Add a few block subsystem constants to the rust `kernel::block` name space.
This makes it easier to access the constants from rust code.

Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
 rust/kernel/block.rs | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/rust/kernel/block.rs b/rust/kernel/block.rs
index 150f710efe5b..7461adf4d7e0 100644
--- a/rust/kernel/block.rs
+++ b/rust/kernel/block.rs
@@ -3,3 +3,15 @@
 //! Types for working with the block layer.
 
 pub mod mq;
+
+/// Bit mask for masking out [`SECTOR_SIZE`]
+pub const SECTOR_MASK: u32 = bindings::SECTOR_MASK;
+
+/// Sectors are size `1 << SECTOR_SHIFT`.
+pub const SECTOR_SHIFT: u32 = bindings::SECTOR_SHIFT;
+
+/// Size of a sector.
+pub const SECTOR_SIZE: u32 = bindings::SECTOR_SIZE;
+
+/// Power of two difference in size of a page and size of a sector.
+pub const PAGE_SECTORS_SHIFT: u32 = bindings::PAGE_SECTORS_SHIFT;

-- 
2.47.2

> On 11 Jul 2025, at 08:43, Andreas Hindborg <a.hindborg@kernel.org> wrote:
> 
> Add a few block subsystem constants to the rust `kernel::block` name space.
> This makes it easier to access the constants from rust code.
> 
> Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
> ---
> rust/kernel/block.rs | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
> 
> diff --git a/rust/kernel/block.rs b/rust/kernel/block.rs
> index 150f710efe5b..7461adf4d7e0 100644
> --- a/rust/kernel/block.rs
> +++ b/rust/kernel/block.rs
> @@ -3,3 +3,15 @@
> //! Types for working with the block layer.
> 
> pub mod mq;
> +
> +/// Bit mask for masking out [`SECTOR_SIZE`]

Missing period.

> +pub const SECTOR_MASK: u32 = bindings::SECTOR_MASK;
> +
> +/// Sectors are size `1 << SECTOR_SHIFT`.
> +pub const SECTOR_SHIFT: u32 = bindings::SECTOR_SHIFT;
> +
> +/// Size of a sector.
> +pub const SECTOR_SIZE: u32 = bindings::SECTOR_SIZE;
> +
> +/// Power of two difference in size of a page and size of a sector.

A bit hard to parse this.

Maybe “The difference between the size of a page and the size of a sector,
expressed as a power of two” ?

> +pub const PAGE_SECTORS_SHIFT: u32 = bindings::PAGE_SECTORS_SHIFT;
> 
> -- 
> 2.47.2
> 
> 
> 


 let sector: usize = something;
 let page_offset = (sector & block::SECTOR_MASK as usize) << block::SECTOR_SHIFT;


Wait, the parenthesis evaluate to usize, and the shift is a u32. How does this compile?

— Daniel

"Daniel Almeida" <daniel.almeida@collabora.com> writes:

>> On 11 Jul 2025, at 08:43, Andreas Hindborg <a.hindborg@kernel.org> wrote:
>>
>> Add a few block subsystem constants to the rust `kernel::block` name space.
>> This makes it easier to access the constants from rust code.
>>
>> Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
>> ---
>> rust/kernel/block.rs | 12 ++++++++++++
>> 1 file changed, 12 insertions(+)
>>
>> diff --git a/rust/kernel/block.rs b/rust/kernel/block.rs
>> index 150f710efe5b..7461adf4d7e0 100644
>> --- a/rust/kernel/block.rs
>> +++ b/rust/kernel/block.rs
>> @@ -3,3 +3,15 @@
>> //! Types for working with the block layer.
>>
>> pub mod mq;
>> +
>> +/// Bit mask for masking out [`SECTOR_SIZE`]
>
> Missing period.

Thanks.

>
>> +pub const SECTOR_MASK: u32 = bindings::SECTOR_MASK;
>> +
>> +/// Sectors are size `1 << SECTOR_SHIFT`.
>> +pub const SECTOR_SHIFT: u32 = bindings::SECTOR_SHIFT;
>> +
>> +/// Size of a sector.
>> +pub const SECTOR_SIZE: u32 = bindings::SECTOR_SIZE;
>> +
>> +/// Power of two difference in size of a page and size of a sector.
>
> A bit hard to parse this.
>
> Maybe “The difference between the size of a page and the size of a sector,
> expressed as a power of two” ?

OK.

>
>> +pub const PAGE_SECTORS_SHIFT: u32 = bindings::PAGE_SECTORS_SHIFT;
>>
>> --
>> 2.47.2
>>
>>
>>
>
>
>  let sector: usize = something;
>  let page_offset = (sector & block::SECTOR_MASK as usize) << block::SECTOR_SHIFT;
>
>
> Wait, the parenthesis evaluate to usize, and the shift is a u32. How does this compile?

That is all good. `Shl` has a ton of impls for integers [1].

Shifting more than 64 spaces on 64 bit system makes no sense anyway.

Best regards,
Andreas Hindborg


[1] https://doc.rust-lang.org/std/ops/trait.Shl.html

On Fri, Jul 11, 2025 at 01:43:11PM +0200, Andreas Hindborg wrote:
> Add a few block subsystem constants to the rust `kernel::block` name space.
> This makes it easier to access the constants from rust code.
> 
> Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
> ---
>  rust/kernel/block.rs | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/rust/kernel/block.rs b/rust/kernel/block.rs
> index 150f710efe5b..7461adf4d7e0 100644
> --- a/rust/kernel/block.rs
> +++ b/rust/kernel/block.rs
> @@ -3,3 +3,15 @@
>  //! Types for working with the block layer.
>  
>  pub mod mq;
> +
> +/// Bit mask for masking out [`SECTOR_SIZE`]
> +pub const SECTOR_MASK: u32 = bindings::SECTOR_MASK;
> +
> +/// Sectors are size `1 << SECTOR_SHIFT`.
> +pub const SECTOR_SHIFT: u32 = bindings::SECTOR_SHIFT;
> +
> +/// Size of a sector.
> +pub const SECTOR_SIZE: u32 = bindings::SECTOR_SIZE;
> +
> +/// Power of two difference in size of a page and size of a sector.
> +pub const PAGE_SECTORS_SHIFT: u32 = bindings::PAGE_SECTORS_SHIFT;

I was looking for the user to double-check whether u32 was the right
choice, but I can't find it. It looks like you don't use these yet?

Alice

"Alice Ryhl" <aliceryhl@google.com> writes:

> On Fri, Jul 11, 2025 at 01:43:11PM +0200, Andreas Hindborg wrote:
>> Add a few block subsystem constants to the rust `kernel::block` name space.
>> This makes it easier to access the constants from rust code.
>>
>> Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
>> ---
>>  rust/kernel/block.rs | 12 ++++++++++++
>>  1 file changed, 12 insertions(+)
>>
>> diff --git a/rust/kernel/block.rs b/rust/kernel/block.rs
>> index 150f710efe5b..7461adf4d7e0 100644
>> --- a/rust/kernel/block.rs
>> +++ b/rust/kernel/block.rs
>> @@ -3,3 +3,15 @@
>>  //! Types for working with the block layer.
>>
>>  pub mod mq;
>> +
>> +/// Bit mask for masking out [`SECTOR_SIZE`]
>> +pub const SECTOR_MASK: u32 = bindings::SECTOR_MASK;
>> +
>> +/// Sectors are size `1 << SECTOR_SHIFT`.
>> +pub const SECTOR_SHIFT: u32 = bindings::SECTOR_SHIFT;
>> +
>> +/// Size of a sector.
>> +pub const SECTOR_SIZE: u32 = bindings::SECTOR_SIZE;
>> +
>> +/// Power of two difference in size of a page and size of a sector.
>> +pub const PAGE_SECTORS_SHIFT: u32 = bindings::PAGE_SECTORS_SHIFT;
>
> I was looking for the user to double-check whether u32 was the right
> choice, but I can't find it. It looks like you don't use these yet?

Only `SECTOR_SHIFT` is used in this series, the rest will be used in the
future. They are used for memory backing rnull, still out of tree [1].
Do you want me to split the patch and delay the rest of the constants? I
fully intend to upstream the user as soon as I can.

It is a #define on C side used as a shift operator on usize in Rust code
like so:

  let sector: usize = something;
  let page_offset = (sector & block::SECTOR_MASK as usize) << block::SECTOR_SHIFT;

Best regards,
Andreas Hindborg


[1] https://git.kernel.org/pub/scm/linux/kernel/git/a.hindborg/linux.git/tree/drivers/block/rnull/rnull.rs?h=rnull-v6.15#n211