Linux I2C read/write instance

During this time, a capacitive touch screen was created. After experiment, we finally tried it out, because we didn't have this one in the past, and we have accumulated a lot of experience. There are two key points to illustrate:

(1) read/write functions of I2C devices. The sequence is as follows:

Based on the features, I did not use the SMBus read/write function, but I still use the I2C read/write function to handle it:

Static struct i2c_client * g_client; // client registered with the I2C Device

Static int gw8158_read_register_packet (u8 bufp [13]) // read 13 bytes and use Array
{
Int ret = 0, Count = 0;
U8 buffer [13];
Unsigned long flags;
Spinlock_t * Lock = get_i2c_lock (); // gets the I2C spin lock.
If (g_client = NULL) | (Lock = NULL ))
Return-1;

Spin_lock_irqsave (lock, flags); // spin lock for I2C operations
Ret = i2c_master_recv (g_client, buffer, 13); // The device address is written by default. Because there is no sub-address, you can directly receive
Spin_unlock_irqrestore (lock, flags );
If (Ret> 0)
{
For (COUNT = 0; count <13; count ++)
Bufp [count] = buffer [count]; // If read succeeds, return the register value
Printk ("gw8158_read_register_packet OK/N ");
}
Return ret;
}
Static int gw8158_write_register_byte (const u8 subaddress, u8 bufp)
{
Int ret;
U8 buffer [2];
Unsigned long flags;
Spinlock_t * Lock = get_i2c_lock ();
If (g_client = NULL) | (Lock = NULL ))
Return-1;

Buffer [0] = subaddress;
Buffer [1] = bufp;
Spin_lock_irqsave (lock, flags );
If (i2c_master_send (g_client, buffer, 1) <0) // write the subaddress once. This write only verifies whether the communication is successful. Because there is no data
Return-1; // It does not make sense if the write is successful. The real write control will not be affected.

Ret = i2c_master_send (g_client, buffer, 2); // write the subaddress and data only once.
Spin_unlock_irqrestore (lock, flags );
If (Ret> 0)
Printk ("gw8158_write_register_byte OK/N ");
Return ret;
}
(2) reset part.

It is a high reset, so there must be a sequence from low to high, but it cannot always be high, otherwise it will always reset, it has to be pulled down. As follows:

Pxa3xx_outgpio_set_level (mfp_ts_gw8158_rst, gpio_level_low );
Mdelay (30 );
Pxa3xx_outgpio_set_level (mfp_ts_gw8158_rst, gpio_level_high );
Mdelay (20 );
Pxa3xx_outgpio_set_level (mfp_ts_gw8158_rst, gpio_level_low );
Mdelay (1000 );