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V4L/DVB (5428): M920x: Detect zero-length I2C messages and fix a typo 

Change a 00 to just 0
Detect zero-length I2C messages and return not supported.  I think I know
how to send one, but the problem is getting the slave's ack.  The only
point of a zero-length message is for probing; too see if the slave will
ack its address.  Since we don't know how to get the ack, we can't
support zero-length messages in a useful way, so it's probably best to
just return not supported for them.

Signed-off-by: Trent Piepho <xyzzy@speakeasy.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>
This commit is contained in:
Trent Piepho 2007-03-12 12:13:12 -03:00 committed by Mauro Carvalho Chehab
parent d40860f8e2
commit 57f8dcf90b
1 changed files with 7 additions and 2 deletions
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9
drivers/media/dvb/dvb-usb/m920x.c
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@ -148,13 +148,18 @@ static int m9206_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msg[],
return -EAGAIN;
for (i = 0; i < num; i++) {
if (msg[i].flags & (I2C_M_NO_RD_ACK|I2C_M_IGNORE_NAK|I2C_M_TEN)) {
if (msg[i].flags & (I2C_M_NO_RD_ACK|I2C_M_IGNORE_NAK|I2C_M_TEN) ||
msg[i].len == 0) {
/* For a 0 byte message, I think sending the address to index 0x80|0x40
* would be the correct thing to do. However, zero byte messages are
* only used for probing, and since we don't know how to get the slave's
* ack, we can't probe. */
ret = -ENOTSUPP;
goto unlock;
}
/* Send START & address/RW bit */
if (!(msg[i].flags & I2C_M_NOSTART)) {
if ((ret = m9206_write(d->udev, M9206_I2C, (msg[i].addr<<1)|(msg[i].flags&I2C_M_RD?0x01:00), 0x80)) != 0)
if ((ret = m9206_write(d->udev, M9206_I2C, (msg[i].addr<<1)|(msg[i].flags&I2C_M_RD?0x01:0), 0x80)) != 0)
goto unlock;
/* Should check for ack here, if we knew how. */
}