diff options
| author | Daniel Scheller <d.scheller@gmx.net> | 2017-08-23 19:09:58 +0300 |
|---|---|---|
| committer | Mauro Carvalho Chehab <mchehab@s-opensource.com> | 2017-08-27 13:35:13 +0300 |
| commit | 6b852620fa75d3137929538b4a9aec2f953ff03c (patch) | |
| tree | cba4ee9ccc44b17acfe77d73505ec92709cd74f7 /drivers/media | |
| parent | e59eb4adf0d79fe7692c08c07445ec9efc8ddc1c (diff) | |
| download | linux-6b852620fa75d3137929538b4a9aec2f953ff03c.tar.xz | |
media: dvb-frontends/stv0910: release lock on gate_ctrl() failure
Whenever write_reg() fails to open/close the demod's I2C gate, release the
lock to avoid deadlocking situations. If I2c gate open failed, there's no
need to hold a lock, and if close fails, the mutex_unlock() at the end of
the function is never reached, leaving the mutex_lock in locked state,
which in turn will cause potential for deadlocks. Thus, release the lock
on failure.
While we're touching gate_ctrl(), add some explanation about the need for
locking and the shared I2C bus/gate.
Cc: Julia Lawall <julia.lawall@lip6.fr>
Signed-off-by: Daniel Scheller <d.scheller@gmx.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Diffstat (limited to 'drivers/media')
| -rw-r--r-- | drivers/media/dvb-frontends/stv0910.c | 25 |
1 files changed, 20 insertions, 5 deletions
diff --git a/drivers/media/dvb-frontends/stv0910.c b/drivers/media/dvb-frontends/stv0910.c index d1ae9553f74c..0d4a6a115159 100644 --- a/drivers/media/dvb-frontends/stv0910.c +++ b/drivers/media/dvb-frontends/stv0910.c @@ -1221,17 +1221,32 @@ static int gate_ctrl(struct dvb_frontend *fe, int enable) struct stv *state = fe->demodulator_priv; u8 i2crpt = state->i2crpt & ~0x86; - if (enable) - mutex_lock(&state->base->i2c_lock); + /* + * mutex_lock note: Concurrent I2C gate bus accesses must be + * prevented (STV0910 = dual demod on a single IC with a single I2C + * gate/bus, and two tuners attached), similar to most (if not all) + * other I2C host interfaces/busses. + * + * enable=1 (open I2C gate) will grab the lock + * enable=0 (close I2C gate) releases the lock + */ - if (enable) + if (enable) { + mutex_lock(&state->base->i2c_lock); i2crpt |= 0x80; - else + } else { i2crpt |= 0x02; + } if (write_reg(state, state->nr ? RSTV0910_P2_I2CRPT : - RSTV0910_P1_I2CRPT, i2crpt) < 0) + RSTV0910_P1_I2CRPT, i2crpt) < 0) { + /* don't hold the I2C bus lock on failure */ + mutex_unlock(&state->base->i2c_lock); + dev_err(&state->base->i2c->dev, + "%s() write_reg failure (enable=%d)\n", + __func__, enable); return -EIO; + } state->i2crpt = i2crpt; |