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Howlett" , "Uladzislau Rezki" , "Miguel Ojeda" , "Boqun Feng" , "Gary Guo" , =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= , "Benno Lossin" , "Andreas Hindborg" , "Alice Ryhl" , "Trevor Gross" , "Daniel Almeida" , "Tamir Duberstein" , =?utf-8?q?Onur_=C3=96zkan?= , "David Airlie" , "Simona Vetter" , "John Hubbard" , "Alistair Popple" , "Timur Tabi" , , , , , "dri-devel" Subject: Re: [PATCH v3 7/8] gpu: nova-core: add NVKV typed decoding From: "Eliot Courtney" To: "Alexandre Courbot" , "Eliot Courtney" X-Mailer: aerc 0.22.0-0-gc2f86b7abde3 References: <20260928-b4-nvkv-v3-0-f04504c262c2@nvidia.com> <20260928-b4-nvkv-v3-7-f04504c262c2@nvidia.com> In-Reply-To: X-ClientProxiedBy: TYCPR01CA0148.jpnprd01.prod.outlook.com (2603:1096:400:2b7::7) To DS0PR12MB6413.namprd12.prod.outlook.com (2603:10b6:8:ce::10) Precedence: bulk X-Mailing-List: nova-gpu@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DS0PR12MB6413:EE_|DS7PR12MB6333:EE_ X-MS-Office365-Filtering-Correlation-Id: 6bdfdb45-4378-4018-b130-08df2abb139d X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|7416014|376014|10070799003|1800799024|23010399003|5023799004|261009223027099003|56012099006|4143699003|11063799006|10067099003|18002099003|22082099003|3023799007; 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Add some common `Schema` kinds, >> such as `Array` which collects an array value into a fixed maximum size >> array, and `Required` which fails a decode if the value is not sent. >> >> Signed-off-by: Eliot Courtney >> --- >> drivers/gpu/nova-core/gsp/nvkv.rs | 11 +- >> drivers/gpu/nova-core/gsp/nvkv/decode.rs | 622 ++++++++++++++++++++++++= ++++++- >> 2 files changed, 628 insertions(+), 5 deletions(-) >> >> diff --git a/drivers/gpu/nova-core/gsp/nvkv.rs b/drivers/gpu/nova-core/g= sp/nvkv.rs >> index 7ac3a459a98b..5791df07a7fa 100644 >> --- a/drivers/gpu/nova-core/gsp/nvkv.rs >> +++ b/drivers/gpu/nova-core/gsp/nvkv.rs >> @@ -9,7 +9,7 @@ >> //! function calls will map to some struct - for example, f(GPU_NAME_ST= RING_KEY, 0, b"some gpu") >> //! naturally maps to storing a &str with the GPU name. >> =20 >> -#![expect(unused_imports)] >> +#![cfg_attr(not(CONFIG_KUNIT), expect(unused_imports))] >> #![cfg_attr(not(CONFIG_KUNIT), expect(unused_macros))] >> =20 >> use core::{ >> @@ -23,7 +23,8 @@ >> use kernel::{ >> alloc::{ >> allocator::KVmalloc, >> - Allocator, // >> + Allocator, >> + ArrayVec, // >> }, >> bitfield, >> num::Bounded, >> @@ -148,6 +149,12 @@ fn default() -> Self { >> } >> } >> =20 >> +/// A schema field for an array value under the NVKV key `KEY_ID`. >> +#[repr(transparent)] > > I see that `#[repr(transparent)]` is used several times in this series, > but is there a need for it? Same for the many `#[inline]`s, here I feel > like letting the compiler arrange things as it wants might be the better > call. I know I suggested downgrading from always-inline to just inline, > so maybe we should go all the way here. These are very likely to be > inlined anyway, and worst case I don't think a function call would > induce a big cost. It's not required. I was adding that because I was thinking of these types semantically as just being type-level only wrappers of the underlying data. I'll remove them, plus the inlines. > > <...> >> +impl Schema for Key { >> + type Target =3D T; >> + >> + #[inline] >> + fn init() -> impl Init { >> + Self::default() >> + } >> + >> + #[inline] >> + fn finish(&mut self) -> impl Init + '_ { >> + Ok(core::mem::take(&mut self.0)) >> + } >> +} > > Both methods return the built value on the stack, which is fine when we > only deal with scalars but technically we could also store larger > values. How about a `const_assert!` ensuring we don't go beyond, say, 32 > bytes for the size of `T` and `Target`? Will so do! > > <...> >> +/// A schema field for a key that must be present. >> +/// >> +/// `finish` fails with `EINVAL` if no value arrived for the key. >> +#[repr(transparent)] >> +pub(crate) struct Required(Key, KEY_I= D>); >> + >> +impl Schema for Required { >> + type Target =3D T; >> + >> + #[inline] >> + fn init() -> impl Init { >> + Self(None.into()) >> + } >> + >> + #[inline] >> + fn finish(&mut self) -> impl Init + '_ { >> + (self.0).0.take().ok_or(EINVAL) > > I've experimented a bit with my earlier suggestion of having a wrapping > `Required` type because I wasn't so sure it would work, but it seems to > be indeed doable! Here is my draft implementation: > > pub(crate) struct Required { > inner: S, > parsed: bool, > } > > impl Schema for Required { > type Target =3D S::Target; > > fn init() -> impl Init { > init!(Self { inner <- S::init(), parsed: false }) > } > > fn finish(&mut self) -> impl Init + '_ { > // Reset `self.parsed` to make the schema empty again per the met= hod contract. > let parsed =3D core::mem::take(&mut self.parsed); > self.inner > .finish() > .chain(move |_| if parsed { Ok(()) } else { Err(EINVAL) }) > } > } > > impl<'data, S: Schema + Visit<'data>> Visit<'data> for Required { > fn visit(&mut self, key: KeyId, index: Index, value: DecoderValue<'da= ta>) -> Result { > let consumed =3D self.inner.visit(key, index, value)?; > self.parsed |=3D consumed; > Ok(consumed) > } > } > > You need to convert all the `Required` into `Required ...>>`, but this reads more logically I think, and now you can combine > `Required` with more types. I believe you could also implement > `Optional` in a similar way. > > (you will also need to add a `#[derive(Default)]` to `FbRegionFlags` on > the next patch, but that's not a big deal since it wraps a primitive > type anyway) Thanks for prototyping this, will add this in.