Gerd Knorr wrote: > > > Allowing multiple opens in the API does'nt mean that all drivers must > > > support it. I think this should be up to the driver. IMHO it should > > > be allowed for drivers to support single opens only like todays v4l1 > > > drivers do. > > > > This is allowed in the API as is currently specced. > > Yes, of course. Last time I got responses along the lines "multiple opens > makes driver writing harder, that's why it is bad". That's why I wanted > make clear that supporting multiple opens isn't mandatory for the drivers. Well, it does support multiple opens, but it is spec'd that only one open can have capturing privileges. Multiple capturing opens can produce subtle repercussions in the sematics of various ioctls. For example, suppose an app opens a driver and does a GET-FORMAT (or any other kind of query) while there are two capturing opens active. The format of which open should be returned? If the driver requires both opens to use the same format, which open gets control, and will that mess up the app that doesn't have control? Of course, a driver writer can do whatever he pleases behind the scenes, as long the ioctl semantics are preserved such that apps, and therefore users, are happy. Bill.
