On Friday 28 November 2008, hvaibhav@xxxxxx wrote:
> +static int tvp514x_read_reg(struct i2c_client *client, u8 reg, u8 *val)
> +{
> + int err;
> + struct i2c_msg msg[2];
> + u8 data;
> +
> + if (!client->adapter)
> + return -ENODEV;
> +
> + /* [MSG1] fill the register address data */
> + data = reg;
> + msg[0].addr = client->addr;
> + msg[0].len = 1;
> + msg[0].flags = 0;
> + msg[0].buf = &data;
> +
> + /* [MSG2] fill the data rx buffer */
> + msg[1].addr = client->addr;
> + msg[1].len = 1; /* only 1 byte */
> + msg[1].flags = I2C_M_RD; /* Read the register values */
> + msg[1].buf = val;
> + err = i2c_transfer(client->adapter, msg, 2);
Better:
err = i2c_smbus_read_byte_data(client, reg);
if (err >= 0) {
*val = err;
err = 0;
}
return err;
Though maybe the calling convention should be simplified,
And of course, probe() should verify that the adapter can
support the SMBus byte_data operations.
> + if (err >= 0)
> + return 0;
> +
> + v4l_dbg(1, debug, client,
> + "read from device 0x%.2x, offset 0x%.2x error %d\n",
> + client->addr, reg, err);
> +
> + return err;
> +}
> +
> +/*
> + * Write a value to a register in an TVP5146/47 decoder device.
> + * Returns zero if successful, or non-zero otherwise.
> + */
> +static int tvp514x_write_reg(struct i2c_client *client, u8 reg, u8 val)
> +{
> + int err;
> + int retry = 0;
> + struct i2c_msg msg[1];
> + u8 data[2];
> +
> + if (!client->adapter)
> + return -ENODEV;
> +
> +again:
> + data[0] = reg; /* Register offset */
> + data[1] = val; /* Register value */
> + msg->addr = client->addr;
> + msg->len = 2;
> + msg->flags = 0; /* write operation */
> + msg->buf = data;
> +
> + err = i2c_transfer(client->adapter, msg, 1);
> + if (err >= 0)
> + return 0;
Likewise:
again:
err = i2c_smbus_write_byte_data(client, reg, val);
if (err == 0)
return 0;
/* else retry */
By the way, while I applaud actually *having* fault handling in
I2C driver code -- faults can happen, and pathetically few Linux
drivers tolerate them from I2C -- I'm curious why only the write
path handles them, not the read path.
> +
> + v4l_dbg(1, debug, client,
> + "wrote 0x%.2x to offset 0x%.2x error %d\n", val, reg, err);
> + if (retry <= I2C_RETRY_COUNT) {
> + v4l_warn(client, "retry ... %d\n", retry);
> + retry++;
> + schedule_timeout(msecs_to_jiffies(20));
> + goto again;
> + }
> + return err;
> +}
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