Re: [ragnatech:media-tree 2075/2144] drivers/media/dvb-frontends/stv0910.c:1185:2-8: preceding lock on line 1176 (fwd)

[Daniel Scheller <d.scheller@xxxxxxx>]

Hello Jula,

Am 24.07.2017 um 07:02 schrieb Julia Lawall:

> Is a lock release needed before line 1185?  Is the !enable in line 1189
> correct?  If the code is correct as is, perhaps it could be good to add
> some comments.

Yes, it's needed because the I2C gate is shared for the two tuner chips 
attached to it (one dual-demod chip -> two tuners/SECs) and the bus 
access needs to be protected to not accidentally interfere when 
accessing both tuners in parallel.

I'll think about proper comments there.

Thanks,
Daniel

> ---------- Forwarded message ----------
> Date: Mon, 24 Jul 2017 12:55:30 +0800
> From: kbuild test robot <fengguang.wu@xxxxxxxxx>
> To: kbuild@xxxxxx
> Cc: Julia Lawall <julia.lawall@xxxxxxx>
> Subject: [ragnatech:media-tree 2075/2144]
>      drivers/media/dvb-frontends/stv0910.c:1185:2-8: preceding lock on line 1176
>
> CC: kbuild-all@xxxxxx
> TO: Daniel Scheller <d.scheller@xxxxxxx>
> CC: Mauro Carvalho Chehab <m.chehab@xxxxxxxxxxx>
> CC: linux-media@xxxxxxxxxxxxxxx
>
> tree:   git://git.ragnatech.se/linux media-tree
> head:   0e50e84a11f4854e9a7e3b7f4443ffb99e6be292
> commit: cd21b334943719f880e707eb91895fc916a88000 [2075/2144] media: dvb-frontends: add ST STV0910 DVB-S/S2 demodulator frontend driver
> :::::: branch date: 3 days ago
> :::::: commit date: 4 days ago
>
> > > drivers/media/dvb-frontends/stv0910.c:1185:2-8: preceding lock on line 1176
>
> git remote add ragnatech git://git.ragnatech.se/linux
> git remote update ragnatech
> git checkout cd21b334943719f880e707eb91895fc916a88000
> vim +1185 drivers/media/dvb-frontends/stv0910.c
>
> cd21b334 Daniel Scheller 2017-07-03  1168
> cd21b334 Daniel Scheller 2017-07-03  1169
> cd21b334 Daniel Scheller 2017-07-03  1170  static int gate_ctrl(struct dvb_frontend *fe, int enable)
> cd21b334 Daniel Scheller 2017-07-03  1171  {
> cd21b334 Daniel Scheller 2017-07-03  1172  	struct stv *state = fe->demodulator_priv;
> cd21b334 Daniel Scheller 2017-07-03  1173  	u8 i2crpt = state->i2crpt & ~0x86;
> cd21b334 Daniel Scheller 2017-07-03  1174
> cd21b334 Daniel Scheller 2017-07-03  1175  	if (enable)
> cd21b334 Daniel Scheller 2017-07-03 @1176  		mutex_lock(&state->base->i2c_lock);
> cd21b334 Daniel Scheller 2017-07-03  1177
> cd21b334 Daniel Scheller 2017-07-03  1178  	if (enable)
> cd21b334 Daniel Scheller 2017-07-03  1179  		i2crpt |= 0x80;
> cd21b334 Daniel Scheller 2017-07-03  1180  	else
> cd21b334 Daniel Scheller 2017-07-03  1181  		i2crpt |= 0x02;
> cd21b334 Daniel Scheller 2017-07-03  1182
> cd21b334 Daniel Scheller 2017-07-03  1183  	if (write_reg(state, state->nr ? RSTV0910_P2_I2CRPT :
> cd21b334 Daniel Scheller 2017-07-03  1184  		      RSTV0910_P1_I2CRPT, i2crpt) < 0)
> cd21b334 Daniel Scheller 2017-07-03 @1185  		return -EIO;
> cd21b334 Daniel Scheller 2017-07-03  1186
> cd21b334 Daniel Scheller 2017-07-03  1187  	state->i2crpt = i2crpt;
> cd21b334 Daniel Scheller 2017-07-03  1188
> cd21b334 Daniel Scheller 2017-07-03  1189  	if (!enable)
> cd21b334 Daniel Scheller 2017-07-03  1190  		mutex_unlock(&state->base->i2c_lock);
> cd21b334 Daniel Scheller 2017-07-03  1191  	return 0;
> cd21b334 Daniel Scheller 2017-07-03  1192  }
> cd21b334 Daniel Scheller 2017-07-03  1193
>
> ---
> 0-DAY kernel test infrastructure                Open Source Technology Center
> https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

Best regards,
Daniel Scheller
--
https://github.com/herrnst