Hi, On Fri, Jun 10, 2011 at 09:55:13AM +0200, Hans de Goede wrote: > Currently this will cause the usb mass storage driver to see a > disconnect, and any possible still pending writes are lost ... > > This is IMHO unacceptable, but currently there is nothing we can > do to avoid this. > > 2) So called dual mode cameras are (cheap) stillcams often even > without an lcdscreen viewfinder, and battery backed sram instead > of flash, which double as a webcam. We have drivers for both the > stillcam function of these (in libgphoto2, so using usbfs) as > well as for the webcam function (v4l2 kernel drivers). > > These drivers work well, and are mature. Yet the user experience > is rather poor. Under gnome the still-cam contents will be > automatically be made available as a "drive" using a gvfs-gphoto2 fuse > mount. This however involves sending a disconnect to the v4l2 kernel > driver, and thus the /dev/video# node disappearing. So if a user > wants to use the device as a webcam he/she needs to first go to > nautilus and unmount the gvfs mount. Until that is done the user will > simply get a message from an app like cheese that he has no webcam, > not even an ebusy error, just that he has no such device.
that sounds quite weird. Should only happen if still image and video functions are on different configurations or different alt-settings of the same interface. But if they are on same configurations and separate interfaces, you should be able to bind gphoto to the still image interface and v4l2 to the camera interface. How's the device setup ? > So what do we need to make this situation better: > 1) A usb_driver callback alternative to the disconnect callback, > I propose to call this soft_disconnect. This serves 2 purposes > a) It will allow the driver to tell the caller that that is not > a good idea by returning an error code (think usb mass storage > driver and mounted filesystem I'm not sure you even need a driver callback for that. Should we leave that to Desktop manager ? -- balbi
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