On Mon, Sep 02, 2024 at 07:22:43PM +0100, Dave Stevenson wrote: > Hi Benjamin > > On Mon, 2 Sept 2024 at 16:58, <bbara93@xxxxxxxxx> wrote: > > > > From: Benjamin Bara <benjamin.bara@xxxxxxxxxxx> > > > > Currently, the V4L2 subdevice is also created when the device is not > > available/connected. From userspace perspective, there is no visible > > difference between a working and not-working subdevice (except when > > trying it out). > > > > This commit adds a simple availability check before starting with the > > subdev initialization to error out instead. > > > > Signed-off-by: Benjamin Bara <benjamin.bara@xxxxxxxxxxx> > > --- > > Changes since v2: > > - the new 1/8 is split out > > - use dev_err_probe() (thx Laurent) > > --- > > drivers/media/i2c/imx290.c | 12 ++++++++++++ > > 1 file changed, 12 insertions(+) > > > > diff --git a/drivers/media/i2c/imx290.c b/drivers/media/i2c/imx290.c > > index 9610e9fd2059..6b292bbb0856 100644 > > --- a/drivers/media/i2c/imx290.c > > +++ b/drivers/media/i2c/imx290.c > > @@ -1571,6 +1571,7 @@ static int imx290_probe(struct i2c_client *client) > > { > > struct device *dev = &client->dev; > > struct imx290 *imx290; > > + u64 val; > > int ret; > > > > imx290 = devm_kzalloc(dev, sizeof(*imx290), GFP_KERNEL); > > @@ -1631,6 +1632,17 @@ static int imx290_probe(struct i2c_client *client) > > pm_runtime_set_autosuspend_delay(dev, 1000); > > pm_runtime_use_autosuspend(dev); > > > > + /* Make sure the sensor is available before V4L2 subdev init. */ > > + ret = cci_read(imx290->regmap, IMX290_STANDBY, &val, NULL); > > + if (ret) { > > + ret = dev_err_probe(dev, -ENODEV, "Failed to detect sensor\n"); > > + goto err_pm; > > + } > > + if (val != IMX290_STANDBY_STANDBY) { > > As Laurent commented on v2, this is a slightly unsafe check. If the > device isn't controlled via a regulator then there's no guarantee that > the sensor will be in standby. > The cci_read call will already have returned an error if the sensor > isn't present which will be 99.999% of the error cases. > > If you want to catch the case where it's not in standby, why not put > it into standby as a recovery mechanism. It'd be a better user > experience than just bombing out of the probe. I would also just drop the value check. I don't think it would really catch real world issues. > > + ret = dev_err_probe(dev, -ENODEV, "Sensor is not in standby\n"); > > + goto err_pm; > > + } > > + > > /* Initialize the V4L2 subdev. */ > > ret = imx290_subdev_init(imx290); > > if (ret) -- Regards, Laurent Pinchart