i2c: add quirk structure to describe adapter flaws

int i2c_generic_gpio_recovery(struct i2c_adapter *adap);

int i2c_generic_scl_recovery(struct i2c_adapter *adap);

/**

 * struct i2c_adapter_quirks - describe flaws of an i2c adapter

 * @flags: see I2C_AQ_* for possible flags and read below

 * @max_num_msgs: maximum number of messages per transfer

 * @max_write_len: maximum length of a write message

 * @max_read_len: maximum length of a read message

 * @max_comb_1st_msg_len: maximum length of the first msg in a combined message

 * @max_comb_2nd_msg_len: maximum length of the second msg in a combined message

 *

 * Note about combined messages: Some I2C controllers can only send one message

 * per transfer, plus something called combined message or write-then-read.

 * This is (usually) a small write message followed by a read message and

 * barely enough to access register based devices like EEPROMs. There is a flag

 * to support this mode. It implies max_num_msg = 2 and does the length checks

 * with max_comb_*_len because combined message mode usually has its own

 * limitations. Because of HW implementations, some controllers can actually do

 * write-then-anything or other variants. To support that, write-then-read has

 * been broken out into smaller bits like write-first and read-second which can

 * be combined as needed.

 */

struct i2c_adapter_quirks {

	u64 flags;

	int max_num_msgs;

	u16 max_write_len;

	u16 max_read_len;

	u16 max_comb_1st_msg_len;

	u16 max_comb_2nd_msg_len;

};

/* enforce max_num_msgs = 2 and use max_comb_*_len for length checks */

#define I2C_AQ_COMB			BIT(0)

/* first combined message must be write */

#define I2C_AQ_COMB_WRITE_FIRST		BIT(1)

/* second combined message must be read */

#define I2C_AQ_COMB_READ_SECOND		BIT(2)

/* both combined messages must have the same target address */

#define I2C_AQ_COMB_SAME_ADDR		BIT(3)

/* convenience macro for typical write-then read case */

#define I2C_AQ_COMB_WRITE_THEN_READ	(I2C_AQ_COMB | I2C_AQ_COMB_WRITE_FIRST | \

					 I2C_AQ_COMB_READ_SECOND | I2C_AQ_COMB_SAME_ADDR)

/*

 * i2c_adapter is the structure used to identify a physical i2c bus along

 * with the access algorithms necessary to access it.

	struct list_head userspace_clients;

	struct i2c_bus_recovery_info *bus_recovery_info;

	const struct i2c_adapter_quirks *quirks;

};

#define to_i2c_adapter(d) container_of(d, struct i2c_adapter, dev)