Hi Hans, I noticed that there's code in the v4l2 core that enables/disables ioctls and checks some of the parameters depending on the device type. While reading the code an comparing it to the V4L2 API document, some more questions came up: 1) Video devices with VBI functionality: The spec says: "To address the problems of finding related video and VBI devices VBI capturing and output is also available as device function under /dev/video". Is that still valid ? What about VBI "configuration" (e.g. VIDIOC_G/S/TRY_FMT for VBI formats) ? Looking into the v4l2 core code, it seems that the VBI buffer types (field "type" in struct v4l2_format) are only accepted, if the device is a VBI device. 2) VIDIOC_G/S/TRY_FMT and VBI devices: The sepc says: "VBI devices must implement both the VIDIOC_G_FMT and VIDIOC_S_FMT ioctl, even if VIDIOC_S_FMT ignores all requests and always returns default parameters as VIDIOC_G_FMT does. VIDIOC_TRY_FMT is optional." What's the reason for this ? Is it still valid ? 3) VIDIOC_S_TUNER: field "type" in struct v4l2_tuner Are radio tuners accessable through video devices (and the other way around) ? Has this field to be set by the application ? If yes: driver overwrites the value or returns with an error if the type doesn't match the tuner at the requested index ? I wonder if it would make sense to check the tuner type inside the v4l core (like the fmt/buffer type check for G/S_PARM). 4) VIDIOC_DBG_G_CHIP_IDENT: Is it part of CONFIG_VIDEO_ADV_DEBUG just like VIDIOC_DBG_G/S_REGISTER ? In determine_valid_ioctls(), it is placed outside the #ifdef CONFIG_VIDEO_ADV_DEBUG section. The spec says "Identify the chips on a TV card" but isn't it suitable for all device types (radio/video/vbi) ? determine_valid_ioctls() in v4l2-dev.c enables it for all devices. 5) The buffer ioctls (VIDIOC_REQBUFS, VIDIOC_CREATE_BUFS, VIDIOC_PREPARE_BUF, VIDIOC_QUERYBUF, VIDIOC_QBUF, VIDIOC_DQBUF) are not applicable to radio devices, right ? In function determine_valid_ioctls() in v4l2-dev.c they are enabled for all device types. 6) VIDIOC_G/S_AUDIO: Shouldn't it be disabled in determine_valid_ioctls() for VBI devices ? Btw: function determine_valid_ioctls() in v4l2-dev.c is a good summary that explains which ioctls are suitable for which device types (radio/video/vbi). Converting its content into a table would be a great extension/clarifaction of the V4L2 API spec document ! Thanks for your patience ! Regards, Frank -- 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
