diff options
Diffstat (limited to 'drivers/media/dvb/dvb-usb/m920x.h')
| -rw-r--r-- | drivers/media/dvb/dvb-usb/m920x.h | 28 |
1 files changed, 21 insertions, 7 deletions
diff --git a/drivers/media/dvb/dvb-usb/m920x.h b/drivers/media/dvb/dvb-usb/m920x.h index c5ef592..7dd3db6 100644 --- a/drivers/media/dvb/dvb-usb/m920x.h +++ b/drivers/media/dvb/dvb-usb/m920x.h @@ -37,13 +37,27 @@ this sequence works: (0x21 in byte)* 0x60 in byte -_my guess_: -0x80: begin i2c transfer using address. value=address<<1|(reading?1:0) -0x00: write byte -0x21: read byte, more to follow -0x40: write last byte of message sequence -0x60: read last byte of message sequence - */ +Guess at API of the I2C function: +I2C operation is done one byte at a time with USB control messages. The +index the messages is sent to is made up of a set of flags that control +the I2C bus state: +0x80: Send START condition. After a START condition, one would normally + always send the 7-bit slave I2C address as the 7 MSB, followed by + the read/write bit as the LSB. +0x40: Send STOP condition. This should be set on the last byte of an + I2C transaction. +0x20: Read a byte from the slave. As opposed to writing a byte to the + slave. The slave will normally not produce any data unless you + set the R/W bit to 1 when sending the slave's address after the + START condition. +0x01: Respond with ACK, as opposed to a NACK. For a multi-byte read, + the master should send an ACK, that is pull SDA low during the 9th + clock cycle, after every byte but the last. This flags only makes + sense when bit 0x20 is set, indicating a read. + +What any other bits might mean, or how to get the slave's ACK/NACK +response to a write, is unknown. +*/ struct m9206_state { u16 filters[M9206_MAX_FILTERS]; |