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authorJean Delvare <khali@linux-fr.org>2010-03-02 12:23:40 +0100
committerJean Delvare <khali@linux-fr.org>2010-03-02 12:23:40 +0100
commitc05d490234b7cf1715d9568d2041d9bc598a0b45 (patch)
parent393764340beb595c1ad7dd2d2243c2b6551aaa71 (diff)
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>
1 files changed, 5 insertions, 3 deletions
diff --git a/drivers/i2c/busses/i2c-tiny-usb.c b/drivers/i2c/busses/i2c-tiny-usb.c
index 41adb390e49c..b5b1bbf37d3c 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);

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