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i2c-tiny-usb: Fix a comment on bus frequency

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The description of the delay parameter is incomplete, it suggests that
there is a direct relation between the delay value and the bus
frequency. In fact, due to additional delays in the i2c bitbanging
code, the i2c clock is always much slower.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Cc: Till Harbaum <Till@Harbaum.org>
This commit is contained in:
Jean Delvare 2010-03-02 12:23:40 +01:00
parent 393764340b
commit c05d490234
1 changed files with 5 additions and 3 deletions
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8
drivers/i2c/busses/i2c-tiny-usb.c
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@ -31,11 +31,13 @@
#define CMD_I2C_IO_BEGIN (1<<0) #define CMD_I2C_IO_BEGIN (1<<0)
#define CMD_I2C_IO_END (1<<1) #define CMD_I2C_IO_END (1<<1)
/* i2c bit delay, default is 10us -> 100kHz */ /* i2c bit delay, default is 10us -> 100kHz max
(in practice, due to additional delays in the i2c bitbanging
code this results in a i2c clock of about 50kHz) */
static unsigned short delay = 10; static unsigned short delay = 10;
module_param(delay, ushort, 0); module_param(delay, ushort, 0);
MODULE_PARM_DESC(delay, "bit delay in microseconds, " MODULE_PARM_DESC(delay, "bit delay in microseconds "
"e.g. 10 for 100kHz (default is 100kHz)"); "(default is 10us for 100kHz max)");
static int usb_read(struct i2c_adapter *adapter, int cmd, static int usb_read(struct i2c_adapter *adapter, int cmd,
int value, int index, void *data, int len); int value, int index, void *data, int len);