linux/drivers/i2c/busses/i2c-parport-light.c
David Howells c78babcc7d Annotate hardware config module parameters in drivers/i2c/
When the kernel is running in secure boot mode, we lock down the kernel to
prevent userspace from modifying the running kernel image.  Whilst this
includes prohibiting access to things like /dev/mem, it must also prevent
access by means of configuring driver modules in such a way as to cause a
device to access or modify the kernel image.

To this end, annotate module_param* statements that refer to hardware
configuration and indicate for future reference what type of parameter they
specify.  The parameter parser in the core sees this information and can
skip such parameters with an error message if the kernel is locked down.
The module initialisation then runs as normal, but just sees whatever the
default values for those parameters is.

Note that we do still need to do the module initialisation because some
drivers have viable defaults set in case parameters aren't specified and
some drivers support automatic configuration (e.g. PNP or PCI) in addition
to manually coded parameters.

This patch annotates drivers in drivers/i2c/.

Suggested-by: Alan Cox <gnomes@lxorguk.ukuu.org.uk>
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Wolfram Sang <wsa@the-dreams.de>
Acked-by: Jean Delvare <jdelvare@suse.de>
cc: linux-i2c@vger.kernel.org
2017-04-20 12:02:32 +01:00

277 lines
6.6 KiB
C

/* ------------------------------------------------------------------------ *
* i2c-parport-light.c I2C bus over parallel port *
* ------------------------------------------------------------------------ *
Copyright (C) 2003-2010 Jean Delvare <jdelvare@suse.de>
Based on older i2c-velleman.c driver
Copyright (C) 1995-2000 Simon G. Vogl
With some changes from:
Frodo Looijaard <frodol@dds.nl>
Kyösti Mälkki <kmalkki@cc.hut.fi>
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.
* ------------------------------------------------------------------------ */
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/platform_device.h>
#include <linux/ioport.h>
#include <linux/i2c.h>
#include <linux/i2c-algo-bit.h>
#include <linux/i2c-smbus.h>
#include <linux/io.h>
#include "i2c-parport.h"
#define DEFAULT_BASE 0x378
#define DRVNAME "i2c-parport-light"
static struct platform_device *pdev;
static u16 base;
module_param_hw(base, ushort, ioport, 0);
MODULE_PARM_DESC(base, "Base I/O address");
static int irq;
module_param_hw(irq, int, irq, 0);
MODULE_PARM_DESC(irq, "IRQ (optional)");
/* ----- Low-level parallel port access ----------------------------------- */
static inline void port_write(unsigned char p, unsigned char d)
{
outb(d, base+p);
}
static inline unsigned char port_read(unsigned char p)
{
return inb(base+p);
}
/* ----- Unified line operation functions --------------------------------- */
static inline void line_set(int state, const struct lineop *op)
{
u8 oldval = port_read(op->port);
/* Touch only the bit(s) needed */
if ((op->inverted && !state) || (!op->inverted && state))
port_write(op->port, oldval | op->val);
else
port_write(op->port, oldval & ~op->val);
}
static inline int line_get(const struct lineop *op)
{
u8 oldval = port_read(op->port);
return ((op->inverted && (oldval & op->val) != op->val)
|| (!op->inverted && (oldval & op->val) == op->val));
}
/* ----- I2C algorithm call-back functions and structures ----------------- */
static void parport_setscl(void *data, int state)
{
line_set(state, &adapter_parm[type].setscl);
}
static void parport_setsda(void *data, int state)
{
line_set(state, &adapter_parm[type].setsda);
}
static int parport_getscl(void *data)
{
return line_get(&adapter_parm[type].getscl);
}
static int parport_getsda(void *data)
{
return line_get(&adapter_parm[type].getsda);
}
/* Encapsulate the functions above in the correct structure
Note that getscl will be set to NULL by the attaching code for adapters
that cannot read SCL back */
static struct i2c_algo_bit_data parport_algo_data = {
.setsda = parport_setsda,
.setscl = parport_setscl,
.getsda = parport_getsda,
.getscl = parport_getscl,
.udelay = 50,
.timeout = HZ,
};
/* ----- Driver registration ---------------------------------------------- */
static struct i2c_adapter parport_adapter = {
.owner = THIS_MODULE,
.class = I2C_CLASS_HWMON,
.algo_data = &parport_algo_data,
.name = "Parallel port adapter (light)",
};
/* SMBus alert support */
static struct i2c_smbus_alert_setup alert_data = {
.alert_edge_triggered = 1,
};
static struct i2c_client *ara;
static struct lineop parport_ctrl_irq = {
.val = (1 << 4),
.port = PORT_CTRL,
};
static int i2c_parport_probe(struct platform_device *pdev)
{
int err;
/* Reset hardware to a sane state (SCL and SDA high) */
parport_setsda(NULL, 1);
parport_setscl(NULL, 1);
/* Other init if needed (power on...) */
if (adapter_parm[type].init.val) {
line_set(1, &adapter_parm[type].init);
/* Give powered devices some time to settle */
msleep(100);
}
parport_adapter.dev.parent = &pdev->dev;
err = i2c_bit_add_bus(&parport_adapter);
if (err) {
dev_err(&pdev->dev, "Unable to register with I2C\n");
return err;
}
/* Setup SMBus alert if supported */
if (adapter_parm[type].smbus_alert && irq) {
alert_data.irq = irq;
ara = i2c_setup_smbus_alert(&parport_adapter, &alert_data);
if (ara)
line_set(1, &parport_ctrl_irq);
else
dev_warn(&pdev->dev, "Failed to register ARA client\n");
}
return 0;
}
static int i2c_parport_remove(struct platform_device *pdev)
{
if (ara) {
line_set(0, &parport_ctrl_irq);
i2c_unregister_device(ara);
ara = NULL;
}
i2c_del_adapter(&parport_adapter);
/* Un-init if needed (power off...) */
if (adapter_parm[type].init.val)
line_set(0, &adapter_parm[type].init);
return 0;
}
static struct platform_driver i2c_parport_driver = {
.driver = {
.name = DRVNAME,
},
.probe = i2c_parport_probe,
.remove = i2c_parport_remove,
};
static int __init i2c_parport_device_add(u16 address)
{
int err;
pdev = platform_device_alloc(DRVNAME, -1);
if (!pdev) {
err = -ENOMEM;
printk(KERN_ERR DRVNAME ": Device allocation failed\n");
goto exit;
}
err = platform_device_add(pdev);
if (err) {
printk(KERN_ERR DRVNAME ": Device addition failed (%d)\n",
err);
goto exit_device_put;
}
return 0;
exit_device_put:
platform_device_put(pdev);
exit:
return err;
}
static int __init i2c_parport_init(void)
{
int err;
if (type < 0) {
printk(KERN_ERR DRVNAME ": adapter type unspecified\n");
return -ENODEV;
}
if (type >= ARRAY_SIZE(adapter_parm)) {
printk(KERN_ERR DRVNAME ": invalid type (%d)\n", type);
return -ENODEV;
}
if (base == 0) {
pr_info(DRVNAME ": using default base 0x%x\n", DEFAULT_BASE);
base = DEFAULT_BASE;
}
if (!request_region(base, 3, DRVNAME))
return -EBUSY;
if (irq != 0)
pr_info(DRVNAME ": using irq %d\n", irq);
if (!adapter_parm[type].getscl.val)
parport_algo_data.getscl = NULL;
/* Sets global pdev as a side effect */
err = i2c_parport_device_add(base);
if (err)
goto exit_release;
err = platform_driver_register(&i2c_parport_driver);
if (err)
goto exit_device;
return 0;
exit_device:
platform_device_unregister(pdev);
exit_release:
release_region(base, 3);
return err;
}
static void __exit i2c_parport_exit(void)
{
platform_driver_unregister(&i2c_parport_driver);
platform_device_unregister(pdev);
release_region(base, 3);
}
MODULE_AUTHOR("Jean Delvare <jdelvare@suse.de>");
MODULE_DESCRIPTION("I2C bus over parallel port (light)");
MODULE_LICENSE("GPL");
module_init(i2c_parport_init);
module_exit(i2c_parport_exit);