Hi Sakari, On Monday 29 June 2015 10:23:34 Sakari Ailus wrote: > Helen Fornazier wrote: > > According to the V4L2 API, the VIDIOC_STREAMON ioctl should return EPIPE > > when the pipeline configuration is invalid. > > > > As the .vidioc_streamon in the v4l2_ioctl_ops usually forwards the error > > caused by the v4l2_subdev_link_validate_default (if it is in use), it > > should return -EPIPE if it detects a format mismatch in the pipeline > > configuration > > Only link configuration errors have yielded -EPIPE so far, sub-device > format configuration error has returned -INVAL instead as you noticed. It should also be noted that while v4l2_subdev_link_validate() will return - EINVAL in case of error, the only driver that performs custom link validation (omap3isp/ispccdc.c) will return -EPIPE. > There are not many sources of -EINVAL while enabling streaming and all > others are directly caused by the application; I lean towards thinking > the code is good as it was. The documentation could be improved though. > It may not be clear which error codes could be caused by different > conditions. > > The debug level messages from media module > (drivers/media/media-entity.c) do provide more information if needed, > albeit this certainly is not an application interface. > > I wonder what others think. There's a discrepancy between the implementation and the documentation, so at least one of them need to be fixed. -EPIPE would be coherent with the documentation and seems appropriately named, but another error code would allow userspace to tell link configuration and format configuration problems apart. Do you think -EINVAL is the most appropriate error code for format configuration ? It's already used to indicate that the stream type is invalid or that not enough buffers have been allocated, and is also used by drivers directly for various purposes. -- Regards, Laurent Pinchart -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
