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However, it is useful to also be to represent I/O >>>> memory of a specific type, e.g. `u32 __iomem*` or `struct foo __iomem*= `. >>>> >>>> Thus, make `Mmio` generic on arbitrary `T`, where `T` is a sized type,= or a >>>> DST that implements `KnownSize`. Similar to the `MmioRaw` change, the >>>> existing behaviour is preserved in the form of `Mmio>`. T= his >>>> change brings the MMIO closer to the DMA coherent allocation types tha= t we >>>> have, which is already typed. >>>> >>>> To be able to implement `IoKnownSize`, add a `MIN_SIZE` constant to >>>> `KnownSize` trait to represent compile-time known minimum size of a >>>> specific type. >>>> >>>> Signed-off-by: Gary Guo >>>> --- >>>> rust/kernel/devres.rs | 2 +- >>>> rust/kernel/io.rs | 63 ++++++++++++++++++++++---------------= - >>>> rust/kernel/io/mem.rs | 4 +-- >>>> rust/kernel/io/poll.rs | 6 ++-- >>>> rust/kernel/io/register.rs | 19 +++++++----- >>>> rust/kernel/pci/io.rs | 2 +- >>>> rust/kernel/ptr.rs | 7 +++++ >>>> 7 files changed, 64 insertions(+), 39 deletions(-) >>>> >>>> diff --git a/rust/kernel/devres.rs b/rust/kernel/devres.rs >>>> index 65a4082122af..3e22c63efb98 100644 >>>> --- a/rust/kernel/devres.rs >>>> +++ b/rust/kernel/devres.rs >>>> @@ -106,7 +106,7 @@ struct Inner { >>>> /// } >>>> /// >>>> /// impl Deref for IoMem { >>>> -/// type Target =3D Mmio; >>>> +/// type Target =3D Mmio>; >>>> /// >>>> /// fn deref(&self) -> &Self::Target { >>>> /// // SAFETY: The memory range stored in `self` has been pro= perly mapped in `Self::new`. >>>> diff --git a/rust/kernel/io.rs b/rust/kernel/io.rs >>>> index d7f2145fa9b9..5a26b1e7e533 100644 >>>> --- a/rust/kernel/io.rs >>>> +++ b/rust/kernel/io.rs >>>> @@ -44,6 +44,8 @@ pub struct Region { >>>> } >>>> >>>> impl KnownSize for Region { >>>> + const MIN_SIZE: usize =3D SIZE; >>>> + >>>> #[inline(always)] >>>> fn size(p: *const Self) -> usize { >>>> (p as *const [u8]).len() >>>> @@ -169,7 +171,7 @@ pub fn size(&self) -> usize { >>>> /// } >>>> /// >>>> /// impl Deref for IoMem { >>>> -/// type Target =3D Mmio; >>>> +/// type Target =3D Mmio>; >>>> /// >>>> /// fn deref(&self) -> &Self::Target { >>>> /// // SAFETY: The memory range stored in `self` has been pro= perly mapped in `Self::new`. >>>> @@ -187,7 +189,7 @@ pub fn size(&self) -> usize { >>>> /// # } >>>> /// ``` >>>> #[repr(transparent)] >>>> -pub struct Mmio(MmioRaw>); >>>> +pub struct Mmio(MmioRaw); >>> >>> Why not have the `KnownSize` bound here? I think that would be more cle= ar. >>> >> >> There's no need to put bounds on structs unless you need them for `Drop`= or use >> of assoc types. > > I understand there is no technical need, but it would help communicating > how the code is intended to work. Unless I am mistaken, T will always be > `KnownSize`, right? I think most users don't need to know about this. All `T: Sized` will be `T= : KnownSize`, so if you're using it with a concrete type then the bound is already satisfied. The same argument can be said to document struct Coherent instead of just struct Coherent // ^ In this case the `drop` does need `KnownSize` bound But this just makes code more verbose as now you need to carry `?Sized` bou= nd everywhere. If there's nothing other than documentation purpose I'd prefer to just leav= e it out. Best, Gary > > > Best regards, > Andreas Hindborg