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.
Dave
> + 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)
>
> --
> 2.46.0
>
>
