, unsigned int *params)
+{
+	int i;
+	struct spi_master *master;
+
+	if (bus_nump[id] < BUS_PARAM_REQUIRED) {
+		printk(KERN_ERR PFX "not enough values for parameter bus%d\n",
+		       id);
+		return -EINVAL;
+	}
+
+	if (bus_nump[id] > (1+BUS_PARAM_CS1)) {
+		/* more than 1 device: check CS GPIOs */
+		for (i = 0; i < BUS_SLAVE_COUNT_MAX; i++) {
+			/* no more slaves? */
+			if (spi_gpio_custom_get_slave_mode(id, params, i) < 0)
+				break;
+
+			if (spi_gpio_custom_get_slave_cs(id, params, i) < 0) {
+				printk(KERN_ERR PFX "invalid/missing CS gpio for slave %d on bus %d\n",
+				       i, params[BUS_PARAM_ID]);
+				return -EINVAL;
+			}
+		}
+	}
+
+	if (!gpio_is_valid(params[BUS_PARAM_SCK])) {
+		printk(KERN_ERR PFX "invalid SCK gpio for bus %d\n",
+		       params[BUS_PARAM_ID]);
+		return -EINVAL;
+	}
+
+	master = spi_busnum_to_master(params[BUS_PARAM_ID]);
+	if (master) {
+		spi_master_put(master);
+		printk(KERN_ERR PFX "bus %d already exists\n",
+		       params[BUS_PARAM_ID]);
+		return -EEXIST;
+	}
+
+	return 0;
+}
+
+static int __init spi_gpio_custom_add_one(unsigned int id, unsigned int *params)
+{
+	struct platform_device *pdev;
+	struct spi_gpio_platform_data pdata;
+	int i;
+	int num_cs;
+	int err;
+	struct spi_master *master;
+	struct spi_device *slave;
+	struct spi_board_info slave_info;
+	int mode, maxfreq, cs;
+
+
+	if (!bus_nump[id])
+		return 0;
+
+	err = spi_gpio_custom_check_params(id, params);
+	if (err)
+		goto err;
+
+	/* Create BUS device node */
+
+	pdev = platform_device_alloc("spi_gpio", params[BUS_PARAM_ID]);
+	if (!pdev) {
+		err = -ENOMEM;
+		goto err;
+	}
+
+	num_cs = 0;
+	for (i = 0; i < BUS_SLAVE_COUNT_MAX; i++) {
+		/* no more slaves? */
+		if (spi_gpio_custom_get_slave_mode(id, params, i) < 0)
+			break;
+
+		if (spi_gpio_custom_get_slave_cs(id, params, i) >= 0)
+			num_cs++;
+	}
+	if (num_cs == 0) {
+		/*
+		 * Even if no CS is used, spi modules expect
+		 * at least 1 (unused)
+		 */
+		num_cs = 1;
+	}
+
+	pdata.sck = params[BUS_PARAM_SCK];
+	pdata.mosi = gpio_is_valid(params[BUS_PARAM_MOSI])
+		? params[BUS_PARAM_MOSI]
+		: SPI_GPIO_NO_MOSI;
+	pdata.miso = gpio_is_valid(params[BUS_PARAM_MISO])
+		? params[BUS_PARAM_MISO]
+		: SPI_GPIO_NO_MISO;
+	pdata.num_chipselect = num_cs;
+
+	err = platform_device_add_data(pdev, &pdata, sizeof(pdata));
+	if (err) {
+		platform_device_put(pdev);
+		goto err;
+	}
+
+	err = platform_device_add(pdev);
+	if (err) {
+		printk(KERN_ERR PFX "platform_device_add failed with return code %d\n",
+		       err);
+		platform_device_put(pdev);
+		goto err;
+	}
+
+	/* Register SLAVE devices */
+
+	for (i = 0; i < BUS_SLAVE_COUNT_MAX; i++) {
+		mode = spi_gpio_custom_get_slave_mode(id, params, i);
+		maxfreq = spi_gpio_custom_get_slave_maxfreq(id, params, i);
+		cs = spi_gpio_custom_get_slave_cs(id, params, i);
+
+		/* no more slaves? */
+		if (mode < 0)
+			break;
+
+		memset(&slave_info, 0, sizeof(slave_info));
+		strcpy(slave_info.modalias, "spidev");
+		slave_info.controller_data = (void *)((cs >= 0)
+			? cs
+			: SPI_GPIO_NO_CHIPSELECT);
+		slave_info.max_speed_hz = maxfreq;
+		slave_info.bus_num = params[BUS_PARAM_ID];
+		slave_info.chip_select = i;
+		slave_info.mode = mode;
+
+		master = spi_busnum_to_master(params[BUS_PARAM_ID]);
+		if (!master) {
+			printk(KERN_ERR PFX "unable to get master for bus %d\n",
+			       params[BUS_PARAM_ID]);
+			err = -EINVAL;
+			goto err_unregister;
+		}
+		slave = spi_new_device(master, &slave_info);
+		spi_master_put(master);
+		if (!slave) {
+			printk(KERN_ERR PFX "unable to create slave %d for bus %d\n",
+			       i, params[BUS_PARAM_ID]);
+			/* Will most likely fail due to unsupported mode bits */
+			err = -EINVAL;
+			goto err_unregister;
+		}
+	}
+
+	devices[nr_devices++] = pdev;
+
+	return 0;
+
+err_unregister:
+	platform_device_unregister(pdev);
+err:
+	return err;
+}
+
+static int __init spi_gpio_custom_probe(void)
+{
+	int err;
+
+	printk(KERN_INFO DRV_DESC " version " DRV_VERSION "\n");
+
+	err = spi_gpio_custom_add_one(0, bus0);
+	if (err)
+		goto err;
+
+	err = spi_gpio_custom_add_one(1, bus1);
+	if (err)
+		goto err;
+
+	err = spi_gpio_custom_add_one(2, bus2);
+	if (err)
+		goto err;
+
+	err = spi_gpio_custom_add_one(3, bus3);
+	if (err)
+		goto err;
+
+	if (!nr_devices) {
+		printk(KERN_ERR PFX "no bus parameter(s) specified\n");
+		err = -ENODEV;
+		goto err;
+	}
+
+	return 0;
+
+err:
+	spi_gpio_custom_cleanup();
+	return err;
+}
+
+#ifdef MODULE
+static int __init spi_gpio_custom_init(void)
+{
+	return spi_gpio_custom_probe();
+}
+module_init(spi_gpio_custom_init);
+
+static void __exit spi_gpio_custom_exit(void)
+{
+	spi_gpio_custom_cleanup();
+}
+module_exit(spi_gpio_custom_exit);
+#else
+subsys_initcall(spi_gpio_custom_probe);
+#endif /* MODULE*/
+
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Marco Burato <zmaster.adsl@gmail.com>");
+MODULE_DESCRIPTION(DRV_DESC);
+MODULE_VERSION(DRV_VERSION);