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media: v4l2- mediabus: Add usage note for V4L2_MBUS_*

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With the removal of the legacy g_mbus_config and s_mbus_config video
operations, the sole users of V4L2_MBUS_* flags are now the newly
introduced get_mbus_config and set_mbus_config pad operations.

As the semantic of the new operations differs from the semantic of
the legacy ones, add a usage note in the v4l2-mediabus.h header to
specify how to use the flags.

Also add a TODO note to record that we intend to replace the existing
flags with fields, to prevent users from mixing conflicting values
in a single operation call.

Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
This commit is contained in:
Jacopo Mondi 2020-07-17 16:53:20 +02:00 committed by Mauro Carvalho Chehab
parent d9857a6d81
commit ddf5c927bd
1 changed files with 29 additions and 4 deletions
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33
include/media/v4l2-mediabus.h
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@ -11,9 +11,34 @@
#include <linux/v4l2-mediabus.h>
#include <linux/bitops.h>
/*
* How to use the V4L2_MBUS_* flags:
* Flags are defined for each of the possible states and values of a media
* bus configuration parameter. One and only one bit of each group of flags
* shall be set by the users of the v4l2_subdev_pad_ops.get_mbus_config and
* v4l2_subdev_pad_ops.set_mbus_config operations to ensure that no
* conflicting settings are specified when reporting and setting the media bus
* configuration with the two operations respectively. For example, it is
* invalid to set or clear both the V4L2_MBUS_HSYNC_ACTIVE_HIGH and the
* V4L2_MBUS_HSYNC_ACTIVE_LOW flag at the same time. Instead either flag
* V4L2_MBUS_HSYNC_ACTIVE_HIGH or flag V4L2_MBUS_HSYNC_ACTIVE_LOW shall be
* set. The same is true for the V4L2_MBUS_CSI2_1/2/3/4_LANE flags group: only
* one of these four bits shall be set.
*
* TODO: replace the existing V4L2_MBUS_* flags with structures of fields
* to avoid conflicting settings.
*
* In example:
* #define V4L2_MBUS_HSYNC_ACTIVE_HIGH BIT(2)
* #define V4L2_MBUS_HSYNC_ACTIVE_LOW BIT(3)
* will be replaced by a field whose value reports the intended active state of
* the signal:
* unsigned int v4l2_mbus_hsync_active : 1;
*/
/* Parallel flags */
/*
* Can the client run in master or in slave mode. By "Master mode" an operation
* The client runs in master or in slave mode. By "Master mode" an operation
* mode is meant, when the client (e.g., a camera sensor) is producing
* horizontal and vertical synchronisation. In "Slave mode" the host is
* providing these signals to the slave.
@ -45,17 +70,17 @@
#define V4L2_MBUS_DATA_ENABLE_LOW BIT(15)
/* Serial flags */
/* How many lanes the client can use */
/* CSI-2 D-PHY number of data lanes. */
#define V4L2_MBUS_CSI2_1_LANE BIT(0)
#define V4L2_MBUS_CSI2_2_LANE BIT(1)
#define V4L2_MBUS_CSI2_3_LANE BIT(2)
#define V4L2_MBUS_CSI2_4_LANE BIT(3)
/* On which channels it can send video data */
/* CSI-2 Virtual Channel identifiers. */
#define V4L2_MBUS_CSI2_CHANNEL_0 BIT(4)
#define V4L2_MBUS_CSI2_CHANNEL_1 BIT(5)
#define V4L2_MBUS_CSI2_CHANNEL_2 BIT(6)
#define V4L2_MBUS_CSI2_CHANNEL_3 BIT(7)
/* Does it support only continuous or also non-continuous clock mode */
/* Clock non-continuous mode support. */
#define V4L2_MBUS_CSI2_CONTINUOUS_CLOCK BIT(8)
#define V4L2_MBUS_CSI2_NONCONTINUOUS_CLOCK BIT(9)