alan at lxorguk
Jun 10, 2008, 4:27 AM
Post #4 of 4
(251 views)
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> Can anybody help me writing a small kernel-driver for this? I heard of
> the GPIO-framework, but I have no clue where to start with. I simply
> want to switch these ports to 0 or 1 :).
>
> I don't know under what license this documentation is, I simply got
> these 6 pages with sample source code.
This is a 5 minute hack on the Nat Semi Geode GPIO driver so you might
need to debug it a bit as its untested.
epiapd_gpio: driver for EPIA-PD
From: Alan Cox <alan [at] redhat>
This is a simple driver for the EPIA-PD GPIO lines
---
drivers/char/Kconfig | 6 +
drivers/char/Makefile | 1
drivers/char/epiapd_gpio.c | 182 ++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 189 insertions(+), 0 deletions(-)
create mode 100644 drivers/char/epiapd_gpio.c
diff --git a/drivers/char/Kconfig b/drivers/char/Kconfig
index 595a925..c308e15 100644
--- a/drivers/char/Kconfig
+++ b/drivers/char/Kconfig
@@ -932,6 +932,12 @@ config GPIO_TB0219
depends on TANBAC_TB022X
select GPIO_VR41XX
+config GPIO_EPIAPD
+ tristate "EPIA-PD VT8251 GPIO support"
+ ---help---
+ This driver provides access to the GPI/GPO pins on the VT8251
+ EPIA-PD board.
+
source "drivers/char/pcmcia/Kconfig"
config MWAVE
diff --git a/drivers/char/Makefile b/drivers/char/Makefile
index 4c1c584..237ebfc 100644
--- a/drivers/char/Makefile
+++ b/drivers/char/Makefile
@@ -96,6 +96,7 @@ obj-$(CONFIG_PC8736x_GPIO) += pc8736x_gpio.o
obj-$(CONFIG_NSC_GPIO) += nsc_gpio.o
obj-$(CONFIG_CS5535_GPIO) += cs5535_gpio.o
obj-$(CONFIG_GPIO_VR41XX) += vr41xx_giu.o
+obj-$(CONFIG_GPIO_EPIAPD) += epiapd_gpio.o
obj-$(CONFIG_GPIO_TB0219) += tb0219.o
obj-$(CONFIG_TELCLOCK) += tlclk.o
diff --git a/drivers/char/epiapd_gpio.c b/drivers/char/epiapd_gpio.c
new file mode 100644
index 0000000..eedb4ae
--- /dev/null
+++ b/drivers/char/epiapd_gpio.c
@@ -0,0 +1,182 @@
+/* linux/drivers/char/epiapd_gpio.c
+
+ EPIA-PD GPIO driver. Allows a user space process to play with the GPIO pins.
+
+ based on the Nat Semi GPIO driver
+ Copyright (c) 2001,2002 Christer Weinigel <wingel [at] nano-system>
+*/
+
+#include <linux/device.h>
+#include <linux/fs.h>
+#include <linux/module.h>
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/uaccess.h>
+#include <linux/io.h>
+#include <linux/pci.h>
+#include <linux/types.h>
+#include <linux/cdev.h>
+
+#define DRVNAME "epiapd_gpio"
+
+MODULE_AUTHOR("Alan Cox <alan [at] redhat>");
+MODULE_DESCRIPTION("EPIA PD VIA VT8251 GPIO Pin Driver");
+MODULE_LICENSE("GPL");
+
+static int major = 0; /* default to dynamic major */
+module_param(major, int, 0);
+MODULE_PARM_DESC(major, "Major device number");
+
+#define MAX_PINS 8
+
+static unsigned long pmio;
+
+static void epiapd_gpio_set(int m, int v)
+{
+ u8 r = inb(pmio + 0x4C);
+ r &= ~ (1 << m);
+ r |= (v << m);
+ outb(r, pmio + 0x4C);
+}
+
+ssize_t epiapd_gpio_write(struct file *file, const char __user *data,
+ size_t len, loff_t *ppos)
+{
+ unsigned m = iminor(file->f_path.dentry->d_inode);
+ size_t i;
+ int err = 0;
+
+ for (i = 0; i < len; ++i) {
+ char c;
+ if (get_user(c, data + i)) {
+ err = -EFAULT;
+ break;
+ }
+ switch (c) {
+ case '0':
+ epiapd_gpio_set(m, 0);
+ break;
+ case '1':
+ epiapd_gpio_set(m, 1);
+ break;
+ case '\n':
+ /* end of settings string, do nothing */
+ break;
+ default:
+ err = -EINVAL;
+ break;
+ }
+ }
+ if (err) {
+ if(i == 0)
+ return err;
+ else
+ return i;
+ }
+ return len;
+}
+
+ssize_t epiapd_gpio_read(struct file *file, char __user * buf,
+ size_t len, loff_t * ppos)
+{
+ unsigned m = iminor(file->f_path.dentry->d_inode);
+ u8 r;
+ u8 c = '0';
+
+ r = inb(pmio + 0x47) & 7;
+ r |= (inb(pmio + 0x49) & 1) << 3;
+
+ if (r & (1 << m))
+ c = '1';
+
+ if (put_user(c, buf))
+ return -EFAULT;
+ return 1;
+}
+
+static int epiapd_gpio_open(struct inode *inode, struct file *file)
+{
+ unsigned m = iminor(inode);
+ if (m >= MAX_PINS)
+ return -EINVAL;
+ return nonseekable_open(inode, file);
+}
+
+static int epiapd_gpio_release(struct inode *inode, struct file *file)
+{
+ return 0;
+}
+
+static const struct file_operations epiapd_gpio_fileops = {
+ .owner = THIS_MODULE,
+ .write = epiapd_gpio_write,
+ .read = epiapd_gpio_read,
+ .open = epiapd_gpio_open,
+ .release = epiapd_gpio_release,
+};
+
+static struct cdev epiapd_gpio_cdev; /* use 1 cdev for all pins */
+
+static int __init epiapd_gpio_configure(void)
+{
+ struct pci_dev *pdev = pci_get_device(PCI_VENDOR_ID_VIA,
+ PCI_DEVICE_ID_VIA_8251, NULL);
+ u32 v;
+ u8 r;
+ if (pdev == NULL)
+ return -ENODEV;
+ pci_read_config_dword(pdev, 0x8B, &v);
+ v &= 0xFFFE;
+ if (v == 0)
+ return -ENODEV;
+ pmio = v;
+
+ /* Program the GPIO direction bits */
+ pci_read_config_byte(pdev, 0xE4, &r);
+ r &= 0x08;
+ pci_write_config_byte(pdev, 0xE4, r);
+ pci_read_config_byte(pdev, 0x95, &r);
+ r |= 0x02;
+ pci_write_config_byte(pdev, 0x95, r);
+ pci_read_config_byte(pdev, 0xE4, &r);
+ r |= 0x06;
+ pci_write_config_byte(pdev, 0xE4, r);
+
+ pci_dev_put(pdev);
+ return 0;
+}
+
+static int __init epiapd_gpio_init(void)
+{
+ int rc;
+ dev_t devid;
+
+ if (epiapd_gpio_configure() < 0) {
+ printk(KERN_ERR DRVNAME ": no VT8251 gpio present\n");
+ return -ENODEV;
+ }
+
+ if (major) {
+ devid = MKDEV(major, 0);
+ rc = register_chrdev_region(devid, MAX_PINS, "epiapd_gpio");
+ } else {
+ rc = alloc_chrdev_region(&devid, 0, MAX_PINS, "epiapd_gpio");
+ major = MAJOR(devid);
+ }
+ if (rc < 0)
+ return rc;
+ cdev_init(&epiapd_gpio_cdev, &epiapd_gpio_fileops);
+ cdev_add(&epiapd_gpio_cdev, devid, MAX_PINS);
+ return 0; /* succeed */
+}
+
+static void __exit epiapd_gpio_cleanup(void)
+{
+ cdev_del(&epiapd_gpio_cdev);
+ /* cdev_put(&epiapd_gpio_cdev); */
+ unregister_chrdev_region(MKDEV(major, 0), MAX_PINS);
+}
+
+module_init(epiapd_gpio_init);
+module_exit(epiapd_gpio_cleanup);
--
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