diff options
| -rw-r--r-- | drivers/hid/hid-ft260.c | 17 |
1 files changed, 12 insertions, 5 deletions
diff --git a/drivers/hid/hid-ft260.c b/drivers/hid/hid-ft260.c index a354089bb747..91f9087e49dc 100644 --- a/drivers/hid/hid-ft260.c +++ b/drivers/hid/hid-ft260.c @@ -30,12 +30,19 @@ MODULE_PARM_DESC(debug, "Toggle FT260 debugging messages"); #define FT260_REPORT_MAX_LENGTH (64) #define FT260_I2C_DATA_REPORT_ID(len) (FT260_I2C_REPORT_MIN + (len - 1) / 4) + /* - * The input report format assigns 62 bytes for the data payload, but ft260 - * returns 60 and 2 in two separate transactions. To minimize transfer time - * in reading chunks mode, set the maximum read payload length to 60 bytes. - */ -#define FT260_RD_DATA_MAX (60) + * The ft260 input report format defines 62 bytes for the data payload, but + * when requested 62 bytes, the controller returns 60 and 2 in separate input + * reports. To achieve better performance with the multi-report read data + * transfers, we set the maximum read payload length to a multiple of 60. + * With a 100 kHz I2C clock, one 240 bytes read takes about 1/27 second, + * which is excessive; On the other hand, some higher layer drivers like at24 + * or optoe limit the i2c reads to 128 bytes. To not block other drivers out + * of I2C for potentially troublesome amounts of time, we select the maximum + * read payload length to be 180 bytes. +*/ +#define FT260_RD_DATA_MAX (180) #define FT260_WR_DATA_MAX (60) /* |