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freebsd/share/man/man9/device_get_property.9
Kornel Duleba b344de4d0d Extend device_get_property API
In order to support various types of data stored in device
tree properties or ACPI _DSD packages, create a new enum so
the caller can specify the expected type of a property they
want to read, according to the binding. The bus logic will use
that information to process the underlying data.

For example in DT all integer properties are stored in BE format.
In order to get constant results across different platforms we
need to convert its endianness to match the host.

Another example are ACPI_TYPE_INTEGER properties stored
as uint64_t. Before this patch the ACPI logic would refuse
to read them if the provided buffer was smaller than 8 bytes.
Now this can be handled by using DEVICE_PROP_UINT32 type.

Modify the existing consumers of this API to reflect the changes
and update the man pages accordingly.

Reviewed by: mw
Obtained from: Semihalf
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D33457
2022-03-10 12:11:32 +01:00

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.Dd February 18, 2022
.Dt DEVICE_GET_PROPERTY 9
.Os
.Sh NAME
.Nm device_get_property ,
.Nm device_has_property
.Nd access device specific data
.Sh SYNOPSIS
.In sys/param.h
.In sys/bus.h
.Ft ssize_t
.Fn device_get_property "device_t dev" "const char *prop" "void *val" "size_t sz" \
"device_property_type_t type"
.Ft bool
.Fn device_has_property "device_t dev" "const char *prop"
.Sh DESCRIPTION
Access device specific data provided by the parent bus.
Drivers can use these properties to obtain device capabilities and set
necessary quirks.
.Pp
The underlying property type is specified with the
.Fa type
argument.
Currently the following types are supported:
.Bl -tag -width ".Dv DEVICE_PROP_BUFFER"
.It Dv DEVICE_PROP_BUFFER
The underlying property is a string of bytes.
.It Dv DEVICE_PROP_ANY
Wildcard property type.
.It Dv DEVICE_PROP_UINT32
The underlying property is an array of unsigned 32 bit integers.
The
.Fa sz
argument shall be a multiple of 4.
.It Dv DEVICE_PROP_UINT64
The underlying property is an array of unsigned 64 bit integers.
The
.Fa sz
argument shall be a multiple of 8.
.El
.Sh NOTES
You can pass NULL as pointer to property's value when calling
.Fn device_get_property
to obtain its size.
.Pp
Currently this interface is implemented by
.Xr simplebus 4
and
.Xr acpi 4 .
.Sh RETURN VALUES
.Fn device_get_property
if successful returns property's size, otherwise returns -1.
.Pp
.Fn device_has_property
returns true if given property was found.
.Sh SEE ALSO
.Xr acpi 4 ,
.Xr simplebus 4 ,
.Xr device 9
.Sh AUTHORS
This manual page was written by
.An Bartlomiej Grzesik .