From 67317e288ea475e9d7d9d9883c4b007aac4ec6a3 Mon Sep 17 00:00:00 2001 From: Hans Verkuil Date: Sun, 6 Sep 2009 13:13:14 +0300 Subject: v4l2-dev: replace 'kernel number' by 'device node number'. From: Hans Verkuil The term 'kernel number' is very vague, so replace it with the somewhat more descriptive term 'device node number'. In one place the local variable 'nr' was used to create the device node number of the new device name. This has been replaced with the vdev->num field to more clearly mark this as being the device node number and not the minor number. Priority: normal Signed-off-by: Hans Verkuil --- linux/Documentation/video4linux/v4l2-framework.txt | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) (limited to 'linux/Documentation/video4linux/v4l2-framework.txt') diff --git a/linux/Documentation/video4linux/v4l2-framework.txt b/linux/Documentation/video4linux/v4l2-framework.txt index cb6c7eb51..38b3716d8 100644 --- a/linux/Documentation/video4linux/v4l2-framework.txt +++ b/linux/Documentation/video4linux/v4l2-framework.txt @@ -486,14 +486,14 @@ VFL_TYPE_RADIO: radioX for radio tuners VFL_TYPE_VTX: vtxX for teletext devices (deprecated, don't use) The last argument gives you a certain amount of control over the device -kernel number used (i.e. the X in videoX). Normally you will pass -1 to +device node number used (i.e. the X in videoX). Normally you will pass -1 to let the v4l2 framework pick the first free number. But if a driver creates many devices, then it can be useful to have different video devices in separate ranges. For example, video capture devices start at 0, video output devices start at 16. -So you can use the last argument to specify a minimum kernel number and -the v4l2 framework will try to pick the first free number that is equal +So you can use the last argument to specify a minimum device node number +and the v4l2 framework will try to pick the first free number that is equal or higher to what you passed. If that fails, then it will just pick the first free number. @@ -513,7 +513,7 @@ After the device was successfully registered, then you can use these fields: - vfl_type: the device type passed to video_register_device. - minor: the assigned device minor number. -- num: the device kernel number (i.e. the X in videoX). +- num: the device node number (i.e. the X in videoX). - index: the device index number. If the registration failed, then you need to call video_device_release() -- cgit v1.2.3 From 856378592a1b9be61e28092caf5e87446bae4694 Mon Sep 17 00:00:00 2001 From: Hans Verkuil Date: Sun, 6 Sep 2009 13:54:00 +0300 Subject: v4l: warn when desired devnodenr is in use & add _no_warn function From: Hans Verkuil Warn when the desired device node number is already in use, except when the new video_register_device_no_warn function is called since in some use-cases that warning is not relevant. Priority: normal Signed-off-by: Hans Verkuil --- linux/Documentation/video4linux/v4l2-framework.txt | 22 ++++++++++++++++------ 1 file changed, 16 insertions(+), 6 deletions(-) (limited to 'linux/Documentation/video4linux/v4l2-framework.txt') diff --git a/linux/Documentation/video4linux/v4l2-framework.txt b/linux/Documentation/video4linux/v4l2-framework.txt index 38b3716d8..b806edaf3 100644 --- a/linux/Documentation/video4linux/v4l2-framework.txt +++ b/linux/Documentation/video4linux/v4l2-framework.txt @@ -486,17 +486,27 @@ VFL_TYPE_RADIO: radioX for radio tuners VFL_TYPE_VTX: vtxX for teletext devices (deprecated, don't use) The last argument gives you a certain amount of control over the device -device node number used (i.e. the X in videoX). Normally you will pass -1 to -let the v4l2 framework pick the first free number. But if a driver creates -many devices, then it can be useful to have different video devices in -separate ranges. For example, video capture devices start at 0, video -output devices start at 16. - +device node number used (i.e. the X in videoX). Normally you will pass -1 +to let the v4l2 framework pick the first free number. But sometimes users +want to select a specific node number. It is common that drivers allow +the user to select a specific device node number through a driver module +option. That number is then passed to this function and video_register_device +will attempt to select that device node number. If that number was already +in use, then the next free device node number will be selected and it +will send a warning to the kernel log. + +Another use-case is if a driver creates many devices. In that case it can +be useful to place different video devices in separate ranges. For example, +video capture devices start at 0, video output devices start at 16. So you can use the last argument to specify a minimum device node number and the v4l2 framework will try to pick the first free number that is equal or higher to what you passed. If that fails, then it will just pick the first free number. +Since in this case you do not care about a warning about not being able +to select the specified device node number, you can call the function +video_register_device_no_warn() instead. + Whenever a device node is created some attributes are also created for you. If you look in /sys/class/video4linux you see the devices. Go into e.g. video0 and you will see 'name' and 'index' attributes. The 'name' attribute -- cgit v1.2.3