[RFC PATCH v2 1/8] dtoc: openssl: Add GetHexOctet method

[Manorit Chawdhry]

Hi Simon,

On 19:17-20231001, Simon Glass wrote:
> Hi Manorit,
> 
> On Tue, 26 Sept 2023 at 01:58, Manorit Chawdhry <m-chawdhry at ti.com> wrote:
> >
> > HexOctet format is used by openssl for FORMAT:HEX,OCT property in x509
> > certificates. Add a helper function to extract the integer numbers in
> > HEX,OCT format to pass to openssl directly.
> >
> > Signed-off-by: Manorit Chawdhry <m-chawdhry at ti.com>
> > ---
> >  tools/dtoc/fdt_util.py | 20 ++++++++++++++++++++
> >  1 file changed, 20 insertions(+)
> >
> > diff --git a/tools/dtoc/fdt_util.py b/tools/dtoc/fdt_util.py
> > index f1f70568cfef..d51dbf5633d0 100644
> > --- a/tools/dtoc/fdt_util.py
> > +++ b/tools/dtoc/fdt_util.py
> > @@ -100,6 +100,26 @@ def EnsureCompiled(fname, tmpdir=None, capture_stderr=False):
> >      command.run(dtc, *args, capture_stderr=capture_stderr)
> >      return dtb_output
> >
> > +def GetHexOctet(node, propname, default=None):
> 
> What is a hex octet?
> 

It is actually a Hex number in Octet form, basically using 0x0a instead
of 0xa type of thing. 

OpenSSL has complained when we use FORMAT:HEX,OCT:0 type of string
instead of FORMAT:HEX,OCT:00. Tbvh I still haven't been able to find a
clear documentation for this but this is what I have been able to figure
out based on my tests.

> > +    """Get an integer from a property in hex octet form required by openssl
> > +
> 
> You should mention what size property is permitted.
> 
> > +    Args:
> > +        node: Node object to read from
> > +        propname: property name to read
> > +        default: Default value to use if the node/property do not exist
> > +
> > +    Returns:
> > +        Integer value read as a String in Hex Octet Form
> > +    """
> > +    prop = node.props.get(propname)
> > +    if not isinstance(prop.value, list) or len(prop.value) != 2:
> > +        value = GetInt(node, propname)
> > +    elif isinstance(prop.value, list) and len(prop.value) == 2:
> > +        value = GetInt64(node, propname)
> 
> What if it is neither of those?
> 
> > +
> > +    hex_value = '%x' % (value)
> > +    return ('0' * (len(hex_value) & 1)) + hex_value
> 
> Can you do:
> 
> return f'{value:02x}'
> 

With the following suggestion I don't think I need the patch at all
anymore given that no one else seems to be requiring this HEX,OCT just
yet and am still in the process of finding a clear documentation for it.

Will be dropping that patch after testing if not required to be generic.
Thanks!

Regards,
Manorit

> ?
> 
> 
> > +
> >  def GetInt(node, propname, default=None):
> >      """Get an integer from a property
> >
> >
> > --
> > 2.41.0
> >