From c05d490234b7cf1715d9568d2041d9bc598a0b45 Mon Sep 17 00:00:00 2001 From: Jean Delvare <khali@linux-fr.org> Date: Tue, 2 Mar 2010 12:23:40 +0100 Subject: [PATCH] i2c-tiny-usb: Fix a comment on bus frequency 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> --- drivers/i2c/busses/i2c-tiny-usb.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/drivers/i2c/busses/i2c-tiny-usb.c b/drivers/i2c/busses/i2c-tiny-usb.c index 41adb390e49cf8..b5b1bbf37d3c5b 100644 --- a/drivers/i2c/busses/i2c-tiny-usb.c +++ b/drivers/i2c/busses/i2c-tiny-usb.c @@ -31,11 +31,13 @@ #define CMD_I2C_IO_BEGIN (1<<0) #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; module_param(delay, ushort, 0); -MODULE_PARM_DESC(delay, "bit delay in microseconds, " - "e.g. 10 for 100kHz (default is 100kHz)"); +MODULE_PARM_DESC(delay, "bit delay in microseconds " + "(default is 10us for 100kHz max)"); static int usb_read(struct i2c_adapter *adapter, int cmd, int value, int index, void *data, int len); -- GitLab