viafb: fix i2c_transfer error handling
i2c_transfer returns negative errno on error and number of messages
processed on success. Just returning this value would give a poor
interface as it is not obvious that you must compare with 2 after reading
1 or n bytes and with 1 after writing 1 byte to determine if it was
successful. To avoid this error prone interface convert the error code
of a successful read/write to zero and all other non-negative values to
an negative error code.
This fixes a regression introduced by
via: Rationalize vt1636 detection
which resulted in no longer detecting a VT1636 chip and therefore has
broken the output in configurations which contain this chip.
Signed-off-by: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>
Acked-by: Jonathan Corbet <corbet@lwn.net>
Cc: Joseph Chan <JosephChan@via.com.tw>
Cc: stable@kernel.org
diff --git a/drivers/video/via/via_i2c.c b/drivers/video/via/via_i2c.c
index da9e4ca..021112e 100644
--- a/drivers/video/via/via_i2c.c
+++ b/drivers/video/via/via_i2c.c
@@ -114,6 +114,7 @@
int viafb_i2c_readbyte(u8 adap, u8 slave_addr, u8 index, u8 *pdata)
{
+ int ret;
u8 mm1[] = {0x00};
struct i2c_msg msgs[2];
@@ -126,11 +127,18 @@
mm1[0] = index;
msgs[0].len = 1; msgs[1].len = 1;
msgs[0].buf = mm1; msgs[1].buf = pdata;
- return i2c_transfer(&via_i2c_par[adap].adapter, msgs, 2);
+ ret = i2c_transfer(&via_i2c_par[adap].adapter, msgs, 2);
+ if (ret == 2)
+ ret = 0;
+ else if (ret >= 0)
+ ret = -EIO;
+
+ return ret;
}
int viafb_i2c_writebyte(u8 adap, u8 slave_addr, u8 index, u8 data)
{
+ int ret;
u8 msg[2] = { index, data };
struct i2c_msg msgs;
@@ -140,11 +148,18 @@
msgs.addr = slave_addr / 2;
msgs.len = 2;
msgs.buf = msg;
- return i2c_transfer(&via_i2c_par[adap].adapter, &msgs, 1);
+ ret = i2c_transfer(&via_i2c_par[adap].adapter, &msgs, 1);
+ if (ret == 1)
+ ret = 0;
+ else if (ret >= 0)
+ ret = -EIO;
+
+ return ret;
}
int viafb_i2c_readbytes(u8 adap, u8 slave_addr, u8 index, u8 *buff, int buff_len)
{
+ int ret;
u8 mm1[] = {0x00};
struct i2c_msg msgs[2];
@@ -156,7 +171,13 @@
mm1[0] = index;
msgs[0].len = 1; msgs[1].len = buff_len;
msgs[0].buf = mm1; msgs[1].buf = buff;
- return i2c_transfer(&via_i2c_par[adap].adapter, msgs, 2);
+ ret = i2c_transfer(&via_i2c_par[adap].adapter, msgs, 2);
+ if (ret == 2)
+ ret = 0;
+ else if (ret >= 0)
+ ret = -EIO;
+
+ return ret;
}
/*