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Commit 6b852620 authored by Daniel Scheller's avatar Daniel Scheller Committed by Mauro Carvalho Chehab
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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: default avatarDaniel Scheller <d.scheller@gmx.net>
Signed-off-by: default avatarMauro Carvalho Chehab <mchehab@s-opensource.com>
parent e59eb4ad

drivers/media/dvb-frontends/stv0910.c

+20 −5
Original line number Original line Diff line number Diff line
@@ -1221,17 +1221,32 @@ static int gate_ctrl(struct dvb_frontend *fe, int enable) 
	struct stv *state = fe->demodulator_priv;

	struct stv *state = fe->demodulator_priv;

	u8 i2crpt = state->i2crpt & ~0x86;

	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;

		i2crpt |= 0x80;

	else

	} else {

		i2crpt |= 0x02;

		i2crpt |= 0x02;

	}





	if (write_reg(state, state->nr ? RSTV0910_P2_I2CRPT :

	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;

		return -EIO;

	}





	state->i2crpt = i2crpt;

	state->i2crpt = i2crpt;