[RFC 3/5] i2c: import SMBus stuff from linux
Antony Pavlov
antonynpavlov at gmail.com
Thu Jul 10 01:33:17 PDT 2014
Signed-off-by: Antony Pavlov <antonynpavlov at gmail.com>
---
drivers/i2c/i2c.c | 368 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
include/i2c/i2c.h | 64 ++++++++++
2 files changed, 432 insertions(+)
diff --git a/drivers/i2c/i2c.c b/drivers/i2c/i2c.c
index 9873957..167a5e4 100644
--- a/drivers/i2c/i2c.c
+++ b/drivers/i2c/i2c.c
@@ -159,6 +159,374 @@ int i2c_master_recv(struct i2c_client *client, char *buf, int count)
}
EXPORT_SYMBOL(i2c_master_recv);
+/* The SMBus parts */
+
+#define POLY (0x1070U << 3)
+static u8 crc8(u16 data)
+{
+ int i;
+
+ for (i = 0; i < 8; i++) {
+ if (data & 0x8000)
+ data = data ^ POLY;
+ data = data << 1;
+ }
+ return (u8)(data >> 8);
+}
+
+/* Incremental CRC8 over count bytes in the array pointed to by p */
+static u8 i2c_smbus_pec(u8 crc, u8 *p, size_t count)
+{
+ int i;
+
+ for (i = 0; i < count; i++)
+ crc = crc8((crc ^ p[i]) << 8);
+ return crc;
+}
+
+/* Assume a 7-bit address, which is reasonable for SMBus */
+static u8 i2c_smbus_msg_pec(u8 pec, struct i2c_msg *msg)
+{
+ /* The address will be sent first */
+ u8 addr = (msg->addr << 1) | !!(msg->flags & I2C_M_RD);
+ pec = i2c_smbus_pec(pec, &addr, 1);
+
+ /* The data buffer follows */
+ return i2c_smbus_pec(pec, msg->buf, msg->len);
+}
+
+/* Used for write only transactions */
+static inline void i2c_smbus_add_pec(struct i2c_msg *msg)
+{
+ msg->buf[msg->len] = i2c_smbus_msg_pec(0, msg);
+ msg->len++;
+}
+
+/* Return <0 on CRC error
+ If there was a write before this read (most cases) we need to take the
+ partial CRC from the write part into account.
+ Note that this function does modify the message (we need to decrease the
+ message length to hide the CRC byte from the caller). */
+static int i2c_smbus_check_pec(u8 cpec, struct i2c_msg *msg)
+{
+ u8 rpec = msg->buf[--msg->len];
+ cpec = i2c_smbus_msg_pec(cpec, msg);
+
+ if (rpec != cpec) {
+ pr_debug("i2c-core: Bad PEC 0x%02x vs. 0x%02x\n",
+ rpec, cpec);
+ return -EBADMSG;
+ }
+ return 0;
+}
+
+/**
+ * i2c_smbus_read_byte - SMBus "receive byte" protocol
+ * @client: Handle to slave device
+ *
+ * This executes the SMBus "receive byte" protocol, returning negative errno
+ * else the byte received from the device.
+ */
+s32 i2c_smbus_read_byte(const struct i2c_client *client)
+{
+ union i2c_smbus_data data;
+ int status;
+
+ status = i2c_smbus_xfer(client->adapter, client->addr, 0 /* client->flags */,
+ I2C_SMBUS_READ, 0,
+ I2C_SMBUS_BYTE, &data);
+ return (status < 0) ? status : data.byte;
+}
+EXPORT_SYMBOL(i2c_smbus_read_byte);
+
+/**
+ * i2c_smbus_write_byte - SMBus "send byte" protocol
+ * @client: Handle to slave device
+ * @value: Byte to be sent
+ *
+ * This executes the SMBus "send byte" protocol, returning negative errno
+ * else zero on success.
+ */
+s32 i2c_smbus_write_byte(const struct i2c_client *client, u8 value)
+{
+ return i2c_smbus_xfer(client->adapter, client->addr, 0 /* client->flags */,
+ I2C_SMBUS_WRITE, value, I2C_SMBUS_BYTE, NULL);
+}
+EXPORT_SYMBOL(i2c_smbus_write_byte);
+
+/**
+ * i2c_smbus_read_byte_data - SMBus "read byte" protocol
+ * @client: Handle to slave device
+ * @command: Byte interpreted by slave
+ *
+ * This executes the SMBus "read byte" protocol, returning negative errno
+ * else a data byte received from the device.
+ */
+s32 i2c_smbus_read_byte_data(const struct i2c_client *client, u8 command)
+{
+ union i2c_smbus_data data;
+ int status;
+
+ status = i2c_smbus_xfer(client->adapter, client->addr, 0 /* client->flags */,
+ I2C_SMBUS_READ, command,
+ I2C_SMBUS_BYTE_DATA, &data);
+ return (status < 0) ? status : data.byte;
+}
+EXPORT_SYMBOL(i2c_smbus_read_byte_data);
+
+/**
+ * i2c_smbus_write_byte_data - SMBus "write byte" protocol
+ * @client: Handle to slave device
+ * @command: Byte interpreted by slave
+ * @value: Byte being written
+ *
+ * This executes the SMBus "write byte" protocol, returning negative errno
+ * else zero on success.
+ */
+s32 i2c_smbus_write_byte_data(const struct i2c_client *client, u8 command,
+ u8 value)
+{
+ union i2c_smbus_data data;
+ data.byte = value;
+ return i2c_smbus_xfer(client->adapter, client->addr, 0 /* client->flags */,
+ I2C_SMBUS_WRITE, command,
+ I2C_SMBUS_BYTE_DATA, &data);
+}
+EXPORT_SYMBOL(i2c_smbus_write_byte_data);
+
+/**
+ * i2c_smbus_read_word_data - SMBus "read word" protocol
+ * @client: Handle to slave device
+ * @command: Byte interpreted by slave
+ *
+ * This executes the SMBus "read word" protocol, returning negative errno
+ * else a 16-bit unsigned "word" received from the device.
+ */
+s32 i2c_smbus_read_word_data(const struct i2c_client *client, u8 command)
+{
+ union i2c_smbus_data data;
+ int status;
+
+ status = i2c_smbus_xfer(client->adapter, client->addr, 0 /* client->flags */,
+ I2C_SMBUS_READ, command,
+ I2C_SMBUS_WORD_DATA, &data);
+ return (status < 0) ? status : data.word;
+}
+EXPORT_SYMBOL(i2c_smbus_read_word_data);
+
+/**
+ * i2c_smbus_write_word_data - SMBus "write word" protocol
+ * @client: Handle to slave device
+ * @command: Byte interpreted by slave
+ * @value: 16-bit "word" being written
+ *
+ * This executes the SMBus "write word" protocol, returning negative errno
+ * else zero on success.
+ */
+s32 i2c_smbus_write_word_data(const struct i2c_client *client, u8 command,
+ u16 value)
+{
+ union i2c_smbus_data data;
+ data.word = value;
+ return i2c_smbus_xfer(client->adapter, client->addr, 0 /* client->flags */,
+ I2C_SMBUS_WRITE, command,
+ I2C_SMBUS_WORD_DATA, &data);
+}
+EXPORT_SYMBOL(i2c_smbus_write_word_data);
+
+/* Returns the number of read bytes */
+s32 i2c_smbus_read_i2c_block_data(const struct i2c_client *client, u8 command,
+ u8 length, u8 *values)
+{
+ union i2c_smbus_data data;
+ int status;
+
+ if (length > I2C_SMBUS_BLOCK_MAX)
+ length = I2C_SMBUS_BLOCK_MAX;
+ data.block[0] = length;
+ status = i2c_smbus_xfer(client->adapter, client->addr, 0 /* client->flags */,
+ I2C_SMBUS_READ, command,
+ I2C_SMBUS_I2C_BLOCK_DATA, &data);
+ if (status < 0)
+ return status;
+
+ memcpy(values, &data.block[1], data.block[0]);
+ return data.block[0];
+}
+EXPORT_SYMBOL(i2c_smbus_read_i2c_block_data);
+
+s32 i2c_smbus_write_i2c_block_data(const struct i2c_client *client, u8 command,
+ u8 length, const u8 *values)
+{
+ union i2c_smbus_data data;
+
+ if (length > I2C_SMBUS_BLOCK_MAX)
+ length = I2C_SMBUS_BLOCK_MAX;
+ data.block[0] = length;
+ memcpy(data.block + 1, values, length);
+ return i2c_smbus_xfer(client->adapter, client->addr, 0 /* client->flags */,
+ I2C_SMBUS_WRITE, command,
+ I2C_SMBUS_I2C_BLOCK_DATA, &data);
+}
+EXPORT_SYMBOL(i2c_smbus_write_i2c_block_data);
+
+/* Simulate a SMBus command using the i2c protocol
+ No checking of parameters is done! */
+static s32 i2c_smbus_xfer_emulated(struct i2c_adapter *adapter, u16 addr,
+ unsigned short flags,
+ char read_write, u8 command, int size,
+ union i2c_smbus_data *data)
+{
+ /* So we need to generate a series of msgs. In the case of writing, we
+ need to use only one message; when reading, we need two. We initialize
+ most things with sane defaults, to keep the code below somewhat
+ simpler. */
+ unsigned char msgbuf0[I2C_SMBUS_BLOCK_MAX+3];
+ unsigned char msgbuf1[I2C_SMBUS_BLOCK_MAX+2];
+ int num = read_write == I2C_SMBUS_READ ? 2 : 1;
+ int i;
+ u8 partial_pec = 0;
+ int status;
+ struct i2c_msg msg[2] = {
+ {
+ .addr = addr,
+ .flags = flags,
+ .len = 1,
+ .buf = msgbuf0,
+ }, {
+ .addr = addr,
+ .flags = flags | I2C_M_RD,
+ .len = 0,
+ .buf = msgbuf1,
+ },
+ };
+
+ msgbuf0[0] = command;
+ switch (size) {
+ case I2C_SMBUS_QUICK:
+ msg[0].len = 0;
+ /* Special case: The read/write field is used as data */
+ msg[0].flags = flags | (read_write == I2C_SMBUS_READ ?
+ I2C_M_RD : 0);
+ num = 1;
+ break;
+ case I2C_SMBUS_BYTE:
+ if (read_write == I2C_SMBUS_READ) {
+ /* Special case: only a read! */
+ msg[0].flags = I2C_M_RD | flags;
+ num = 1;
+ }
+ break;
+ case I2C_SMBUS_BYTE_DATA:
+ if (read_write == I2C_SMBUS_READ)
+ msg[1].len = 1;
+ else {
+ msg[0].len = 2;
+ msgbuf0[1] = data->byte;
+ }
+ break;
+ case I2C_SMBUS_WORD_DATA:
+ if (read_write == I2C_SMBUS_READ)
+ msg[1].len = 2;
+ else {
+ msg[0].len = 3;
+ msgbuf0[1] = data->word & 0xff;
+ msgbuf0[2] = data->word >> 8;
+ }
+ break;
+ case I2C_SMBUS_I2C_BLOCK_DATA:
+ if (read_write == I2C_SMBUS_READ) {
+ msg[1].len = data->block[0];
+ } else {
+ msg[0].len = data->block[0] + 1;
+ if (msg[0].len > I2C_SMBUS_BLOCK_MAX + 1) {
+ dev_err(&adapter->dev,
+ "Invalid block write size %d\n",
+ data->block[0]);
+ return -EINVAL;
+ }
+ for (i = 1; i <= data->block[0]; i++)
+ msgbuf0[i] = data->block[i];
+ }
+ break;
+ default:
+ dev_err(&adapter->dev, "Unsupported transaction %d\n", size);
+ return -EOPNOTSUPP;
+ }
+
+ i = ((flags & I2C_CLIENT_PEC) && size != I2C_SMBUS_QUICK
+ && size != I2C_SMBUS_I2C_BLOCK_DATA);
+ if (i) {
+ /* Compute PEC if first message is a write */
+ if (!(msg[0].flags & I2C_M_RD)) {
+ if (num == 1) /* Write only */
+ i2c_smbus_add_pec(&msg[0]);
+ else /* Write followed by read */
+ partial_pec = i2c_smbus_msg_pec(0, &msg[0]);
+ }
+ /* Ask for PEC if last message is a read */
+ if (msg[num-1].flags & I2C_M_RD)
+ msg[num-1].len++;
+ }
+
+ status = i2c_transfer(adapter, msg, num);
+ if (status < 0)
+ return status;
+
+ /* Check PEC if last message is a read */
+ if (i && (msg[num-1].flags & I2C_M_RD)) {
+ status = i2c_smbus_check_pec(partial_pec, &msg[num-1]);
+ if (status < 0)
+ return status;
+ }
+
+ if (read_write == I2C_SMBUS_READ)
+ switch (size) {
+ case I2C_SMBUS_BYTE:
+ data->byte = msgbuf0[0];
+ break;
+ case I2C_SMBUS_BYTE_DATA:
+ data->byte = msgbuf1[0];
+ break;
+ case I2C_SMBUS_WORD_DATA:
+ data->word = msgbuf1[0] | (msgbuf1[1] << 8);
+ break;
+ case I2C_SMBUS_I2C_BLOCK_DATA:
+ for (i = 0; i < data->block[0]; i++)
+ data->block[i+1] = msgbuf1[i];
+ break;
+ }
+ return 0;
+}
+
+/**
+ * i2c_smbus_xfer - execute SMBus protocol operations
+ * @adapter: Handle to I2C bus
+ * @addr: Address of SMBus slave on that bus
+ * @flags: I2C_CLIENT_* flags (usually zero or I2C_CLIENT_PEC)
+ * @read_write: I2C_SMBUS_READ or I2C_SMBUS_WRITE
+ * @command: Byte interpreted by slave, for protocols which use such bytes
+ * @protocol: SMBus protocol operation to execute, such as I2C_SMBUS_PROC_CALL
+ * @data: Data to be read or written
+ *
+ * This executes an SMBus protocol operation, and returns a negative
+ * errno code else zero on success.
+ */
+s32 i2c_smbus_xfer(struct i2c_adapter *adapter, u16 addr, unsigned short flags,
+ char read_write, u8 command, int protocol,
+ union i2c_smbus_data *data)
+{
+ s32 res;
+
+ flags &= I2C_M_TEN | I2C_CLIENT_PEC | I2C_CLIENT_SCCB;
+
+ res = i2c_smbus_xfer_emulated(adapter, addr, flags, read_write,
+ command, protocol, data);
+
+ return res;
+}
+EXPORT_SYMBOL(i2c_smbus_xfer);
+
int i2c_read_reg(struct i2c_client *client, u32 addr, u8 *buf, u16 count)
{
u8 msgbuf[2];
diff --git a/include/i2c/i2c.h b/include/i2c/i2c.h
index a107f5e..43038ec 100644
--- a/include/i2c/i2c.h
+++ b/include/i2c/i2c.h
@@ -85,6 +85,70 @@ struct i2c_client {
#define to_i2c_client(a) container_of(a, struct i2c_client, dev)
+/*flags for the client struct: */
+#define I2C_CLIENT_PEC 0x04 /* Use Packet Error Checking */
+#define I2C_CLIENT_TEN 0x10 /* we have a ten bit chip address */
+ /* Must equal I2C_M_TEN below */
+#define I2C_CLIENT_WAKE 0x80 /* for board_info; true iff can wake */
+#define I2C_CLIENT_SCCB 0x9000 /* Use Omnivision SCCB protocol */
+ /* Must match I2C_M_STOP|IGNORE_NAK */
+
+/*
+ * Data for SMBus Messages
+ */
+#define I2C_SMBUS_BLOCK_MAX 32 /* As specified in SMBus standard */
+union i2c_smbus_data {
+ __u8 byte;
+ __u16 word;
+ __u8 block[I2C_SMBUS_BLOCK_MAX + 2]; /* block[0] is used for length */
+ /* and one more for user-space compatibility */
+};
+
+/* i2c_smbus_xfer read or write markers */
+#define I2C_SMBUS_READ 1
+#define I2C_SMBUS_WRITE 0
+
+/* SMBus transaction types (size parameter in the above functions)
+ Note: these no longer correspond to the (arbitrary) PIIX4 internal codes! */
+#define I2C_SMBUS_QUICK 0
+#define I2C_SMBUS_BYTE 1
+#define I2C_SMBUS_BYTE_DATA 2
+#define I2C_SMBUS_WORD_DATA 3
+#define I2C_SMBUS_PROC_CALL 4
+#define I2C_SMBUS_BLOCK_DATA 5
+#define I2C_SMBUS_I2C_BLOCK_BROKEN 6
+#define I2C_SMBUS_BLOCK_PROC_CALL 7 /* SMBus 2.0 */
+#define I2C_SMBUS_I2C_BLOCK_DATA 8
+
+/* This is the very generalized SMBus access routine. You probably do not
+ want to use this, though; one of the functions below may be much easier,
+ and probably just as fast.
+ Note that we use i2c_adapter here, because you do not need a specific
+ smbus adapter to call this function. */
+extern s32 i2c_smbus_xfer(struct i2c_adapter *adapter, u16 addr,
+ unsigned short flags, char read_write, u8 command,
+ int size, union i2c_smbus_data *data);
+
+/* Now follow the 'nice' access routines. These also document the calling
+ conventions of i2c_smbus_xfer. */
+
+extern s32 i2c_smbus_read_byte(const struct i2c_client *client);
+extern s32 i2c_smbus_write_byte(const struct i2c_client *client, u8 value);
+extern s32 i2c_smbus_read_byte_data(const struct i2c_client *client,
+ u8 command);
+extern s32 i2c_smbus_write_byte_data(const struct i2c_client *client,
+ u8 command, u8 value);
+extern s32 i2c_smbus_read_word_data(const struct i2c_client *client,
+ u8 command);
+extern s32 i2c_smbus_write_word_data(const struct i2c_client *client,
+ u8 command, u16 value);
+
+/* Returns the number of read bytes */
+extern s32 i2c_smbus_read_i2c_block_data(const struct i2c_client *client,
+ u8 command, u8 length, u8 *values);
+extern s32 i2c_smbus_write_i2c_block_data(const struct i2c_client *client,
+ u8 command, u8 length,
+ const u8 *values);
/**
* struct i2c_board_info - template for device creation
--
2.0.1
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