V4L/DVB (5428): M920x: Detect zero-length I2C messages and fix a typo (57f8dcf9) · Commits · 戴 / test

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>

drivers/media/dvb/dvb-usb/m920x.c

+7 −2

Original line number	Diff line number	Diff line
		@@ -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. */
		}

Admin message