Re: [media] duplicate code in media drivers

[Gustavo A. R. Silva]

Mauro,

I already sent some patches based on your comments.

Thanks!
--
Gustavo

On 05/21/2018 03:14 PM, Mauro Carvalho Chehab wrote:
> Em Mon, 21 May 2018 14:39:51 -0500
> "Gustavo A. R. Silva" <gustavo@xxxxxxxxxxxxxx> escreveu:
>
> > Hi Mauro,
> >
> > I found some duplicate code with the help of Coccinelle and Coverity. Notice that these are not code patches, they only point out the duplicate code in some media drivers:
> >
> > diff -u -p drivers/media/pci/bt8xx/dvb-bt8xx.c /tmp/nothing/media/pci/bt8xx/dvb-bt8xx.c
> > --- drivers/media/pci/bt8xx/dvb-bt8xx.c
> > +++ /tmp/nothing/media/pci/bt8xx/dvb-bt8xx.c
> > @@ -389,9 +389,7 @@ static int advbt771_samsung_tdtc9251dh0_
> >          else if (c->frequency < 600000000)
> >                  bs = 0x08;
> >          else if (c->frequency < 730000000)
> > -               bs = 0x08;
> >          else
> > -               bs = 0x08;
> >
> >          pllbuf[0] = 0x61;
> >          pllbuf[1] = div >> 8;
>
>
> Hmm... I *suspect* that "bs" here controls the frequency range for the
> tuner. Analog tuners have separate frequency regions that are controlled
> via a register, into a 4 or 5 bytes I2C sequence. They're all somewhat
> a clone of an old Philips design.
>
> It should be safe to convert the "BS" sequence on something like:
>
> 	if (c->frequency < 173000000)
>                  bs = 0x01;
>          else if (c->frequency < 470000000)
>                  bs = 0x02;
>          else
>                  bs = 0x08;
>
>
>
> > diff -u -p drivers/media/usb/dvb-usb/dib0700_devices.c /tmp/nothing/media/usb/dvb-usb/dib0700_devices.c
> > --- drivers/media/usb/dvb-usb/dib0700_devices.c
> > +++ /tmp/nothing/media/usb/dvb-usb/dib0700_devices.c
> > @@ -1741,13 +1741,6 @@ static int dib809x_tuner_attach(struct d
> >          struct dib0700_adapter_state *st = adap->priv;
> >          struct i2c_adapter *tun_i2c = st->dib8000_ops.get_i2c_master(adap->fe_adap[0].fe, DIBX000_I2C_INTERFACE_TUNER, 1);
> >
> > -       if (adap->id == 0) {
> > -               if (dvb_attach(dib0090_register, adap->fe_adap[0].fe, tun_i2c, &dib809x_dib0090_config) == NULL)
> > -                       return -ENODEV;
> > -       } else {
> > -               if (dvb_attach(dib0090_register, adap->fe_adap[0].fe, tun_i2c, &dib809x_dib0090_config) == NULL)
> > -                       return -ENODEV;
> > -       }
>
> I'm almost sure that, on the second if, it should be adap->fe_adap[1].fe.
> I tried in the past to check this, but didn't got an answer from the one
> that wrote the code.
>
> Maybe we could add a /* FIXME: check if it is fe_adap[1] */ on the
> second clause.
>
> >          st->set_param_save = adap->fe_adap[0].fe->ops.tuner_ops.set_params;
> >          adap->fe_adap[0].fe->ops.tuner_ops.set_params = dib8096_set_param_override;
> > diff -u -p drivers/media/dvb-frontends/mb86a16.c /tmp/nothing/media/dvb-frontends/mb86a16.c
> > --- drivers/media/dvb-frontends/mb86a16.c
> > +++ /tmp/nothing/media/dvb-frontends/mb86a16.c
> > @@ -1466,9 +1466,7 @@ static int mb86a16_set_fe(struct mb86a16
> >                                                          wait_t = (1572864 + state->srate / 2) / state->srate;
> >                                                  if (state->srate < 5000)
> >                                                          /* FIXME ! , should be a long wait ! */
> > -                                                       msleep_interruptible(wait_t);
> >                                                  else
> > -                                                       msleep_interruptible(wait_t);
>
> I suspect that the goal here is to point that sleeping for
> (1572864 + state->srate / 2) / state->srate when srate is low will mean
> that it will take a lot of time to converge (probably causing timeout at
> userspace).
>
> Basically, if srate is < 5000, the sleep time will be between
> 314 and 1575364 ms. The worse case scenario - although not realistic,
> in practice - is to wait up to 26 seconds. This is a very long time!
>
> Probably, the right fix here would be to check if wait_t is bigger than
> a certain amount of time. If so, return an error.
>
> I'm not against removing the if, but, if so, better to add a /* FIXME */
> block explaining that.
>
> That's said, this is an old device. I doubt anyone would fix it.
>
>
> >                                                  if (sync_chk(state, &junk) == 0) {
> >                                                          iq_vt_set(state, 1);
> > diff -u -p drivers/media/dvb-frontends/au8522_decoder.c /tmp/nothing/media/dvb-frontends/au8522_decoder.c
> > --- drivers/media/dvb-frontends/au8522_decoder.c
> > +++ /tmp/nothing/media/dvb-frontends/au8522_decoder.c
> > @@ -280,14 +280,9 @@ static void setup_decoder_defaults(struc
> >                          AU8522_TOREGAAGC_REG0E5H_CVBS);
> >          au8522_writereg(state, AU8522_REG016H, AU8522_REG016H_CVBS);
> >
> > -       if (is_svideo) {
> >                  /* Despite what the table says, for the HVR-950q we still need
> >                     to be in CVBS mode for the S-Video input (reason unknown). */
> >                  /* filter_coef_type = 3; */
> > -               filter_coef_type = 5;
> > -       } else {
> > -               filter_coef_type = 5;
> > -       }
>
> Better ask Devin about this (c/c).
>
> >          /* Load the Video Decoder Filter Coefficients */
> >          for (i = 0; i < NUM_FILTER_COEF; i++) {
> >
> >
> > I wonder if some of the cases above were intentionally coded that way or some code needs to be removed.
> >
> > Thanks
> > --
> > Gustavo
>
>
>
> Thanks,
> Mauro