[RFC] ipmi: ipmi_ssif: require minimum response length

[Jian Zhang]

A valid IPMI over SSIF response must contain at least three bytes
(NetFn/LUN, Command and Completion Code).

Some DMA-only I2C controllers may return short reads instead of a
proper NACK when the response is not ready. Treat such short reads
as incomplete and retry until a full response is received.

Signed-off-by: Jian Zhang <zhangjian.3032@xxxxxxxxxxxxx>
---
 drivers/char/ipmi/ipmi_ssif.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/char/ipmi/ipmi_ssif.c b/drivers/char/ipmi/ipmi_ssif.c
index 37a5cb5c53f1..64ee939a7a4b 100644
--- a/drivers/char/ipmi/ipmi_ssif.c
+++ b/drivers/char/ipmi/ipmi_ssif.c
@@ -1300,7 +1300,7 @@ static int read_response(struct i2c_client *client, unsigned char *resp)
 	while (retry_cnt > 0) {
 		ret = i2c_smbus_read_block_data(client, SSIF_IPMI_RESPONSE,
 						resp);
-		if (ret > 0)
+		if (ret >= 3)
 			break;
 		msleep(SSIF_MSG_MSEC);
 		retry_cnt--;
-- 
2.20.1