Commit 04d8b04e authored by Hans Verkuil's avatar Hans Verkuil Committed by Mauro Carvalho Chehab

[media] v4l2-controls.txt: update to the new way of accessing controls

The way current and new values are accessed has changed. Update the
document to bring it up to date with the code.
Signed-off-by: default avatarHans Verkuil <hans.verkuil@cisco.com>
Reviewed-by: default avatarSylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: default avatarMauro Carvalho Chehab <m.chehab@samsung.com>
parent 680a5139
...@@ -77,9 +77,9 @@ Basic usage for V4L2 and sub-device drivers ...@@ -77,9 +77,9 @@ Basic usage for V4L2 and sub-device drivers
Where foo->v4l2_dev is of type struct v4l2_device. Where foo->v4l2_dev is of type struct v4l2_device.
Finally, remove all control functions from your v4l2_ioctl_ops: Finally, remove all control functions from your v4l2_ioctl_ops (if any):
vidioc_queryctrl, vidioc_querymenu, vidioc_g_ctrl, vidioc_s_ctrl, vidioc_queryctrl, vidioc_query_ext_ctrl, vidioc_querymenu, vidioc_g_ctrl,
vidioc_g_ext_ctrls, vidioc_try_ext_ctrls and vidioc_s_ext_ctrls. vidioc_s_ctrl, vidioc_g_ext_ctrls, vidioc_try_ext_ctrls and vidioc_s_ext_ctrls.
Those are now no longer needed. Those are now no longer needed.
1.3.2) For sub-device drivers do this: 1.3.2) For sub-device drivers do this:
...@@ -258,8 +258,8 @@ The new control value has already been validated, so all you need to do is ...@@ -258,8 +258,8 @@ The new control value has already been validated, so all you need to do is
to actually update the hardware registers. to actually update the hardware registers.
You're done! And this is sufficient for most of the drivers we have. No need You're done! And this is sufficient for most of the drivers we have. No need
to do any validation of control values, or implement QUERYCTRL/QUERYMENU. And to do any validation of control values, or implement QUERYCTRL, QUERY_EXT_CTRL
G/S_CTRL as well as G/TRY/S_EXT_CTRLS are automatically supported. and QUERYMENU. And G/S_CTRL as well as G/TRY/S_EXT_CTRLS are automatically supported.
============================================================================== ==============================================================================
...@@ -288,30 +288,45 @@ of v4l2_device. ...@@ -288,30 +288,45 @@ of v4l2_device.
Accessing Control Values Accessing Control Values
======================== ========================
The v4l2_ctrl struct contains these two unions: The following union is used inside the control framework to access control
values:
union v4l2_ctrl_ptr {
s32 *p_s32;
s64 *p_s64;
char *p_char;
void *p;
};
The v4l2_ctrl struct contains these fields that can be used to access both
current and new values:
/* The current control value. */
union {
s32 val; s32 val;
s64 val64; struct {
char *string; s32 val;
} cur; } cur;
/* The new control value. */
union {
s32 val;
s64 val64;
char *string;
};
Within the control ops you can freely use these. The val and val64 speak for union v4l2_ctrl_ptr p_new;
themselves. The string pointers point to character buffers of length union v4l2_ctrl_ptr p_cur;
If the control has a simple s32 type type, then:
&ctrl->val == ctrl->p_new.p_s32
&ctrl->cur.val == ctrl->p_cur.p_s32
For all other types use ctrl->p_cur.p<something>. Basically the val
and cur.val fields can be considered an alias since these are used so often.
Within the control ops you can freely use these. The val and cur.val speak for
themselves. The p_char pointers point to character buffers of length
ctrl->maximum + 1, and are always 0-terminated. ctrl->maximum + 1, and are always 0-terminated.
In most cases 'cur' contains the current cached control value. When you create Unless the control is marked volatile the p_cur field points to the the
a new control this value is made identical to the default value. After calling current cached control value. When you create a new control this value is made
v4l2_ctrl_handler_setup() this value is passed to the hardware. It is generally identical to the default value. After calling v4l2_ctrl_handler_setup() this
a good idea to call this function. value is passed to the hardware. It is generally a good idea to call this
function.
Whenever a new value is set that new value is automatically cached. This means Whenever a new value is set that new value is automatically cached. This means
that most drivers do not need to implement the g_volatile_ctrl() op. The that most drivers do not need to implement the g_volatile_ctrl() op. The
...@@ -363,7 +378,7 @@ You can also take the handler lock yourself: ...@@ -363,7 +378,7 @@ You can also take the handler lock yourself:
mutex_lock(&state->ctrl_handler.lock); mutex_lock(&state->ctrl_handler.lock);
pr_info("String value is '%s'\n", ctrl1->p_cur.p_char); pr_info("String value is '%s'\n", ctrl1->p_cur.p_char);
printk(KERN_INFO "Integer value is '%s'\n", ctrl2->cur.val); pr_info("Integer value is '%s'\n", ctrl2->cur.val);
mutex_unlock(&state->ctrl_handler.lock); mutex_unlock(&state->ctrl_handler.lock);
......
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