Add initial interconnect (icc_path) Rust abstractions

[PATCH DNM 2/2] interconnect: Add a test Rust consumer driver

Posted by Konrad Dybcio 6 months, 3 weeks ago

From: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>

Do not merge, this is for illustration / CI purposes only.

Signed-off-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
---
 drivers/interconnect/Makefile |  1 +
 drivers/interconnect/test.rs  | 47 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 48 insertions(+)

diff --git a/drivers/interconnect/Makefile b/drivers/interconnect/Makefile
index b0a9a6753b9dc30083781163ccc01dafcfcd0485..913b92080cc0b79846b74c239e14959b45b5450c 100644
--- a/drivers/interconnect/Makefile
+++ b/drivers/interconnect/Makefile
@@ -2,6 +2,7 @@
 
 CFLAGS_core.o				:= -I$(src)
 icc-core-objs				:= core.o bulk.o debugfs-client.o
+icc-core-$(CONFIG_RUST)			+= test.o
 
 obj-$(CONFIG_INTERCONNECT)		+= icc-core.o
 obj-$(CONFIG_INTERCONNECT_IMX)		+= imx/
diff --git a/drivers/interconnect/test.rs b/drivers/interconnect/test.rs
new file mode 100644
index 0000000000000000000000000000000000000000..f4ba2000d0f1fd2d91aedf8aace0b0b54bfd48f2
--- /dev/null
+++ b/drivers/interconnect/test.rs
@@ -0,0 +1,47 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) Qualcomm Technologies, Inc. and/or its subsidiaries.
+
+//! Test interconnect consumer driver
+use kernel::{
+    c_str, device::Core, icc::*, module_platform_driver, of, of::DeviceId, platform, prelude::*,
+};
+
+#[pin_data]
+struct IccTestConsumerDriver {
+    #[pin]
+    path: IccPath,
+}
+
+kernel::of_device_table!(
+    OF_TABLE,
+    MODULE_OF_TABLE,
+    <IccTestConsumerDriver as platform::Driver>::IdInfo,
+    [(DeviceId::new(c_str!("linux,icc-consumer-test")), ())]
+);
+
+impl platform::Driver for IccTestConsumerDriver {
+    type IdInfo = ();
+    const OF_ID_TABLE: Option<of::IdTable<Self::IdInfo>> = Some(&OF_TABLE);
+
+    fn probe(
+        pdev: &platform::Device<Core>,
+        _id_info: Option<&Self::IdInfo>,
+    ) -> Result<Pin<KBox<Self>>> {
+        let path = IccPath::of_get(pdev.as_ref(), None)?;
+
+        path.set_bw(
+            IccBwUnit::from_megabits_per_sec(400),
+            IccBwUnit::from_megabits_per_sec(800),
+        )?;
+
+        Ok(KBox::pin_init(Self { path }, GFP_KERNEL)?.into())
+    }
+}
+
+module_platform_driver! {
+    type: IccTestConsumerDriver,
+    name: "icc-test-consumer",
+    authors: ["Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>"],
+    description: "Test interconnect consumer driver",
+    license: "GPL",
+}

-- 
2.50.1

Re: [PATCH DNM 2/2] interconnect: Add a test Rust consumer driver

Posted by Daniel Almeida 6 months, 3 weeks ago

Hi Konrad, commenting in case this driver goes forward.

> On 22 Jul 2025, at 18:14, Konrad Dybcio <konradybcio@kernel.org> wrote:
> 
> From: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
> 
> Do not merge, this is for illustration / CI purposes only.
> 
> Signed-off-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
> ---
> drivers/interconnect/Makefile |  1 +
> drivers/interconnect/test.rs  | 47 +++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 48 insertions(+)
> 
> diff --git a/drivers/interconnect/Makefile b/drivers/interconnect/Makefile
> index b0a9a6753b9dc30083781163ccc01dafcfcd0485..913b92080cc0b79846b74c239e14959b45b5450c 100644
> --- a/drivers/interconnect/Makefile
> +++ b/drivers/interconnect/Makefile
> @@ -2,6 +2,7 @@
> 
> CFLAGS_core.o := -I$(src)
> icc-core-objs := core.o bulk.o debugfs-client.o
> +icc-core-$(CONFIG_RUST) += test.o
> 
> obj-$(CONFIG_INTERCONNECT) += icc-core.o
> obj-$(CONFIG_INTERCONNECT_IMX) += imx/
> diff --git a/drivers/interconnect/test.rs b/drivers/interconnect/test.rs
> new file mode 100644
> index 0000000000000000000000000000000000000000..f4ba2000d0f1fd2d91aedf8aace0b0b54bfd48f2
> --- /dev/null
> +++ b/drivers/interconnect/test.rs
> @@ -0,0 +1,47 @@
> +// SPDX-License-Identifier: GPL-2.0
> +// Copyright (c) Qualcomm Technologies, Inc. and/or its subsidiaries.
> +
> +//! Test interconnect consumer driver
> +use kernel::{
> +    c_str, device::Core, icc::*, module_platform_driver, of, of::DeviceId, platform, prelude::*,
> +};
> +
> +#[pin_data]
> +struct IccTestConsumerDriver {
> +    #[pin]
> +    path: IccPath,
> +}

I don’t think this does anything useful without PhantomPinned, but Benno is
the right person to chime in here.

More importantly though, why do you have #[pin] on IccPath?

> +
> +kernel::of_device_table!(
> +    OF_TABLE,
> +    MODULE_OF_TABLE,
> +    <IccTestConsumerDriver as platform::Driver>::IdInfo,
> +    [(DeviceId::new(c_str!("linux,icc-consumer-test")), ())]
> +);
> +
> +impl platform::Driver for IccTestConsumerDriver {
> +    type IdInfo = ();
> +    const OF_ID_TABLE: Option<of::IdTable<Self::IdInfo>> = Some(&OF_TABLE);
> +
> +    fn probe(
> +        pdev: &platform::Device<Core>,
> +        _id_info: Option<&Self::IdInfo>,
> +    ) -> Result<Pin<KBox<Self>>> {
> +        let path = IccPath::of_get(pdev.as_ref(), None)?;
> +
> +        path.set_bw(
> +            IccBwUnit::from_megabits_per_sec(400),
> +            IccBwUnit::from_megabits_per_sec(800),
> +        )?;
> +
> +        Ok(KBox::pin_init(Self { path }, GFP_KERNEL)?.into())
> +    }
> +}
> +
> +module_platform_driver! {
> +    type: IccTestConsumerDriver,
> +    name: "icc-test-consumer",
> +    authors: ["Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>"],
> +    description: "Test interconnect consumer driver",
> +    license: "GPL",
> +}
> 
> -- 
> 2.50.1
> 
> 

— Daniel

Re: [PATCH DNM 2/2] interconnect: Add a test Rust consumer driver

Posted by Benno Lossin 6 months, 3 weeks ago

On Wed Jul 23, 2025 at 3:10 PM CEST, Daniel Almeida wrote:
> On 22 Jul 2025, at 18:14, Konrad Dybcio <konradybcio@kernel.org> wrote:
>> +#[pin_data]
>> +struct IccTestConsumerDriver {
>> +    #[pin]
>> +    path: IccPath,
>> +}
>
> I don’t think this does anything useful without PhantomPinned, but Benno is
> the right person to chime in here.

It does do something useful, there just has to be one type marked with
`#[pin]` that is `!Unpin` (so for example `PhantomPinned`, `Opaque<T>`
etc.).

In this case however, `IccPath` is a newtype of `*mut bindings::icc_path`
which isn't `PhantomPinned`, so this doesn't ensure that the
`IccTestConsumerDriver` will stay pinned after initializing.

> More importantly though, why do you have #[pin] on IccPath?

Another question is: why is `IccPath` not a newtype of
`Opaque<bindings::icc_path>`? And then one can use `&IccPath`.

---
Cheers,
Benno

Re: [PATCH DNM 2/2] interconnect: Add a test Rust consumer driver

Posted by Konrad Dybcio 1 month, 3 weeks ago

On 7/23/25 3:22 PM, Benno Lossin wrote:
> On Wed Jul 23, 2025 at 3:10 PM CEST, Daniel Almeida wrote:
>> On 22 Jul 2025, at 18:14, Konrad Dybcio <konradybcio@kernel.org> wrote:
>>> +#[pin_data]
>>> +struct IccTestConsumerDriver {
>>> +    #[pin]
>>> +    path: IccPath,
>>> +}
>>
>> I don’t think this does anything useful without PhantomPinned, but Benno is
>> the right person to chime in here.
> 
> It does do something useful, there just has to be one type marked with
> `#[pin]` that is `!Unpin` (so for example `PhantomPinned`, `Opaque<T>`
> etc.).
> 
> In this case however, `IccPath` is a newtype of `*mut bindings::icc_path`
> which isn't `PhantomPinned`, so this doesn't ensure that the
> `IccTestConsumerDriver` will stay pinned after initializing.
> 
>> More importantly though, why do you have #[pin] on IccPath?
> 
> Another question is: why is `IccPath` not a newtype of
> `Opaque<bindings::icc_path>`? And then one can use `&IccPath`.

The short answer to all of your questions happens to be the simple
"the code compiled"..  :) I didn't know about Opaque<T>, thanks

Konrad