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pylibfdt: Support the sequential-write interface

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It is useful to be able to create a device tree from scratch using
software. This is supported in libfdt but not currently available in the
Python bindings.

Add a new FdtSw class to handle this, with various methods corresponding
to the libfdt functions. When the tree is complete, calling AsFdt() will
return the completed device-tree object.

Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
This commit is contained in:
Simon Glass 2018-07-10 14:49:07 -06:00 committed by David Gibson
parent 9b0e4fe260
commit 853649acce
2 changed files with 497 additions and 82 deletions
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460
pylibfdt/libfdt.i
View file

@ -57,6 +57,18 @@
%{
#define SWIG_FILE_WITH_INIT
#include "libfdt.h"
/*
* We rename this function here to avoid problems with swig, since we also have
* a struct called fdt_property. That struct causes swig to create a class in
* libfdt.py called fdt_property(), which confuses things.
*/
static int fdt_property_stub(void *fdt, const char *name, const char *val,
int len)
{
return fdt_property(fdt, name, val, len);
}
%}
%pythoncode %{
@ -88,6 +100,7 @@ import struct
# Pass this as the 'quiet' parameter to return -ENOTFOUND on NOTFOUND errors,
# instead of raising an exception.
QUIET_NOTFOUND = (NOTFOUND,)
QUIET_NOSPACE = (NOSPACE,)
class FdtException(Exception):
@ -153,22 +166,18 @@ def check_err_null(val, quiet=()):
raise FdtException(val)
return val
class Fdt:
"""Device tree class, supporting all operations
class FdtRo(object):
"""Class for a read-only device-tree
The Fdt object is created is created from a device tree binary file,
e.g. with something like:
This is a base class used by FdtRw (read-write access) and FdtSw
(sequential-write access). It implements read-only access to the
device tree.
fdt = Fdt(open("filename.dtb").read())
Here are the three classes and when you should use them:
Operations can then be performed using the methods in this class. Each
method xxx(args...) corresponds to a libfdt function fdt_xxx(fdt, args...).
All methods raise an FdtException if an error occurs. To avoid this
behaviour a 'quiet' parameter is provided for some functions. This
defaults to empty, but you can pass a list of errors that you expect.
If one of these errors occurs, the function will return an error number
(e.g. -NOTFOUND).
FdtRo - read-only access to an existing FDT
FdtRw - read-write access to an existing FDT (most common case)
FdtSw - for creating a new FDT, as well as allowing read-only access
"""
def __init__(self, data):
self._fdt = bytearray(data)
@ -433,6 +442,91 @@ class Fdt:
return pdata
return Property(pdata[0], pdata[1])
def getprop(self, nodeoffset, prop_name, quiet=()):
"""Get a property from a node
Args:
nodeoffset: Node offset containing property to get
prop_name: Name of property to get
quiet: Errors to ignore (empty to raise on all errors)
Returns:
Value of property as a Property object (which can be used as a
bytearray/string), or -ve error number. On failure, returns an
integer error
Raises:
FdtError if any error occurs (e.g. the property is not found)
"""
pdata = check_err_null(fdt_getprop(self._fdt, nodeoffset, prop_name),
quiet)
if isinstance(pdata, (int)):
return pdata
return Property(prop_name, bytearray(pdata[0]))
def get_phandle(self, nodeoffset):
"""Get the phandle of a node
Args:
nodeoffset: Node offset to check
Returns:
phandle of node, or 0 if the node has no phandle or another error
occurs
"""
return fdt_get_phandle(self._fdt, nodeoffset)
def parent_offset(self, nodeoffset, quiet=()):
"""Get the offset of a node's parent
Args:
nodeoffset: Node offset to check
quiet: Errors to ignore (empty to raise on all errors)
Returns:
The offset of the parent node, if any
Raises:
FdtException if no parent found or other error occurs
"""
return check_err(fdt_parent_offset(self._fdt, nodeoffset), quiet)
def node_offset_by_phandle(self, phandle, quiet=()):
"""Get the offset of a node with the given phandle
Args:
phandle: Phandle to search for
quiet: Errors to ignore (empty to raise on all errors)
Returns:
The offset of node with that phandle, if any
Raises:
FdtException if no node found or other error occurs
"""
return check_err(fdt_node_offset_by_phandle(self._fdt, phandle), quiet)
class Fdt(FdtRo):
"""Device tree class, supporting all operations
The Fdt object is created is created from a device tree binary file,
e.g. with something like:
fdt = Fdt(open("filename.dtb").read())
Operations can then be performed using the methods in this class. Each
method xxx(args...) corresponds to a libfdt function fdt_xxx(fdt, args...).
All methods raise an FdtException if an error occurs. To avoid this
behaviour a 'quiet' parameter is provided for some functions. This
defaults to empty, but you can pass a list of errors that you expect.
If one of these errors occurs, the function will return an error number
(e.g. -NOTFOUND).
"""
def __init__(self, data):
FdtRo.__init__(self, data)
@staticmethod
def create_empty_tree(size, quiet=()):
"""Create an empty device tree ready for use
@ -486,55 +580,6 @@ class Fdt:
del self._fdt[self.totalsize():]
return err
def getprop(self, nodeoffset, prop_name, quiet=()):
"""Get a property from a node
Args:
nodeoffset: Node offset containing property to get
prop_name: Name of property to get
quiet: Errors to ignore (empty to raise on all errors)
Returns:
Value of property as a Property object (which can be used as a
bytearray/string), or -ve error number. On failure, returns an
integer error
Raises:
FdtError if any error occurs (e.g. the property is not found)
"""
pdata = check_err_null(fdt_getprop(self._fdt, nodeoffset, prop_name),
quiet)
if isinstance(pdata, (int)):
return pdata
return Property(prop_name, bytearray(pdata[0]))
def get_phandle(self, nodeoffset):
"""Get the phandle of a node
Args:
nodeoffset: Node offset to check
Returns:
phandle of node, or 0 if the node has no phandle or another error
occurs
"""
return fdt_get_phandle(self._fdt, nodeoffset)
def parent_offset(self, nodeoffset, quiet=()):
"""Get the offset of a node's parent
Args:
nodeoffset: Node offset to check
quiet: Errors to ignore (empty to raise on all errors)
Returns:
The offset of the parent node, if any
Raises:
FdtException if no parent found or other error occurs
"""
return check_err(fdt_parent_offset(self._fdt, nodeoffset), quiet)
def set_name(self, nodeoffset, name, quiet=()):
"""Set the name of a node
@ -640,21 +685,6 @@ class Fdt:
"""
return check_err(fdt_delprop(self._fdt, nodeoffset, prop_name))
def node_offset_by_phandle(self, phandle, quiet=()):
"""Get the offset of a node with the given phandle
Args:
phandle: Phandle to search for
quiet: Errors to ignore (empty to raise on all errors)
Returns:
The offset of node with that phandle, if any
Raises:
FdtException if no node found or other error occurs
"""
return check_err(fdt_node_offset_by_phandle(self._fdt, phandle), quiet)
class Property(bytearray):
"""Holds a device tree property name and value.
@ -693,6 +723,268 @@ class Property(bytearray):
if 0 in self[:-1]:
raise ValueError('Property contains embedded nul characters')
return self[:-1].decode('utf-8')
class FdtSw(FdtRo):
"""Software interface to create a device tree from scratch
The methods in this class work by adding to an existing 'partial' device
tree buffer of a fixed size created by instantiating this class. When the
tree is complete, call as_fdt() to obtain a device tree ready to be used.
Similarly with nodes, a new node is started with begin_node() and finished
with end_node().
The context manager functions can be used to make this a bit easier:
# First create the device tree with a node and property:
sw = FdtSw()
with sw.add_node('node'):
sw.property_u32('reg', 2)
fdt = sw.as_fdt()
# Now we can use it as a real device tree
fdt.setprop_u32(0, 'reg', 3)
The size hint provides a starting size for the space to be used by the
device tree. This will be increased automatically as needed as new items
are added to the tree.
"""
INC_SIZE = 1024 # Expand size by this much when out of space
def __init__(self, size_hint=None):
"""Create a new FdtSw object
Args:
size_hint: A hint as to the initial size to use
Raises:
ValueError if size_hint is negative
Returns:
FdtSw object on success, else integer error code (if not raising)
"""
if not size_hint:
size_hint = self.INC_SIZE
fdtsw = bytearray(size_hint)
err = check_err(fdt_create(fdtsw, size_hint))
if err:
return err
self._fdt = fdtsw
def as_fdt(self):
"""Convert a FdtSw into an Fdt so it can be accessed as normal
Creates a new Fdt object from the work-in-progress device tree. This
does not call fdt_finish() on the current object, so it is possible to
add more nodes/properties and call as_fdt() again to get an updated
tree.
Returns:
Fdt object allowing access to the newly created device tree
"""
fdtsw = bytearray(self._fdt)
check_err(fdt_finish(fdtsw))
return Fdt(fdtsw)
def check_space(self, val):
"""Check if we need to add more space to the FDT
This should be called with the error code from an operation. If this is
-NOSPACE then the FDT will be expanded to have more space, and True will
be returned, indicating that the operation needs to be tried again.
Args:
val: Return value from the operation that was attempted
Returns:
True if the operation must be retried, else False
"""
if check_err(val, QUIET_NOSPACE) < 0:
self.resize(len(self._fdt) + self.INC_SIZE)
return True
return False
def resize(self, size):
"""Resize the buffer to accommodate a larger tree
Args:
size: New size of tree
Raises:
FdtException on any error
"""
fdt = bytearray(size)
err = check_err(fdt_resize(self._fdt, fdt, size))
self._fdt = fdt
def add_reservemap_entry(self, addr, size):
"""Add a new memory reserve map entry
Once finished adding, you must call finish_reservemap().
Args:
addr: 64-bit start address
size: 64-bit size
Raises:
FdtException on any error
"""
while self.check_space(fdt_add_reservemap_entry(self._fdt, addr,
size)):
pass
def finish_reservemap(self):
"""Indicate that there are no more reserve map entries to add
Raises:
FdtException on any error
"""
while self.check_space(fdt_finish_reservemap(self._fdt)):
pass
def begin_node(self, name):
"""Begin a new node
Use this before adding properties to the node. Then call end_node() to
finish it. You can also use the context manager as shown in the FdtSw
class comment.
Args:
name: Name of node to begin
Raises:
FdtException on any error
"""
while self.check_space(fdt_begin_node(self._fdt, name)):
pass
def property_string(self, name, string):
"""Add a property with a string value
The string will be nul-terminated when written to the device tree
Args:
name: Name of property to add
string: String value of property
Raises:
FdtException on any error
"""
while self.check_space(fdt_property_string(self._fdt, name, string)):
pass
def property_u32(self, name, val):
"""Add a property with a 32-bit value
Write a single-cell value to the device tree
Args:
name: Name of property to add
val: Value of property
Raises:
FdtException on any error
"""
while self.check_space(fdt_property_u32(self._fdt, name, val)):
pass
def property_u64(self, name, val):
"""Add a property with a 64-bit value
Write a double-cell value to the device tree in big-endian format
Args:
name: Name of property to add
val: Value of property
Raises:
FdtException on any error
"""
while self.check_space(fdt_property_u64(self._fdt, name, val)):
pass
def property_cell(self, name, val):
"""Add a property with a single-cell value
Write a single-cell value to the device tree
Args:
name: Name of property to add
val: Value of property
quiet: Errors to ignore (empty to raise on all errors)
Raises:
FdtException on any error
"""
while self.check_space(fdt_property_cell(self._fdt, name, val)):
pass
def property(self, name, val):
"""Add a property
Write a new property with the given value to the device tree. The value
is taken as is and is not nul-terminated
Args:
name: Name of property to add
val: Value of property
quiet: Errors to ignore (empty to raise on all errors)
Raises:
FdtException on any error
"""
while self.check_space(fdt_property_stub(self._fdt, name, val,
len(val))):
pass
def end_node(self):
"""End a node
Use this after adding properties to a node to close it off. You can also
use the context manager as shown in the FdtSw class comment.
Args:
quiet: Errors to ignore (empty to raise on all errors)
Raises:
FdtException on any error
"""
while self.check_space(fdt_end_node(self._fdt)):
pass
def add_node(self, name):
"""Create a new context for adding a node
When used in a 'with' clause this starts a new node and finishes it
afterward.
Args:
name: Name of node to add
"""
return NodeAdder(self, name)
class NodeAdder():
"""Class to provide a node context
This allows you to add nodes in a more natural way:
with fdtsw.add_node('name'):
fdtsw.property_string('test', 'value')
The node is automatically completed with a call to end_node() when the
context exits.
"""
def __init__(self, fdtsw, name):
self._fdt = fdtsw
self._name = name
def __enter__(self):
self._fdt.begin_node(self._name)
def __exit__(self, type, value, traceback):
self._fdt.end_node()
%}
%rename(fdt_property) fdt_property_func;
@ -757,6 +1049,11 @@ typedef uint32_t fdt32_t;
$1 = PyString_AsString($input); /* char *str */
}
/* typemap used for fdt_add_reservemap_entry() */
%typemap(in) uint64_t {
$1 = PyLong_AsUnsignedLong($input);
}
/* typemaps used for fdt_next_node() */
%typemap(in, numinputs=1) int *depth (int depth) {
depth = (int) PyInt_AsLong($input);
@ -800,4 +1097,13 @@ uint32_t fdt_boot_cpuid_phys(const void *fdt);
uint32_t fdt_size_dt_strings(const void *fdt);
uint32_t fdt_size_dt_struct(const void *fdt);
int fdt_property_string(void *fdt, const char *name, const char *val);
int fdt_property_cell(void *fdt, const char *name, uint32_t val);
/*
* This function has a stub since the name fdt_property is used for both a
* function and a struct, which confuses SWIG.
*/
int fdt_property_stub(void *fdt, const char *name, const char *val, int len);
%include <../libfdt/libfdt.h>

119
tests/pylibfdt_tests.py
View file

@ -56,17 +56,32 @@ import unittest
sys.path.insert(0, '../pylibfdt')
import libfdt
from libfdt import Fdt, FdtException, QUIET_NOTFOUND, QUIET_ALL
from libfdt import Fdt, FdtSw, FdtException, QUIET_NOTFOUND, QUIET_ALL
small_size = 160
full_size = 1024
TEST_ADDR_1H = 0xdeadbeef
TEST_ADDR_1L = 0x00000000
TEST_ADDR_1 = (TEST_ADDR_1H << 32) | TEST_ADDR_1L
TEST_ADDR_1 = 0x8000000000000000
TEST_SIZE_1H = 0x00000000
TEST_SIZE_1L = 0x00100000
TEST_SIZE_1 = (TEST_SIZE_1H << 32) | TEST_SIZE_1L
TEST_ADDR_2H = 0
TEST_ADDR_2L = 123456789
TEST_ADDR_2 = (TEST_ADDR_2H << 32) | TEST_ADDR_2L
TEST_SIZE_2H = 0
TEST_SIZE_2L = 010000
TEST_SIZE_2 = (TEST_SIZE_2H << 32) | TEST_SIZE_2L
TEST_VALUE_1 = 0xdeadbeef
TEST_VALUE_2 = 123456789
TEST_VALUE64_1H = 0xdeadbeef
TEST_VALUE64_1L = 0x01abcdef
TEST_VALUE64_1 = (TEST_VALUE64_1H << 32) | TEST_VALUE64_1L
PHANDLE_1 = 0x2000
PHANDLE_2 = 0x2001
TEST_STRING_1 = 'hello world'
TEST_STRING_2 = 'hi world'
TEST_STRING_3 = u'unicode ' + unichr(467)
@ -94,8 +109,8 @@ def _ReadFdt(fname):
"""
return libfdt.Fdt(open(fname).read())
class PyLibfdtTests(unittest.TestCase):
"""Test class for pylibfdt
class PyLibfdtBasicTests(unittest.TestCase):
"""Test class for basic pylibfdt access functions
Properties:
fdt: Device tree file used for testing
@ -481,5 +496,99 @@ class PyLibfdtTests(unittest.TestCase):
self.assertIn('embedded nul', str(e.exception))
class PyLibfdtSwTests(unittest.TestCase):
"""Test class for pylibfdt sequential-write DT creation
"""
def assertOk(self, err_code):
self.assertEquals(0, err_code)
def testCreate(self):
# First check the minimum size and also the FdtSw() constructor
with self.assertRaisesRegexp(FdtException, get_err(libfdt.NOSPACE)):
self.assertEquals(-libfdt.NOSPACE, FdtSw(3))
sw = FdtSw()
sw.add_reservemap_entry(TEST_ADDR_1, TEST_SIZE_1)
sw.add_reservemap_entry(TEST_ADDR_2, TEST_SIZE_2)
sw.finish_reservemap()
sw.begin_node('')
sw.property_string('compatible', 'test_tree1')
sw.property_u32('prop-int', TEST_VALUE_1)
sw.property_u32('prop-int', TEST_VALUE_1)
sw.property_u64('prop-int64', TEST_VALUE64_1)
sw.property_string('prop-str', TEST_STRING_1)
sw.property_u32('#address-cells', 1)
sw.property_u32('#size-cells', 0)
sw.begin_node('subnode@1')
sw.property_string('compatible', 'subnode1')
sw.property_u32('reg', 1)
sw.property_cell('prop-int', TEST_VALUE_1)
sw.begin_node('subsubnode')
sw.property('compatible', 'subsubnode1\0subsubnode')
sw.property_cell('prop-int', TEST_VALUE_1)
sw.end_node()
sw.begin_node('ss1')
sw.end_node()
sw.end_node()
for i in range(2, 11):
with sw.add_node('subnode@%d' % i):
sw.property_u32('reg', 2)
sw.property_cell('linux,phandle', PHANDLE_1)
sw.property_cell('prop-int', TEST_VALUE_2)
sw.property_u32('#address-cells', 1)
sw.property_u32('#size-cells', 0)
with sw.add_node('subsubnode@0'):
sw.property_u32('reg', 0)
sw.property_cell('phandle', PHANDLE_2)
sw.property('compatible', 'subsubnode2\0subsubnode')
sw.property_cell('prop-int', TEST_VALUE_2)
with sw.add_node('ss2'):
pass
sw.end_node()
fdt = sw.as_fdt()
self.assertEqual(2, fdt.num_mem_rsv())
self.assertEqual([TEST_ADDR_1, TEST_SIZE_1], fdt.get_mem_rsv(0))
# Make sure we can add a few more things
with sw.add_node('another'):
sw.property_u32('reg', 3)
# Make sure we can read from the tree too
node = sw.path_offset('/subnode@1')
self.assertEqual('subnode1' + chr(0), sw.getprop(node, 'compatible'))
# Make sure we did at least two resizes
self.assertTrue(len(fdt.as_bytearray()) > FdtSw.INC_SIZE * 2)
class PyLibfdtRoTests(unittest.TestCase):
"""Test class for read-only pylibfdt access functions
This just tests a few simple cases. Most of the tests are in
PyLibfdtBasicTests.
Properties:
fdt: Device tree file used for testing
"""
def setUp(self):
"""Read in the device tree we use for testing"""
self.fdt = libfdt.FdtRo(open('test_tree1.dtb').read())
def testAccess(self):
"""Basic sanity check for the FdtRo class"""
node = self.fdt.path_offset('/subnode@1')
self.assertEqual('subnode1' + chr(0),
self.fdt.getprop(node, 'compatible'))
node = self.fdt.first_subnode(node)
self.assertEqual('this is a placeholder string\0string2\0',
self.fdt.getprop(node, 'placeholder'))
if __name__ == "__main__":
unittest.main()