Hi! On Wed, 7 Aug 2024 at 10:43, Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx> wrote: > Hi, > > On Wed, Aug 07, 2024 at 10:33:51AM +0200, Alexander Stein wrote: > > Hi Benjamin, > > > > Am Mittwoch, 7. August 2024, 10:10:28 CEST schrieb Benjamin Bara: > > > Currently, the V4L2 subdevice is also created when the device is not > > > available/connected. In this case, dmesg shows the following: > > > > > > [ 10.419510] imx290 7-001a: Error writing reg 0x301c: -6 > > > [ 10.428981] imx290 7-001a: Error writing reg 0x3020: -6 > > > [ 10.442712] imx290 7-001a: Error writing reg 0x3018: -6 > > > [ 10.454018] imx290 7-001a: Error writing reg 0x3020: -6 > > > > > > which seems to come from imx290_ctrl_update() after the subdev init is > > > finished. However, as the errors are ignored, the subdev is initialized > > > but simply does not work. From userspace perspective, there is no > > > visible difference between a working and not-working subdevice (except > > > when trying it out or watching for the error message). > > > > > > This commit adds a simple availability check before starting with the > > > subdev initialization to error out instead. > > > > There is already a patch reading the ID register at [1]. This also reads the > > ID register. But I don't have any documentation regarding that register, > > neither address nor values definitions. If there is known information about > > that I would prefer reading the ID and compare it to expected values. > > > > Best regards, > > Alexander > > > > [1] https://gitlab.com/ideasonboard/nxp/linux/-/commit/85ce725f1de7c16133bfb92b2ab0d3d84efcdb47 > > I'd also prefer reading a register and indeed comparing the read value with > the expected value. Sure - I can drop the first patch and check if it contains a "1" (standby). Probably we learn more about the CHIP_ID, then I can switch to it instead. Best regards Benjamin > -- > Regards, > > Sakari Ailus
