I am trying to interact with devices using the V4L2 API. The API defines
the following struct
typedef __u64 v4l2_std_id
struct v4l2_input {
__u32 index;
__u8 name[32];
__u32 type;
__u32 audioset;
__u32 tuner;
v4l2_std_id std;
__u32 status;
__u32 capabilities;
__u32 reserved[3];
};
In Go I have replicated this struct with the following
type StandardId uint64
type Input struct {
Index uint32
Name [32]uint8
Type uint32
Audioset uint32
Tuner uint32
Standard StandardId
Status uint32
Capabilities uint32
reserved [3]uint32
}
When I attempt to use the Go struct in an Ioctl call I get the following
error
EnumerateVideoInput: inappropriate ioctl for device
>
I have managed to track this down to what appears to be a slight difference
in the size of the structs.
The Go struct has sizeof 76 bytes and the C struct has sizeof 80 bytes.
This means the creation of my ioctl request value is incorrect as I
generate a value of 3,226,228,250 and the actual C #define from
linux/videodev2.h has value 3,226,490,394.
Up to this point I have not had a problem replicating the C structs in Go
and using them to call Ioctl, with calls succeeding and all fields being
populated with the expected values so far. It seems that the system calls
in Go do not come with much documentation and I have seen a similar method
to this used elsewhere online hence my adoption of this approach.
My main goal was to avoid having to use CGO as this obviously comes with
overhead on compilation time, etc.
Assuming I haven't missed something glaringly obvious, is it possible to
replicate the C structs in Go and use them in this way?
What would be the recommended approach for using Ioctl?
Does anyone know of some good resources for using the /x/sys/unix package
(specifically Syscall related)?
Thanks
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