Re: [PATCH v9 10/15] media: uapi: Add V4L2_CTRL_TYPE_FIXED_POINT

[Hans Verkuil <hverkuil@xs4all.nl>]

Here is an RFC patch adding support for 'fraction_bits'. It's lacking
documentation, but it can be used for testing.

It was rather a pain logging fixed point number in a reasonable format,
but I think it is OK.

In userspace (where you can use floating point) it is a lot easier:

printf("%.*g\n", fraction_bits, (double)v * (1.0 / (1ULL << fraction_bits)));

I decided to only expose fraction_bits in struct v4l2_query_ext_ctrl.
I could add it to struct v4l2_queryctrl, but I did not think that was
necessary. Other opinions are welcome.

In the meantime, let me know if this works for your patch series. If it
does, then I can clean this up.

Regards,

	Hans

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
---
 drivers/media/v4l2-core/v4l2-ctrls-api.c  |  1 +
 drivers/media/v4l2-core/v4l2-ctrls-core.c | 72 +++++++++++++++++++----
 include/media/v4l2-ctrls.h                |  7 ++-
 include/uapi/linux/videodev2.h            | 20 ++++++-
 4 files changed, 85 insertions(+), 15 deletions(-)

diff --git a/drivers/media/v4l2-core/v4l2-ctrls-api.c b/drivers/media/v4l2-core/v4l2-ctrls-api.c
index 002ea6588edf..3132df315b17 100644
--- a/drivers/media/v4l2-core/v4l2-ctrls-api.c
+++ b/drivers/media/v4l2-core/v4l2-ctrls-api.c
@@ -1101,6 +1101,7 @@ int v4l2_query_ext_ctrl(struct v4l2_ctrl_handler *hdl, struct v4l2_query_ext_ctr
 	qc->elems = ctrl->elems;
 	qc->nr_of_dims = ctrl->nr_of_dims;
 	memcpy(qc->dims, ctrl->dims, qc->nr_of_dims * sizeof(qc->dims[0]));
+	qc->fraction_bits = ctrl->fraction_bits;
 	qc->minimum = ctrl->minimum;
 	qc->maximum = ctrl->maximum;
 	qc->default_value = ctrl->default_value;
diff --git a/drivers/media/v4l2-core/v4l2-ctrls-core.c b/drivers/media/v4l2-core/v4l2-ctrls-core.c
index a662fb60f73f..0e08a371af5c 100644
--- a/drivers/media/v4l2-core/v4l2-ctrls-core.c
+++ b/drivers/media/v4l2-core/v4l2-ctrls-core.c
@@ -252,12 +252,42 @@ void v4l2_ctrl_type_op_init(const struct v4l2_ctrl *ctrl, u32 from_idx,
 }
 EXPORT_SYMBOL(v4l2_ctrl_type_op_init);

+static void v4l2_ctrl_log_fp(s64 v, unsigned int fraction_bits)
+{
+	s64 i = v4l2_fp_integer(v, fraction_bits);
+	s64 f = v4l2_fp_fraction(v, fraction_bits);
+
+	if (!f) {
+		pr_cont("%lld", i);
+	} else if (fraction_bits < 20) {
+		u64 div = 1ULL << fraction_bits;
+
+		if (!i && f < 0)
+			pr_cont("-%lld/%llu", -f, div);
+		else if (!i)
+			pr_cont("%lld/%llu", f, div);
+		else if (i < 0 || f < 0)
+			pr_cont("-%lld-%llu/%llu", -i, -f, div);
+		else
+			pr_cont("%lld+%llu/%llu", i, f, div);
+	} else {
+		if (!i && f < 0)
+			pr_cont("-%lld/(2^%u)", -f, fraction_bits);
+		else if (!i)
+			pr_cont("%lld/(2^%u)", f, fraction_bits);
+		else if (i < 0 || f < 0)
+			pr_cont("-%lld-%llu/(2^%u)", -i, -f, fraction_bits);
+		else
+			pr_cont("%lld+%llu/(2^%u)", i, f, fraction_bits);
+	}
+}
+
 void v4l2_ctrl_type_op_log(const struct v4l2_ctrl *ctrl)
 {
 	union v4l2_ctrl_ptr ptr = ctrl->p_cur;

 	if (ctrl->is_array) {
-		unsigned i;
+		unsigned int i;

 		for (i = 0; i < ctrl->nr_of_dims; i++)
 			pr_cont("[%u]", ctrl->dims[i]);
@@ -266,7 +296,10 @@ void v4l2_ctrl_type_op_log(const struct v4l2_ctrl *ctrl)

 	switch (ctrl->type) {
 	case V4L2_CTRL_TYPE_INTEGER:
-		pr_cont("%d", *ptr.p_s32);
+		if (!ctrl->fraction_bits)
+			pr_cont("%d", *ptr.p_s32);
+		else
+			v4l2_ctrl_log_fp(*ptr.p_s32, ctrl->fraction_bits);
 		break;
 	case V4L2_CTRL_TYPE_BOOLEAN:
 		pr_cont("%s", *ptr.p_s32 ? "true" : "false");
@@ -281,19 +314,31 @@ void v4l2_ctrl_type_op_log(const struct v4l2_ctrl *ctrl)
 		pr_cont("0x%08x", *ptr.p_s32);
 		break;
 	case V4L2_CTRL_TYPE_INTEGER64:
-		pr_cont("%lld", *ptr.p_s64);
+		if (!ctrl->fraction_bits)
+			pr_cont("%lld", *ptr.p_s64);
+		else
+			v4l2_ctrl_log_fp(*ptr.p_s64, ctrl->fraction_bits);
 		break;
 	case V4L2_CTRL_TYPE_STRING:
 		pr_cont("%s", ptr.p_char);
 		break;
 	case V4L2_CTRL_TYPE_U8:
-		pr_cont("%u", (unsigned)*ptr.p_u8);
+		if (!ctrl->fraction_bits)
+			pr_cont("%u", (unsigned int)*ptr.p_u8);
+		else
+			v4l2_ctrl_log_fp((unsigned int)*ptr.p_u8, ctrl->fraction_bits);
 		break;
 	case V4L2_CTRL_TYPE_U16:
-		pr_cont("%u", (unsigned)*ptr.p_u16);
+		if (!ctrl->fraction_bits)
+			pr_cont("%u", (unsigned int)*ptr.p_u16);
+		else
+			v4l2_ctrl_log_fp((unsigned int)*ptr.p_u16, ctrl->fraction_bits);
 		break;
 	case V4L2_CTRL_TYPE_U32:
-		pr_cont("%u", (unsigned)*ptr.p_u32);
+		if (!ctrl->fraction_bits)
+			pr_cont("%u", (unsigned int)*ptr.p_u32);
+		else
+			v4l2_ctrl_log_fp((unsigned int)*ptr.p_u32, ctrl->fraction_bits);
 		break;
 	case V4L2_CTRL_TYPE_H264_SPS:
 		pr_cont("H264_SPS");
@@ -1752,7 +1797,7 @@ static struct v4l2_ctrl *v4l2_ctrl_new(struct v4l2_ctrl_handler *hdl,
 			u32 id, const char *name, enum v4l2_ctrl_type type,
 			s64 min, s64 max, u64 step, s64 def,
 			const u32 dims[V4L2_CTRL_MAX_DIMS], u32 elem_size,
-			u32 flags, const char * const *qmenu,
+			u32 fraction_bits, u32 flags, const char * const *qmenu,
 			const s64 *qmenu_int, const union v4l2_ctrl_ptr p_def,
 			void *priv)
 {
@@ -1939,6 +1984,7 @@ static struct v4l2_ctrl *v4l2_ctrl_new(struct v4l2_ctrl_handler *hdl,
 	ctrl->name = name;
 	ctrl->type = type;
 	ctrl->flags = flags;
+	ctrl->fraction_bits = fraction_bits;
 	ctrl->minimum = min;
 	ctrl->maximum = max;
 	ctrl->step = step;
@@ -2037,7 +2083,7 @@ struct v4l2_ctrl *v4l2_ctrl_new_custom(struct v4l2_ctrl_handler *hdl,
 	ctrl = v4l2_ctrl_new(hdl, cfg->ops, cfg->type_ops, cfg->id, name,
 			type, min, max,
 			is_menu ? cfg->menu_skip_mask : step, def,
-			cfg->dims, cfg->elem_size,
+			cfg->dims, cfg->elem_size, cfg->fraction_bits,
 			flags, qmenu, qmenu_int, cfg->p_def, priv);
 	if (ctrl)
 		ctrl->is_private = cfg->is_private;
@@ -2062,7 +2108,7 @@ struct v4l2_ctrl *v4l2_ctrl_new_std(struct v4l2_ctrl_handler *hdl,
 		return NULL;
 	}
 	return v4l2_ctrl_new(hdl, ops, NULL, id, name, type,
-			     min, max, step, def, NULL, 0,
+			     min, max, step, def, NULL, 0, 0,
 			     flags, NULL, NULL, ptr_null, NULL);
 }
 EXPORT_SYMBOL(v4l2_ctrl_new_std);
@@ -2095,7 +2141,7 @@ struct v4l2_ctrl *v4l2_ctrl_new_std_menu(struct v4l2_ctrl_handler *hdl,
 		return NULL;
 	}
 	return v4l2_ctrl_new(hdl, ops, NULL, id, name, type,
-			     0, max, mask, def, NULL, 0,
+			     0, max, mask, def, NULL, 0, 0,
 			     flags, qmenu, qmenu_int, ptr_null, NULL);
 }
 EXPORT_SYMBOL(v4l2_ctrl_new_std_menu);
@@ -2127,7 +2173,7 @@ struct v4l2_ctrl *v4l2_ctrl_new_std_menu_items(struct v4l2_ctrl_handler *hdl,
 		return NULL;
 	}
 	return v4l2_ctrl_new(hdl, ops, NULL, id, name, type,
-			     0, max, mask, def, NULL, 0,
+			     0, max, mask, def, NULL, 0, 0,
 			     flags, qmenu, NULL, ptr_null, NULL);

 }
@@ -2149,7 +2195,7 @@ struct v4l2_ctrl *v4l2_ctrl_new_std_compound(struct v4l2_ctrl_handler *hdl,
 		return NULL;
 	}
 	return v4l2_ctrl_new(hdl, ops, NULL, id, name, type,
-			     min, max, step, def, NULL, 0,
+			     min, max, step, def, NULL, 0, 0,
 			     flags, NULL, NULL, p_def, NULL);
 }
 EXPORT_SYMBOL(v4l2_ctrl_new_std_compound);
@@ -2173,7 +2219,7 @@ struct v4l2_ctrl *v4l2_ctrl_new_int_menu(struct v4l2_ctrl_handler *hdl,
 		return NULL;
 	}
 	return v4l2_ctrl_new(hdl, ops, NULL, id, name, type,
-			     0, max, 0, def, NULL, 0,
+			     0, max, 0, def, NULL, 0, 0,
 			     flags, NULL, qmenu_int, ptr_null, NULL);
 }
 EXPORT_SYMBOL(v4l2_ctrl_new_int_menu);
diff --git a/include/media/v4l2-ctrls.h b/include/media/v4l2-ctrls.h
index 59679a42b3e7..c35514c5bf88 100644
--- a/include/media/v4l2-ctrls.h
+++ b/include/media/v4l2-ctrls.h
@@ -211,7 +211,8 @@ typedef void (*v4l2_ctrl_notify_fnc)(struct v4l2_ctrl *ctrl, void *priv);
  *		except for dynamic arrays. In that case it is in the range of
  *		1 to @p_array_alloc_elems.
  * @dims:	The size of each dimension.
- * @nr_of_dims:The number of dimensions in @dims.
+ * @nr_of_dims: The number of dimensions in @dims.
+ * @fraction_bits: The number of fraction bits for fixed point values.
  * @menu_skip_mask: The control's skip mask for menu controls. This makes it
  *		easy to skip menu items that are not valid. If bit X is set,
  *		then menu item X is skipped. Of course, this only works for
@@ -228,6 +229,7 @@ typedef void (*v4l2_ctrl_notify_fnc)(struct v4l2_ctrl *ctrl, void *priv);
  *		:math:`ceil(\frac{maximum - minimum}{step}) + 1`.
  *		Used only if the @type is %V4L2_CTRL_TYPE_INTEGER_MENU.
  * @flags:	The control's flags.
+ * @fraction_bits: The number of fraction bits for fixed point values.
  * @priv:	The control's private pointer. For use by the driver. It is
  *		untouched by the control framework. Note that this pointer is
  *		not freed when the control is deleted. Should this be needed
@@ -286,6 +288,7 @@ struct v4l2_ctrl {
 	u32 new_elems;
 	u32 dims[V4L2_CTRL_MAX_DIMS];
 	u32 nr_of_dims;
+	u32 fraction_bits;
 	union {
 		u64 step;
 		u64 menu_skip_mask;
@@ -426,6 +429,7 @@ struct v4l2_ctrl_handler {
  * @dims:	The size of each dimension.
  * @elem_size:	The size in bytes of the control.
  * @flags:	The control's flags.
+ * @fraction_bits: The number of fraction bits for fixed point values.
  * @menu_skip_mask: The control's skip mask for menu controls. This makes it
  *		easy to skip menu items that are not valid. If bit X is set,
  *		then menu item X is skipped. Of course, this only works for
@@ -455,6 +459,7 @@ struct v4l2_ctrl_config {
 	u32 dims[V4L2_CTRL_MAX_DIMS];
 	u32 elem_size;
 	u32 flags;
+	u32 fraction_bits;
 	u64 menu_skip_mask;
 	const char * const *qmenu;
 	const s64 *qmenu_int;
diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
index c3d4e490ce7c..26ecac19722a 100644
--- a/include/uapi/linux/videodev2.h
+++ b/include/uapi/linux/videodev2.h
@@ -1944,9 +1944,27 @@ struct v4l2_query_ext_ctrl {
 	__u32                elems;
 	__u32                nr_of_dims;
 	__u32                dims[V4L2_CTRL_MAX_DIMS];
-	__u32		     reserved[32];
+	__u32                fraction_bits;
+	__u32		     reserved[31];
 };

+static inline __s64 v4l2_fp_compose(__s64 i, __s64 f, unsigned int fraction_bits)
+{
+	return (i << fraction_bits) + f;
+}
+
+static inline __s64 v4l2_fp_integer(__s64 v, unsigned int fraction_bits)
+{
+	return v / (1LL << fraction_bits);
+}
+
+static inline __s64 v4l2_fp_fraction(__s64 v, unsigned int fraction_bits)
+{
+	__u64 mask = (1ULL << fraction_bits) - 1;
+
+	return v < 0 ? -((-v) & mask) : (v & mask);
+}
+
 /*  Used in the VIDIOC_QUERYMENU ioctl for querying menu items */
 struct v4l2_querymenu {
 	__u32		id;
-- 
2.42.0