From 146c863ab9cb8a5b023a5bc1ca5ffa7834b14deb Mon Sep 17 00:00:00 2001 From: Michael Krufky Date: Mon, 5 Mar 2007 16:23:19 -0500 Subject: m920x: i2c cleanups From: Aapo Tahkola - Implement m920x i2c as suggested by Pierre Willenbrock - remove "magic" hack - r/w bit is not part of the i2c address - move hardware remarks to header file CC: Pierre Willenbrock Signed-off-by: Aapo Tahkola Signed-off-by: Michael Krufky --- linux/drivers/media/dvb/dvb-usb/m920x.h | 32 +++++++++++++++++++++++++------- 1 file changed, 25 insertions(+), 7 deletions(-) (limited to 'linux/drivers/media/dvb/dvb-usb/m920x.h') diff --git a/linux/drivers/media/dvb/dvb-usb/m920x.h b/linux/drivers/media/dvb/dvb-usb/m920x.h index c354196ff..c5ef592cb 100644 --- a/linux/drivers/media/dvb/dvb-usb/m920x.h +++ b/linux/drivers/media/dvb/dvb-usb/m920x.h @@ -19,17 +19,35 @@ #define M9206_MAX_FILTERS 8 -#define M9206_I2C_TUNER 0 -#define M9206_I2C_DEMOD 1 -#define M9206_I2C_MAX 2 +/* +sequences found in logs: +[index value] +0x80 write addr +(0x00 out byte)* +0x40 out byte + +0x80 write addr +(0x00 out byte)* +0x80 read addr +(0x21 in byte)* +0x60 in byte + +this sequence works: +0x80 read addr +(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 + */ struct m9206_state { u16 filters[M9206_MAX_FILTERS]; int filtering_enabled; int rep_count; - struct { - unsigned char addr; - unsigned char magic; - }i2c_r[M9206_I2C_MAX]; }; #endif -- cgit v1.2.3 From 2182011a1e9d29322026654f1f01cef05b907931 Mon Sep 17 00:00:00 2001 From: Trent Piepho Date: Mon, 5 Mar 2007 18:55:00 -0800 Subject: m920x: Improve I2C operations From: Trent Piepho Write some better documentation about what might be known about how the m920x I2C works, since a datasheet is lacking. The I2C xfer function should now handle more types of I2C transactions than it could before. Those it can't, will return error codes instead of being executed incorrectly. Multi-byte reads were not being done correctly, which should be fixed. Signed-off-by: Trent Piepho --- linux/drivers/media/dvb/dvb-usb/m920x.h | 28 +++++++++++++++++++++------- 1 file changed, 21 insertions(+), 7 deletions(-) (limited to 'linux/drivers/media/dvb/dvb-usb/m920x.h') diff --git a/linux/drivers/media/dvb/dvb-usb/m920x.h b/linux/drivers/media/dvb/dvb-usb/m920x.h index c5ef592cb..7dd3db65c 100644 --- a/linux/drivers/media/dvb/dvb-usb/m920x.h +++ b/linux/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]; -- cgit v1.2.3