the i2c-tools package.
I2C device files are character device files with major device number 89
-and a minor device number corresponding to the number assigned as
-explained above. They should be called "i2c-%d" (i2c-0, i2c-1, ...,
+and a minor device number corresponding to the number assigned as
+explained above. They should be called "i2c-%d" (i2c-0, i2c-1, ...,
i2c-10, ...). All 256 minor device numbers are reserved for i2c.
#include <linux/i2c-dev.h>
#include <i2c/smbus.h>
-(Please note that there are two files named "i2c-dev.h" out there. One is
-distributed with the Linux kernel and the other one is included in the
-source tree of i2c-tools. They used to be different in content but since 2012
-they're identical. You should use "linux/i2c-dev.h").
-
Now, you have to decide which adapter you want to access. You should
inspect /sys/class/i2c-dev/ or run "i2cdetect -l" to decide this.
Adapter numbers are assigned somewhat dynamically, so you can not
int file;
int adapter_nr = 2; /* probably dynamically determined */
char filename[20];
-
+
snprintf(filename, 19, "/dev/i2c-%d", adapter_nr);
file = open(filename, O_RDWR);
if (file < 0) {
/* res contains the read word */
}
- /* Using I2C Write, equivalent of
- i2c_smbus_write_word_data(file, reg, 0x6543) */
+ /*
+ * Using I2C Write, equivalent of
+ * i2c_smbus_write_word_data(file, reg, 0x6543)
+ */
buf[0] = reg;
buf[1] = 0x43;
buf[2] = 0x65;
set in each message, overriding the values set with the above ioctl's.
ioctl(file, I2C_SMBUS, struct i2c_smbus_ioctl_data *args)
- Not meant to be called directly; instead, use the access functions
- below.
+ If possible, use the provided i2c_smbus_* methods described below instead
+ of issuing direct ioctls.
You can do plain i2c transactions by using read(2) and write(2) calls.
You do not need to pass the address byte; instead, set it through
ioctl I2C_SLAVE before you try to access the device.
-You can do SMBus level transactions (see documentation file smbus-protocol
+You can do SMBus level transactions (see documentation file smbus-protocol
for details) through the following functions:
__s32 i2c_smbus_write_quick(int file, __u8 value);
__s32 i2c_smbus_read_byte(int file);
__s32 i2c_smbus_write_word_data(int file, __u8 command, __u16 value);
__s32 i2c_smbus_process_call(int file, __u8 command, __u16 value);
__s32 i2c_smbus_read_block_data(int file, __u8 command, __u8 *values);
- __s32 i2c_smbus_write_block_data(int file, __u8 command, __u8 length,
+ __s32 i2c_smbus_write_block_data(int file, __u8 command, __u8 length,
__u8 *values);
All these transactions return -1 on failure; you can read errno to see
what happened. The 'write' transactions return 0 on success; the
returns the number of values read. The block buffers need not be longer
than 32 bytes.
-The above functions are all inline functions, that resolve to calls to
-the i2c_smbus_access function, that on its turn calls a specific ioctl
-with the data in a specific format. Read the source code if you
-want to know what happens behind the screens.
+The above functions are made available by linking against the libi2c library,
+which is provided by the i2c-tools project. See:
+https://git.kernel.org/pub/scm/utils/i2c-tools/i2c-tools.git/.
Implementation details
u32 count;
int irq;
int err;
+ bool is_suspended;
};
static void sprd_i2c_set_count(struct sprd_i2c *i2c_dev, u32 count)
struct sprd_i2c *i2c_dev = i2c_adap->algo_data;
int im, ret;
+ if (i2c_dev->is_suspended)
+ return -EBUSY;
+
ret = pm_runtime_get_sync(i2c_dev->dev);
if (ret < 0)
return ret;
struct sprd_i2c *i2c_dev = dev_id;
struct i2c_msg *msg = i2c_dev->msg;
bool ack = !(readl(i2c_dev->base + I2C_STATUS) & I2C_RX_ACK);
- u32 i2c_count = readl(i2c_dev->base + I2C_COUNT);
u32 i2c_tran;
if (msg->flags & I2C_M_RD)
i2c_tran = i2c_dev->count >= I2C_FIFO_FULL_THLD;
else
- i2c_tran = i2c_count;
+ i2c_tran = i2c_dev->count;
/*
* If we got one ACK from slave when writing data, and we did not
{
struct sprd_i2c *i2c_dev = dev_id;
struct i2c_msg *msg = i2c_dev->msg;
- u32 i2c_count = readl(i2c_dev->base + I2C_COUNT);
bool ack = !(readl(i2c_dev->base + I2C_STATUS) & I2C_RX_ACK);
u32 i2c_tran;
if (msg->flags & I2C_M_RD)
i2c_tran = i2c_dev->count >= I2C_FIFO_FULL_THLD;
else
- i2c_tran = i2c_count;
+ i2c_tran = i2c_dev->count;
/*
* If we did not get one ACK from slave when writing data, then we
static int __maybe_unused sprd_i2c_suspend_noirq(struct device *pdev)
{
+ struct sprd_i2c *i2c_dev = dev_get_drvdata(pdev);
+
+ i2c_lock_adapter(&i2c_dev->adap);
+ i2c_dev->is_suspended = true;
+ i2c_unlock_adapter(&i2c_dev->adap);
+
return pm_runtime_force_suspend(pdev);
}
static int __maybe_unused sprd_i2c_resume_noirq(struct device *pdev)
{
+ struct sprd_i2c *i2c_dev = dev_get_drvdata(pdev);
+
+ i2c_lock_adapter(&i2c_dev->adap);
+ i2c_dev->is_suspended = false;
+ i2c_unlock_adapter(&i2c_dev->adap);
+
return pm_runtime_force_resume(pdev);
}
projects / linux-2.6-block.git / commitdiff