V4L/DVB (4291): Add dvbpll i2c device check.

Some cards have multiple possible addresses for their PLLs, with no other
way to tell if a PLL is present or not apart from probing to see if an i2c
device is present. This adds a quick check to see if an i2c device is
present at the given i2c address.

Signed-off-by: Andrew de Quincey <adq_dvb@lidskialf.net>
Acked-by: Michael Krufky <mkrufky@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>

1 files changed, 13 insertions, 0 deletions

diff --git a/drivers/media/dvb/frontends/dvb-pll.c b/drivers/media/dvb/frontends/dvb-pll.c
index a189683454b7..b9a338875948 100644
--- a/drivers/media/dvb/frontends/dvb-pll.c
+++ b/drivers/media/dvb/frontends/dvb-pll.c
@@ -613,7 +613,20 @@ static struct dvb_tuner_ops dvb_pll_tuner_ops = {
 
 int dvb_pll_attach(struct dvb_frontend *fe, int pll_addr, struct i2c_adapter *i2c, struct dvb_pll_desc *desc)
 {
+        u8 b1 [] = { 0 };
+        struct i2c_msg msg [] = { { .addr = pll_addr, .flags = 0, .buf = NULL, .len = 0 },
+                                  { .addr = pll_addr, .flags = I2C_M_RD, .buf = b1, .len = 1 } };
         struct dvb_pll_priv *priv = NULL;
+        int ret;
+
+        if (fe->ops.i2c_gate_ctrl)
+                fe->ops.i2c_gate_ctrl(fe, 1);
+
+        ret = i2c_transfer (i2c, msg, 2);
+        if (ret != 2)
+                return -1;
+        if (fe->ops.i2c_gate_ctrl)
+                     fe->ops.i2c_gate_ctrl(fe, 0);
 
         priv = kzalloc(sizeof(struct dvb_pll_priv), GFP_KERNEL);
         if (priv == NULL)