Em Wed, 01 Jan 2014 19:52:08 +0100
Frank Schäfer <fschaefer.oss@xxxxxxxxxxxxxx> escreveu:
> Am 28.12.2013 13:16, schrieb Mauro Carvalho Chehab:
> > From: Mauro Carvalho Chehab <m.chehab@xxxxxxxxxxx>
> >
> > Instead of using two I2C operations between write and read,
> > use just one i2c_transfer. That allows I2C mutexes to not
> > let any other I2C transfer between the two.
> >
> > Signed-off-by: Mauro Carvalho Chehab <m.chehab@xxxxxxxxxxx>
> > ---
> > drivers/media/i2c/tvp5150.c | 22 ++++++++++------------
> > 1 file changed, 10 insertions(+), 12 deletions(-)
> >
> > diff --git a/drivers/media/i2c/tvp5150.c b/drivers/media/i2c/tvp5150.c
> > index 89c0b13463b7..d6ba457fcf67 100644
> > --- a/drivers/media/i2c/tvp5150.c
> > +++ b/drivers/media/i2c/tvp5150.c
> > @@ -58,21 +58,19 @@ static int tvp5150_read(struct v4l2_subdev *sd, unsigned char addr)
> > struct i2c_client *c = v4l2_get_subdevdata(sd);
> > unsigned char buffer[1];
> > int rc;
> > + struct i2c_msg msg[] = {
> > + { .addr = c->addr, .flags = 0,
> > + .buf = &addr, .len = 1 },
> I would use .buf = buffer here, too.
Why? The address needed is already at addr, and it is also an unsigned char.
Using buffer would require an extra data copy.
>
> > + { .addr = c->addr, .flags = I2C_M_RD,
> > + .buf = buffer, .len = 1 }
> > + };
> >
> > buffer[0] = addr;
> >
> > - rc = i2c_master_send(c, buffer, 1);
> > - if (rc < 0) {
> > - v4l2_err(sd, "i2c i/o error: rc == %d (should be 1)\n", rc);
> > - return rc;
> > - }
> > -
> > - msleep(10);
> That's the critical change.
I don't think so. I'm not sure why I added this at the first place on the
original patch with where I added this driver, but it is very doubtful
that a msleep() is needed here.
This code is really old (from the time I added support for WinTV USB 2).
I suspect I added the sleep there just because the I2C logs, during the
driver development phase, to be an exact mimic on what it was got via
USB dumps.
>
> > -
> > - rc = i2c_master_recv(c, buffer, 1);
> > - if (rc < 0) {
> > - v4l2_err(sd, "i2c i/o error: rc == %d (should be 1)\n", rc);
> > - return rc;
> > + rc = i2c_transfer(c->adapter, msg, 2);
> > + if (rc < 0 || rc != 2) {
> > + v4l2_err(sd, "i2c i/o error: rc == %d (should be 2)\n", rc);
> > + return rc < 0 ? rc : -EIO;
> > }
> >
> > v4l2_dbg(2, debug, sd, "tvp5150: read 0x%02x = 0x%02x\n", addr, buffer[0]);
> Looks good and works without problems with my HVR-900 and WinTV 2
> devices (both em28xx).
>
--
Cheers,
Mauro
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