On 8/10/20 10:27 PM, Sakari Ailus wrote: > Hi all, > ...snip... > > The use case is such that there is a privacy LED next to an integrated > user-facing laptop camera, and this LED is there to signal the user that > the camera is recording a video or capturing images. That LED also happens > to be wired to one of the power supplies of the camera, so whenever you > power on the camera, the LED will be lit, whether images are captured from > the camera --- or not. There's no way to implement this differently > without additional software control (allowing of which is itself a > hardware design decision) on most CSI-2-connected camera sensors as they > simply have no pin to signal the camera streaming state. > > This is also what happens during driver probe: the camera will be powered > on by the I²C subsystem calling dev_pm_domain_attach() and the device is > already powered on when the driver's own probe function is called. To the > user this visible during the boot process as a blink of the privacy LED, > suggesting that the camera is recording without the user having used an > application to do that. From the end user's point of view the behaviour is > not expected and for someone unfamiliar with internal workings of a > computer surely seems quite suspicious --- even if images are not being > actually captured. > > I've tested these on linux-next master. They also apply to Wolfram's > i2c/for-next branch, there's a patch that affects the I²C core changes > here (see below). The patches apart from that apply to Bartosz's > at24/for-next as well as Mauro's linux-media master branch. Sakari, we meet one issue - once the vcm sub-device registered, the user space will try to open the VCM (I have not figure out who did that), it will also trigger the acpi pm resume/suspend, as the VCM always shares same power rail with camera sensor, so the privacy LED still has a blink. > ...snip... -- Best regards, Bingbu Cao
