Add new ioctls to set and get subdev client capabilities. Client in this
context means the userspace application which opens the subdev device
node.
For now we only add a single flag, V4L2_SUBDEV_CLIENT_CAP_STREAMS, which
indicates that the client is streams-aware.
The reason for needing such a flag is as follows:
Many structs passed via ioctls, e.g. struct v4l2_subdev_format, contain
reserved fields (usually a single array field). These reserved fields
can be used to extend the ioctl. The userspace is required to zero the
reserved fields.
We recently added a new 'stream' field to many of these structs, and the
space for the field was taken from these reserved arrays. The assumption
was that these new 'stream' fields are always initialized to zero if the
userspace does not use them. This was a mistake, as, as mentioned above,
the userspace is required to zero the _reserved_ fields. In other words,
there is no requirement to zero this new stream field, and if the
userspace doesn't use the field (which is the case for all userspace
applications at the moment), the field may contain random data.
This shows that the way the reserved fields are defined in v4l2 is, in
my opinion, somewhat broken, but there is nothing to do about that.
To fix this issue we need a way for the userspace to tell the kernel
that the userspace has indeed set the 'stream' field, and it's fine for
the kernel to access it. This is achieved with the new iotcl, which the
userspace should usually use right after opening the subdev device node.
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@xxxxxxxxxxxxxxxx>
---
.../userspace-api/media/v4l/user-func.rst | 1 +
.../media/v4l/vidioc-subdev-g-client-cap.rst | 56 ++++++++++++++++
drivers/media/v4l2-core/v4l2-subdev.c | 64 ++++++++++++++++++-
include/media/v4l2-subdev.h | 1 +
include/uapi/linux/v4l2-subdev.h | 23 +++++++
5 files changed, 143 insertions(+), 2 deletions(-)
create mode 100644 Documentation/userspace-api/media/v4l/vidioc-subdev-g-client-cap.rst
diff --git a/Documentation/userspace-api/media/v4l/user-func.rst b/Documentation/userspace-api/media/v4l/user-func.rst
index 228c1521f190..15ff0bf7bbe6 100644
--- a/Documentation/userspace-api/media/v4l/user-func.rst
+++ b/Documentation/userspace-api/media/v4l/user-func.rst
@@ -72,6 +72,7 @@ Function Reference
vidioc-subdev-g-frame-interval
vidioc-subdev-g-routing
vidioc-subdev-g-selection
+ vidioc-subdev-g-client-cap
vidioc-subdev-querycap
vidioc-subscribe-event
func-mmap
diff --git a/Documentation/userspace-api/media/v4l/vidioc-subdev-g-client-cap.rst b/Documentation/userspace-api/media/v4l/vidioc-subdev-g-client-cap.rst
new file mode 100644
index 000000000000..d3cfe932bb16
--- /dev/null
+++ b/Documentation/userspace-api/media/v4l/vidioc-subdev-g-client-cap.rst
@@ -0,0 +1,56 @@
+.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
+.. c:namespace:: V4L
+
+.. _VIDIOC_SUBDEV_G_CLIENT_CAP:
+
+************************************************************
+ioctl VIDIOC_SUBDEV_G_CLIENT_CAP, VIDIOC_SUBDEV_S_CLIENT_CAP
+************************************************************
+
+Name
+====
+
+VIDIOC_SUBDEV_G_CLIENT_CAP - VIDIOC_SUBDEV_S_CLIENT_CAP - Get or set client capabilities.
+
+
+Synopsis
+========
+
+.. c:macro:: VIDIOC_SUBDEV_G_CLIENT_CAP
+
+``int ioctl(int fd, VIDIOC_SUBDEV_G_CLIENT_CAP, struct v4l2_subdev_client_capability *argp)``
+
+.. c:macro:: VIDIOC_SUBDEV_S_CLIENT_CAP
+
+``int ioctl(int fd, VIDIOC_SUBDEV_S_CLIENT_CAP, struct v4l2_subdev_client_capability *argp)``
+
+Arguments
+=========
+
+``fd``
+ File descriptor returned by :ref:`open() <func-open>`.
+
+``argp``
+ Pointer to struct :c:type:`v4l2_subdev_client_capability`.
+
+Description
+===========
+
+These ioctls are used to get and set the client capabilities. By default no
+client capabilities are set.
+
+The ``VIDIOC_SUBDEV_S_CLIENT_CAP`` will modify the struct
+:c:type:`v4l2_subdev_client_capability` to reflect the capabilities that were
+accepted. A common case for the kernel not accepting a capability is that the
+kernel is older than the headers the userspace uses, and thus the capability is
+unknown to the kernel.
+
+Return Value
+============
+
+On success 0 is returned, on error -1 and the ``errno`` variable is set
+appropriately. The generic error codes are described at the
+:ref:`Generic Error Codes <gen-errors>` chapter.
+
+ENOIOCTLCMD
+ The kernel does not support this ioctl.
diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
index dff1d9be7841..e741439c6816 100644
--- a/drivers/media/v4l2-core/v4l2-subdev.c
+++ b/drivers/media/v4l2-core/v4l2-subdev.c
@@ -498,8 +498,10 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg,
struct video_device *vdev = video_devdata(file);
struct v4l2_subdev *sd = vdev_to_v4l2_subdev(vdev);
struct v4l2_fh *vfh = file->private_data;
+ struct v4l2_subdev_fh *subdev_fh = to_v4l2_subdev_fh(vfh);
bool ro_subdev = test_bit(V4L2_FL_SUBDEV_RO_DEVNODE, &vdev->flags);
bool streams_subdev = sd->flags & V4L2_SUBDEV_FL_STREAMS;
+ bool client_supports_streams = subdev_fh->client_caps & V4L2_SUBDEV_CLIENT_CAP_STREAMS;
int rval;
switch (cmd) {
@@ -624,6 +626,9 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg,
case VIDIOC_SUBDEV_G_FMT: {
struct v4l2_subdev_format *format = arg;
+ if (!client_supports_streams)
+ format->stream = 0;
+
memset(format->reserved, 0, sizeof(format->reserved));
memset(format->format.reserved, 0, sizeof(format->format.reserved));
return v4l2_subdev_call(sd, pad, get_fmt, state, format);
@@ -635,6 +640,9 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg,
if (format->which != V4L2_SUBDEV_FORMAT_TRY && ro_subdev)
return -EPERM;
+ if (!client_supports_streams)
+ format->stream = 0;
+
memset(format->reserved, 0, sizeof(format->reserved));
memset(format->format.reserved, 0, sizeof(format->format.reserved));
return v4l2_subdev_call(sd, pad, set_fmt, state, format);
@@ -644,6 +652,9 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg,
struct v4l2_subdev_crop *crop = arg;
struct v4l2_subdev_selection sel;
+ if (!client_supports_streams)
+ crop->stream = 0;
+
memset(crop->reserved, 0, sizeof(crop->reserved));
memset(&sel, 0, sizeof(sel));
sel.which = crop->which;
@@ -665,6 +676,9 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg,
if (crop->which != V4L2_SUBDEV_FORMAT_TRY && ro_subdev)
return -EPERM;
+ if (!client_supports_streams)
+ crop->stream = 0;
+
memset(crop->reserved, 0, sizeof(crop->reserved));
memset(&sel, 0, sizeof(sel));
sel.which = crop->which;
@@ -683,6 +697,9 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg,
case VIDIOC_SUBDEV_ENUM_MBUS_CODE: {
struct v4l2_subdev_mbus_code_enum *code = arg;
+ if (!client_supports_streams)
+ code->stream = 0;
+
memset(code->reserved, 0, sizeof(code->reserved));
return v4l2_subdev_call(sd, pad, enum_mbus_code, state,
code);
@@ -691,6 +708,9 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg,
case VIDIOC_SUBDEV_ENUM_FRAME_SIZE: {
struct v4l2_subdev_frame_size_enum *fse = arg;
+ if (!client_supports_streams)
+ fse->stream = 0;
+
memset(fse->reserved, 0, sizeof(fse->reserved));
return v4l2_subdev_call(sd, pad, enum_frame_size, state,
fse);
@@ -699,6 +719,9 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg,
case VIDIOC_SUBDEV_G_FRAME_INTERVAL: {
struct v4l2_subdev_frame_interval *fi = arg;
+ if (!client_supports_streams)
+ fi->stream = 0;
+
memset(fi->reserved, 0, sizeof(fi->reserved));
return v4l2_subdev_call(sd, video, g_frame_interval, arg);
}
@@ -709,6 +732,9 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg,
if (ro_subdev)
return -EPERM;
+ if (!client_supports_streams)
+ fi->stream = 0;
+
memset(fi->reserved, 0, sizeof(fi->reserved));
return v4l2_subdev_call(sd, video, s_frame_interval, arg);
}
@@ -716,6 +742,9 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg,
case VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL: {
struct v4l2_subdev_frame_interval_enum *fie = arg;
+ if (!client_supports_streams)
+ fie->stream = 0;
+
memset(fie->reserved, 0, sizeof(fie->reserved));
return v4l2_subdev_call(sd, pad, enum_frame_interval, state,
fie);
@@ -724,6 +753,9 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg,
case VIDIOC_SUBDEV_G_SELECTION: {
struct v4l2_subdev_selection *sel = arg;
+ if (!client_supports_streams)
+ sel->stream = 0;
+
memset(sel->reserved, 0, sizeof(sel->reserved));
return v4l2_subdev_call(
sd, pad, get_selection, state, sel);
@@ -735,6 +767,9 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg,
if (sel->which != V4L2_SUBDEV_FORMAT_TRY && ro_subdev)
return -EPERM;
+ if (!client_supports_streams)
+ sel->stream = 0;
+
memset(sel->reserved, 0, sizeof(sel->reserved));
return v4l2_subdev_call(
sd, pad, set_selection, state, sel);
@@ -805,7 +840,7 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg,
struct v4l2_subdev_routing *routing = arg;
struct v4l2_subdev_krouting *krouting;
- if (!v4l2_subdev_enable_streams_api)
+ if (!client_supports_streams)
return -ENOIOCTLCMD;
if (!(sd->flags & V4L2_SUBDEV_FL_STREAMS))
@@ -835,7 +870,7 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg,
struct v4l2_subdev_krouting krouting = {};
unsigned int i;
- if (!v4l2_subdev_enable_streams_api)
+ if (!client_supports_streams)
return -ENOIOCTLCMD;
if (!(sd->flags & V4L2_SUBDEV_FL_STREAMS))
@@ -876,6 +911,31 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg,
routing->which, &krouting);
}
+ case VIDIOC_SUBDEV_G_CLIENT_CAP: {
+ struct v4l2_subdev_client_capability *client_cap = arg;
+
+ if (!v4l2_subdev_enable_streams_api)
+ return -ENOIOCTLCMD;
+
+ client_cap->capabilities = subdev_fh->client_caps;
+
+ return 0;
+ }
+
+ case VIDIOC_SUBDEV_S_CLIENT_CAP: {
+ struct v4l2_subdev_client_capability *client_cap = arg;
+
+ if (!v4l2_subdev_enable_streams_api)
+ return -ENOIOCTLCMD;
+
+ /* Filter out unsupported capabilities */
+ client_cap->capabilities &= V4L2_SUBDEV_CLIENT_CAP_STREAMS;
+
+ subdev_fh->client_caps = client_cap->capabilities;
+
+ return 0;
+ }
+
default:
return v4l2_subdev_call(sd, core, ioctl, cmd, arg);
}
diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
index 17773be4a4ee..b5bb5b802929 100644
--- a/include/media/v4l2-subdev.h
+++ b/include/media/v4l2-subdev.h
@@ -1121,6 +1121,7 @@ struct v4l2_subdev_fh {
struct module *owner;
#if defined(CONFIG_VIDEO_V4L2_SUBDEV_API)
struct v4l2_subdev_state *state;
+ u64 client_caps;
#endif
};
diff --git a/include/uapi/linux/v4l2-subdev.h b/include/uapi/linux/v4l2-subdev.h
index 654d659de835..9f863240a458 100644
--- a/include/uapi/linux/v4l2-subdev.h
+++ b/include/uapi/linux/v4l2-subdev.h
@@ -233,6 +233,26 @@ struct v4l2_subdev_routing {
__u32 reserved[6];
};
+/*
+ * The client is aware of streams. Setting this flag enables the use of streams
+ * and routing related ioctls and fields. If this is not set (which is the
+ * default), all the 'stream' fields referring to the stream number will be
+ * forced to 0 by the kernel, and routing related ioctls will return
+ * -ENOIOCTLCMD.
+ */
+ #define V4L2_SUBDEV_CLIENT_CAP_STREAMS (1U << 0)
+
+/**
+ * struct v4l2_subdev_client_capability - Capabilities of the client accessing the subdev
+ *
+ * @capabilities: A bitmask of V4L2_SUBDEV_CLIENT_CAP_* flags.
+ * @reserved: drivers and applications must zero this array
+ */
+struct v4l2_subdev_client_capability {
+ __u64 capabilities;
+ __u32 reserved[6];
+};
+
/* Backwards compatibility define --- to be removed */
#define v4l2_subdev_edid v4l2_edid
@@ -250,6 +270,9 @@ struct v4l2_subdev_routing {
#define VIDIOC_SUBDEV_S_SELECTION _IOWR('V', 62, struct v4l2_subdev_selection)
#define VIDIOC_SUBDEV_G_ROUTING _IOWR('V', 38, struct v4l2_subdev_routing)
#define VIDIOC_SUBDEV_S_ROUTING _IOWR('V', 39, struct v4l2_subdev_routing)
+#define VIDIOC_SUBDEV_G_CLIENT_CAP _IOR('V', 101, struct v4l2_subdev_client_capability)
+#define VIDIOC_SUBDEV_S_CLIENT_CAP _IOWR('V', 102, struct v4l2_subdev_client_capability)
+
/* The following ioctls are identical to the ioctls in videodev2.h */
#define VIDIOC_SUBDEV_G_STD _IOR('V', 23, v4l2_std_id)
#define VIDIOC_SUBDEV_S_STD _IOW('V', 24, v4l2_std_id)
--
2.34.1
