1 // Copyright 2023, The Android Open Source Project
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 //     http://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14 
15 use core::fmt;
16 use core::result;
17 
18 /// Standard SMCCC TRNG error values as described in DEN 0098 1.0 REL0.
19 #[derive(Debug, Clone, PartialEq)]
20 pub enum Error {
21     /// The call is not supported by the implementation.
22     NotSupported,
23     /// One of the call parameters has a non-supported value.
24     InvalidParameter,
25     /// Call returned without the requested entropy bits.
26     NoEntropy,
27     /// Negative values indicate error.
28     Unknown(i64),
29     /// The call returned a positive value when 0 was expected.
30     Unexpected(u64),
31 }
32 
33 impl fmt::Display for Error {
fmt(&self, f: &mut fmt::Formatter) -> fmt::Result34     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
35         match self {
36             Self::NotSupported => write!(f, "SMCCC TRNG call not supported"),
37             Self::InvalidParameter => write!(f, "SMCCC TRNG call received non-supported value"),
38             Self::NoEntropy => write!(f, "SMCCC TRNG call returned no entropy"),
39             Self::Unexpected(v) => write!(f, "Unexpected SMCCC TRNG return value {} ({0:#x})", v),
40             Self::Unknown(e) => write!(f, "Unknown SMCCC TRNG return value {} ({0:#x})", e),
41         }
42     }
43 }
44 
45 impl From<i64> for Error {
from(value: i64) -> Self46     fn from(value: i64) -> Self {
47         match value {
48             -1 => Error::NotSupported,
49             -2 => Error::InvalidParameter,
50             -3 => Error::NoEntropy,
51             _ if value < 0 => Error::Unknown(value),
52             _ => Error::Unexpected(value as u64),
53         }
54     }
55 }
56 
57 pub type Result<T> = result::Result<T, Error>;
58 
59 /// A version of the SMCCC TRNG interface.
60 #[derive(Copy, Clone, Eq, Ord, PartialEq, PartialOrd)]
61 pub struct Version {
62     pub major: u16,
63     pub minor: u16,
64 }
65 
66 impl fmt::Display for Version {
fmt(&self, f: &mut fmt::Formatter) -> fmt::Result67     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
68         write!(f, "{}.{}", self.major, self.minor)
69     }
70 }
71 
72 impl fmt::Debug for Version {
fmt(&self, f: &mut fmt::Formatter) -> fmt::Result73     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
74         fmt::Display::fmt(self, f)
75     }
76 }
77 
78 impl TryFrom<i32> for Version {
79     type Error = Error;
80 
try_from(value: i32) -> core::result::Result<Self, Error>81     fn try_from(value: i32) -> core::result::Result<Self, Error> {
82         if value < 0 {
83             Err((value as i64).into())
84         } else {
85             Ok(Self { major: (value >> 16) as u16, minor: value as u16 })
86         }
87     }
88 }
89 
90 impl From<Version> for u32 {
from(version: Version) -> Self91     fn from(version: Version) -> Self {
92         (u32::from(version.major) << 16) | u32::from(version.minor)
93     }
94 }
95