These accessors can be used to retrieve an IRQ from a platform device by
index or name. The IRQ can then be used to request the line using
irq::request::Registration::register() and
irq::request::ThreadedRegistration::register().

Signed-off-by: Daniel Almeida <daniel.almeida@collabora.com>
---
 rust/kernel/platform.rs | 52 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 52 insertions(+)

diff --git a/rust/kernel/platform.rs b/rust/kernel/platform.rs
index 4917cb34e2fe8027d3d861e90de51de85f006735..1acaebf38d99d06f93fa13b0b356671ea77ed97a 100644
--- a/rust/kernel/platform.rs
+++ b/rust/kernel/platform.rs
@@ -188,6 +188,58 @@ impl Device {
     fn as_raw(&self) -> *mut bindings::platform_device {
         self.0.get()
     }
+
+    /// Returns an IRQ for the device by index.
+    pub fn irq_by_index(&self, index: u32) -> Result<u32> {
+        // SAFETY: `self.as_raw` returns a valid pointer to a `struct platform_device`.
+        let res = unsafe { bindings::platform_get_irq(self.as_raw(), index) };
+
+        if res < 0 {
+            return Err(Error::from_errno(res));
+        }
+
+        Ok(res as u32)
+    }
+
+    /// Same as [`Self::irq_by_index`] but does not print an error message if an IRQ
+    /// cannot be obtained.
+    pub fn optional_irq_by_index(&self, index: u32) -> Result<u32> {
+        // SAFETY: `self.as_raw` returns a valid pointer to a `struct platform_device`.
+        let res = unsafe { bindings::platform_get_irq_optional(self.as_raw(), index) };
+
+        if res < 0 {
+            return Err(Error::from_errno(res));
+        }
+
+        Ok(res as u32)
+    }
+
+    /// Returns an IRQ for the device by name.
+    pub fn irq_by_name(&self, name: &CStr) -> Result<u32> {
+        // SAFETY: `self.as_raw` returns a valid pointer to a `struct platform_device`.
+        let res = unsafe { bindings::platform_get_irq_byname(self.as_raw(), name.as_char_ptr()) };
+
+        if res < 0 {
+            return Err(Error::from_errno(res));
+        }
+
+        Ok(res as u32)
+    }
+
+    /// Same as [`Self::irq_by_name`] but does not print an error message if an IRQ
+    /// cannot be obtained.
+    pub fn optional_irq_by_name(&self, name: &CStr) -> Result<u32> {
+        // SAFETY: `self.as_raw` returns a valid pointer to a `struct platform_device`.
+        let res = unsafe {
+            bindings::platform_get_irq_byname_optional(self.as_raw(), name.as_char_ptr())
+        };
+
+        if res < 0 {
+            return Err(Error::from_errno(res));
+        }
+
+        Ok(res as u32)
+    }
 }
 
 impl Deref for Device<device::Core> {

-- 
2.49.0

On Wed, May 14, 2025 at 04:20:52PM -0300, Daniel Almeida wrote:
> These accessors can be used to retrieve an IRQ from a platform device by
> index or name. The IRQ can then be used to request the line using
> irq::request::Registration::register() and
> irq::request::ThreadedRegistration::register().
> 
> Signed-off-by: Daniel Almeida <daniel.almeida@collabora.com>
> ---
>  rust/kernel/platform.rs | 52 +++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 52 insertions(+)
> 
> diff --git a/rust/kernel/platform.rs b/rust/kernel/platform.rs
> index 4917cb34e2fe8027d3d861e90de51de85f006735..1acaebf38d99d06f93fa13b0b356671ea77ed97a 100644
> --- a/rust/kernel/platform.rs
> +++ b/rust/kernel/platform.rs
> @@ -188,6 +188,58 @@ impl Device {
>      fn as_raw(&self) -> *mut bindings::platform_device {
>          self.0.get()
>      }
> +
> +    /// Returns an IRQ for the device by index.
> +    pub fn irq_by_index(&self, index: u32) -> Result<u32> {
> +        // SAFETY: `self.as_raw` returns a valid pointer to a `struct platform_device`.
> +        let res = unsafe { bindings::platform_get_irq(self.as_raw(), index) };
> +
> +        if res < 0 {
> +            return Err(Error::from_errno(res));
> +        }
> +
> +        Ok(res as u32)
> +    }
> +
> +    /// Same as [`Self::irq_by_index`] but does not print an error message if an IRQ
> +    /// cannot be obtained.
> +    pub fn optional_irq_by_index(&self, index: u32) -> Result<u32> {
> +        // SAFETY: `self.as_raw` returns a valid pointer to a `struct platform_device`.
> +        let res = unsafe { bindings::platform_get_irq_optional(self.as_raw(), index) };
> +
> +        if res < 0 {
> +            return Err(Error::from_errno(res));
> +        }
> +
> +        Ok(res as u32)
> +    }
> +
> +    /// Returns an IRQ for the device by name.
> +    pub fn irq_by_name(&self, name: &CStr) -> Result<u32> {
> +        // SAFETY: `self.as_raw` returns a valid pointer to a `struct platform_device`.
> +        let res = unsafe { bindings::platform_get_irq_byname(self.as_raw(), name.as_char_ptr()) };
> +
> +        if res < 0 {
> +            return Err(Error::from_errno(res));
> +        }
> +
> +        Ok(res as u32)
> +    }
> +
> +    /// Same as [`Self::irq_by_name`] but does not print an error message if an IRQ
> +    /// cannot be obtained.
> +    pub fn optional_irq_by_name(&self, name: &CStr) -> Result<u32> {
> +        // SAFETY: `self.as_raw` returns a valid pointer to a `struct platform_device`.
> +        let res = unsafe {
> +            bindings::platform_get_irq_byname_optional(self.as_raw(), name.as_char_ptr())
> +        };
> +
> +        if res < 0 {
> +            return Err(Error::from_errno(res));
> +        }
> +
> +        Ok(res as u32)
> +    }

I don't like the indirection of claiming a u32 representing the IRQ number from
a bus device and stuffing it into an irq::Registration.

It would be better we we'd make it impossible (or at least harder) for a driver
to pass the wrong number to irq::Registration.

I see two options:

  1) Make the platform::Device accessors themselves return an
     irq::Registration.

  2) Make the platform::Device accessors return some kind of transparent cookie,
     that drivers can't create themselves that can be fed into the
     irq::Registration.

My preference would be 1) if there's no major ergonomic issue with that.

Hi Danilo,

[…]

>> +
>> +    /// Same as [`Self::irq_by_name`] but does not print an error message if an IRQ
>> +    /// cannot be obtained.
>> +    pub fn optional_irq_by_name(&self, name: &CStr) -> Result<u32> {
>> +        // SAFETY: `self.as_raw` returns a valid pointer to a `struct platform_device`.
>> +        let res = unsafe {
>> +            bindings::platform_get_irq_byname_optional(self.as_raw(), name.as_char_ptr())
>> +        };
>> +
>> +        if res < 0 {
>> +            return Err(Error::from_errno(res));
>> +        }
>> +
>> +        Ok(res as u32)
>> +    }
> 
> I don't like the indirection of claiming a u32 representing the IRQ number from
> a bus device and stuffing it into an irq::Registration.
> 
> It would be better we we'd make it impossible (or at least harder) for a driver
> to pass the wrong number to irq::Registration.
> 
> I see two options:
> 
>  1) Make the platform::Device accessors themselves return an
>     irq::Registration.
> 
>  2) Make the platform::Device accessors return some kind of transparent cookie,
>     that drivers can't create themselves that can be fed into the
>     irq::Registration.
> 
> My preference would be 1) if there's no major ergonomic issue with that.

Isn’t 1 way more cluttered?

That's because the accessors would have to forward all of the arguments (i.e.:
currently 4) to register().

Going with approach 2 lets us keep the two APIs distinct, we'd only have to
take in the cookie in place of the u32, of course.

— Daniel

On Mon, Jun 02, 2025 at 11:56:28AM -0300, Daniel Almeida wrote:
> Hi Danilo,
> 
> […]
> 
> >> +
> >> +    /// Same as [`Self::irq_by_name`] but does not print an error message if an IRQ
> >> +    /// cannot be obtained.
> >> +    pub fn optional_irq_by_name(&self, name: &CStr) -> Result<u32> {
> >> +        // SAFETY: `self.as_raw` returns a valid pointer to a `struct platform_device`.
> >> +        let res = unsafe {
> >> +            bindings::platform_get_irq_byname_optional(self.as_raw(), name.as_char_ptr())
> >> +        };
> >> +
> >> +        if res < 0 {
> >> +            return Err(Error::from_errno(res));
> >> +        }
> >> +
> >> +        Ok(res as u32)
> >> +    }
> > 
> > I don't like the indirection of claiming a u32 representing the IRQ number from
> > a bus device and stuffing it into an irq::Registration.
> > 
> > It would be better we we'd make it impossible (or at least harder) for a driver
> > to pass the wrong number to irq::Registration.
> > 
> > I see two options:
> > 
> >  1) Make the platform::Device accessors themselves return an
> >     irq::Registration.
> > 
> >  2) Make the platform::Device accessors return some kind of transparent cookie,
> >     that drivers can't create themselves that can be fed into the
> >     irq::Registration.
> > 
> > My preference would be 1) if there's no major ergonomic issue with that.
> 
> Isn’t 1 way more cluttered?

I don't think so, your irq::Registration::register() function needs a reference
to the registering device anyways.

And given that, now that I think about it, it even has to be this way.

Otherwise, I could provide irq::Registration::register() an IRQ number that does
not belong to the bus device that is passed into irq::Registration::register().

So, irq::Registration::register() even needs to be unsafe, with the safety
requirement that the IRQ number must belong to the corresponding device and
should be wrapped by bus device abstractions providing the safe driver API.

> That's because the accessors would have to forward all of the arguments (i.e.:
> currently 4) to register().

It's only the additional arguments below, which you can also wrap in an
irq::Args structure to keep things cleaner. :)

+        flags: Flags,
+        name: &'static CStr,
+        handler: T,

On Wed May 14, 2025 at 9:20 PM CEST, Daniel Almeida wrote:
> +    /// Same as [`Self::irq_by_name`] but does not print an error message if an IRQ
> +    /// cannot be obtained.
> +    pub fn optional_irq_by_name(&self, name: &CStr) -> Result<u32> {
> +        // SAFETY: `self.as_raw` returns a valid pointer to a `struct platform_device`.
> +        let res = unsafe {
> +            bindings::platform_get_irq_byname_optional(self.as_raw(), name.as_char_ptr())
> +        };
> +
> +        if res < 0 {
> +            return Err(Error::from_errno(res));
> +        }
> +
> +        Ok(res as u32)

This patch could make much use of the function for `Error` that does the
last 4 lines.

---
Cheers,
Benno

> +    }
>  }
>  
>  impl Deref for Device<device::Core> {