On Mon, Oct 17, 2022 at 12:03:17AM +0300, Laurent Pinchart wrote: > Hi Sakari, > > On Sun, Oct 16, 2022 at 08:19:40PM +0000, Sakari Ailus wrote: > > On Sun, Oct 16, 2022 at 02:23:13AM +0300, Laurent Pinchart wrote: > > > On Sat, Oct 15, 2022 at 09:35:12PM +0000, Sakari Ailus wrote: > > > > On Sat, Oct 15, 2022 at 09:25:37AM +0300, Laurent Pinchart wrote: > > > > > On Fri, Oct 14, 2022 at 07:34:58PM +0100, Prabhakar wrote: > > > > > > From: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx> > > > > > > > > > > > > Always return zero while stopping the stream as the caller will ignore the > > > > > > return value. > > > > > > > > > > > > This patch drops checking the return value of ov5645_write_reg() and > > > > > > continues further in the code path while stopping stream. The user anyway > > > > > > gets an error message in case ov5645_write_reg() fails. > > > > > > > > > > Continuing all the way to pm_runtime_put() is fine, but I don't think > > > > > the function should return 0. It's not up to the driver to decide if a > > > > > failure would be useful to signal to the caller or not. > > > > > > > > If the function returns an error when disabling streaming, what is the > > > > expected power state of the device after this? > > > > > > That's up to us to decide :-) > > > > > > > The contract between the caller and the callee is that the state is not > > > > changed if there is an error. > > > > > > For most APIs, but that's not universal. > > > > > > > This is a special case as very few callers > > > > check the return value for streamoff operation and those that do generally > > > > just print something. I've never seen a caller trying to prevent streaming > > > > off in this case, for instance. > > > > > > I think the stream off call should proceed and try to power off the > > > device even if an error occurs along the way, i.e. it shouldn't return > > > upon the first detected error. > > > > > > > Of course we could document that streaming off always counts as succeeded > > > > (e.g. decreasing device's runtime PM usage_count) while it could return an > > > > informational error code. But I wonder if anyone would ever benefit from > > > > that somehow. :-) > > > > > > I think it could be useful to propagate errors up to inform the user > > > that something wrong happened. That would involve fixing lots of drivers > > > along the call chain though, so there's no urgency for the ov5645 to do > > > so, but isn't it better to propagate the error code instead of hiding > > > the issue ? > > > > I also don't think hiding the issue would be the best thing to do, but that > > wouldn't likely be a big problem either. > > > > How about printing a warning in the wrapper while returning zero to the > > original caller? This would keep the API intact while still leaving a trace > > on something failing. Of course the driver is also free to print whatever > > messages it likes. > > While I think error propagation could be more useful in the long run, > printing a message in the wrapper is a good idea. I like centralized > error handling, it has a tendency to go wrong when left to individual > drivers. I can send a patch... -- Sakari Ailus
