Joel Fernandes
2025-Sep-10 18:10 UTC
[PATCH] rust: pci: add PCI interrupt allocation and management support
On Wed, Sep 10, 2025 at 10:47:05AM +0200, Danilo Krummrich wrote:> On Wed Sep 10, 2025 at 5:54 AM CEST, Joel Fernandes wrote: > > impl Device<device::Bound> { > > The Bound context is not enough for some of the methods below, some of them > require the Core context, more below.Actually my patch already does that, the diff format creates confusion. Some of the below methods (like alloc) are in fact added to the device::Core context.> > + /// Free all allocated IRQ vectors for this device. > > + /// > > + /// This should be called to release interrupt resources when they are no longer needed, > > + /// during driver unbind or removal. > > + pub fn free_irq_vectors(&self) { > > + // SAFETY: `self.as_raw` is guaranteed to be a pointer to a valid `struct pci_dev`. > > + // `pci_free_irq_vectors` is safe to call even if no vectors are currently allocated. > > + unsafe { bindings::pci_free_irq_vectors(self.as_raw()) }; > > + } > > This requires the Core context, but we should not provide this method at all to > begin with; it puts the burden on drivers to remember calling this. > Instead, alloc_irq_vectors() should register a devres object with > devres::register(), so this gets called automatically when the device is > unbound.Great idea, thanks I will try this out.> > Note that a cleanup through devres is not in conflict with the Core context > requirement.Got it.> > + /// Allocate IRQ vectors for this PCI device. > > + /// > > + /// Allocates between `min_vecs` and `max_vecs` interrupt vectors for the device. > > + /// The allocation will use MSI-X, MSI, or legacy interrupts based on the `irq_types` > > + /// parameter and hardware capabilities. When multiple types are specified, the kernel > > + /// will try them in order of preference: MSI-X first, then MSI, then legacy interrupts. > > + /// This is called during driver probe. > > + /// > > + /// # Arguments > > + /// > > + /// * `min_vecs` - Minimum number of vectors required > > + /// * `max_vecs` - Maximum number of vectors to allocate > > + /// * `irq_types` - Types of interrupts that can be used > > + /// > > + /// # Returns > > + /// > > + /// Returns the number of vectors successfully allocated, or an error if the allocation > > + /// fails or cannot meet the minimum requirement. > > + /// > > + /// # Examples > > + /// > > + /// ``` > > + /// // Allocate using any available interrupt type in the order mentioned above. > > + /// let nvecs = dev.alloc_irq_vectors(1, 32, IrqTypes::all())?; > > + /// > > + /// // Allocate MSI or MSI-X only (no legacy interrupts) > > + /// let msi_only = IrqTypes::default() > > + /// .with(IrqType::Msi) > > + /// .with(IrqType::MsiX); > > + /// let nvecs = dev.alloc_irq_vectors(4, 16, msi_only)?; > > + /// ``` > > + pub fn alloc_irq_vectors( > > + &self, > > + min_vecs: u32, > > + max_vecs: u32, > > + irq_types: IrqTypes, > > + ) -> Result<u32> { > > + // SAFETY: `self.as_raw` is guaranteed to be a pointer to a valid `struct pci_dev`. > > + // `pci_alloc_irq_vectors` internally validates all parameters and returns error codes. > > + let ret = unsafe { > > + bindings::pci_alloc_irq_vectors(self.as_raw(), min_vecs, max_vecs, irq_types.raw()) > > + }; > > + > > + to_result(ret)?; > > + Ok(ret as u32) > > + } > > This is only valid to be called from the Core context, as it modifies internal > fields of the inner struct device.It is called from core context, the diff format confuses.> > Also, it would be nice if it would return a new type that can serve as argument > for irq_vector(), such that we don't have to rely on random integers.Makes sense, I will do that.> > + > > + /// Get the Linux IRQ number for a specific vector. > > + /// > > + /// This is called during driver probe after successful IRQ allocation > > + /// to obtain the IRQ numbers for registering interrupt handlers. > > + /// > > + /// # Arguments > > + /// > > + /// * `vector` - The vector index (0-based) > > + /// > > + /// # Returns > > + /// > > + /// Returns the Linux IRQ number for the specified vector, or an error if the vector > > + /// index is invalid or no vectors are allocated. > > + pub fn irq_vector(&self, vector: u32) -> Result<u32> { > > This method is already staged for inclusion in v6.18 in driver-core-next. Please > make sure to base changes on top of the tree mentioned in the maintainers file, > driver-core in this case. > > The signature of the existing method is: > > pub fn irq_vector(&self, index: u32) -> Result<IrqRequest<'_>> > > We return an IrqRequest, which captures the IRQ number *and* the corresponding > device, such that you can't get the combination wrong. > > Maybe it's worth looking at improving the index argument with a new type as > mentioned above.Ah Ok, thanks for pointing this out. I will rebase and reuse this. thanks, - Joel> > > + // SAFETY: `self.as_raw` is guaranteed to be a pointer to a valid `struct pci_dev`. > > + let irq = unsafe { bindings::pci_irq_vector(self.as_raw(), vector) }; > > + > > + to_result(irq)?; > > + Ok(irq as u32) > > + } > > }
Joel Fernandes
2025-Sep-10 19:02 UTC
[PATCH] rust: pci: add PCI interrupt allocation and management support
On Wed, Sep 10, 2025 at 02:09:55PM -0400, Joel Fernandes wrote: [...]> > > + /// Allocate IRQ vectors for this PCI device. > > > + /// > > > + /// Allocates between `min_vecs` and `max_vecs` interrupt vectors for the device. > > > + /// The allocation will use MSI-X, MSI, or legacy interrupts based on the `irq_types` > > > + /// parameter and hardware capabilities. When multiple types are specified, the kernel > > > + /// will try them in order of preference: MSI-X first, then MSI, then legacy interrupts. > > > + /// This is called during driver probe. > > > + /// > > > + /// # Arguments > > > + /// > > > + /// * `min_vecs` - Minimum number of vectors required > > > + /// * `max_vecs` - Maximum number of vectors to allocate > > > + /// * `irq_types` - Types of interrupts that can be used > > > + /// > > > + /// # Returns > > > + /// > > > + /// Returns the number of vectors successfully allocated, or an error if the allocation > > > + /// fails or cannot meet the minimum requirement. > > > + /// > > > + /// # Examples > > > + /// > > > + /// ``` > > > + /// // Allocate using any available interrupt type in the order mentioned above. > > > + /// let nvecs = dev.alloc_irq_vectors(1, 32, IrqTypes::all())?; > > > + /// > > > + /// // Allocate MSI or MSI-X only (no legacy interrupts) > > > + /// let msi_only = IrqTypes::default() > > > + /// .with(IrqType::Msi) > > > + /// .with(IrqType::MsiX); > > > + /// let nvecs = dev.alloc_irq_vectors(4, 16, msi_only)?; > > > + /// ``` > > > + pub fn alloc_irq_vectors( > > > + &self, > > > + min_vecs: u32, > > > + max_vecs: u32, > > > + irq_types: IrqTypes, > > > + ) -> Result<u32> { > > > + // SAFETY: `self.as_raw` is guaranteed to be a pointer to a valid `struct pci_dev`. > > > + // `pci_alloc_irq_vectors` internally validates all parameters and returns error codes. > > > + let ret = unsafe { > > > + bindings::pci_alloc_irq_vectors(self.as_raw(), min_vecs, max_vecs, irq_types.raw()) > > > + }; > > > + > > > + to_result(ret)?; > > > + Ok(ret as u32) > > > + } > > > > This is only valid to be called from the Core context, as it modifies internal > > fields of the inner struct device. > > It is called from core context, the diff format confuses. > > > > Also, it would be nice if it would return a new type that can serve as argument > > for irq_vector(), such that we don't have to rely on random integers. > > Makes sense, I will do that. >By the way, the "ret" value returned by pci_alloc_irq_vectors() is the number of vectors, not the vector index. So basically there are 3 numbers that mean different things: 1. Number of vectors (as returned by alloc_irq_vectors). 2. Index of a vector (passed to pci_irq_vector). 3. The Linux IRQ number (passed to request_irq). And your point is well taken, in fact even in current code there is ambiguity: irq_vector() accepts a vector index, where as request_irq() accepts a Linux IRQ number, which are different numbers. I can try to clean that up as well but let me know if you had any other thoughts. In fact, I think Device<device::Bound>::request_irq() pci should just accept IrqRequest? thanks, - Joel
Danilo Krummrich
2025-Sep-15 09:48 UTC
[PATCH] rust: pci: add PCI interrupt allocation and management support
On Wed Sep 10, 2025 at 9:02 PM CEST, Joel Fernandes wrote:> On Wed, Sep 10, 2025 at 02:09:55PM -0400, Joel Fernandes wrote: > [...] >> > > + /// Allocate IRQ vectors for this PCI device. >> > > + /// >> > > + /// Allocates between `min_vecs` and `max_vecs` interrupt vectors for the device. >> > > + /// The allocation will use MSI-X, MSI, or legacy interrupts based on the `irq_types` >> > > + /// parameter and hardware capabilities. When multiple types are specified, the kernel >> > > + /// will try them in order of preference: MSI-X first, then MSI, then legacy interrupts. >> > > + /// This is called during driver probe. >> > > + /// >> > > + /// # Arguments >> > > + /// >> > > + /// * `min_vecs` - Minimum number of vectors required >> > > + /// * `max_vecs` - Maximum number of vectors to allocate >> > > + /// * `irq_types` - Types of interrupts that can be used >> > > + /// >> > > + /// # Returns >> > > + /// >> > > + /// Returns the number of vectors successfully allocated, or an error if the allocation >> > > + /// fails or cannot meet the minimum requirement. >> > > + /// >> > > + /// # Examples >> > > + /// >> > > + /// ``` >> > > + /// // Allocate using any available interrupt type in the order mentioned above. >> > > + /// let nvecs = dev.alloc_irq_vectors(1, 32, IrqTypes::all())?; >> > > + /// >> > > + /// // Allocate MSI or MSI-X only (no legacy interrupts) >> > > + /// let msi_only = IrqTypes::default() >> > > + /// .with(IrqType::Msi) >> > > + /// .with(IrqType::MsiX); >> > > + /// let nvecs = dev.alloc_irq_vectors(4, 16, msi_only)?; >> > > + /// ``` >> > > + pub fn alloc_irq_vectors( >> > > + &self, >> > > + min_vecs: u32, >> > > + max_vecs: u32, >> > > + irq_types: IrqTypes, >> > > + ) -> Result<u32> { >> > > + // SAFETY: `self.as_raw` is guaranteed to be a pointer to a valid `struct pci_dev`. >> > > + // `pci_alloc_irq_vectors` internally validates all parameters and returns error codes. >> > > + let ret = unsafe { >> > > + bindings::pci_alloc_irq_vectors(self.as_raw(), min_vecs, max_vecs, irq_types.raw()) >> > > + }; >> > > + >> > > + to_result(ret)?; >> > > + Ok(ret as u32) >> > > + } >> > >> > This is only valid to be called from the Core context, as it modifies internal >> > fields of the inner struct device. >> >> It is called from core context, the diff format confuses. >> > >> > Also, it would be nice if it would return a new type that can serve as argument >> > for irq_vector(), such that we don't have to rely on random integers. >> >> Makes sense, I will do that. >> > By the way, the "ret" value returned by pci_alloc_irq_vectors() is the number > of vectors, not the vector index.Sure, but the vector index passed to pci_irq_vector() must be in the range defined by the return value of pci_alloc_irq_vectors(). I thought of e.g. Range<pci::IrqVector> as return value. This way you can easily iterate it and prove that it's an allocated vector index.> So basically there are 3 numbers that mean > different things: > 1. Number of vectors (as returned by alloc_irq_vectors). > 2. Index of a vector (passed to pci_irq_vector). > 3. The Linux IRQ number (passed to request_irq). > > And your point is well taken, in fact even in current code there is > ambiguity: irq_vector() accepts a vector index, where as request_irq() > accepts a Linux IRQ number, which are different numbers. I can try to clean > that up as well but let me know if you had any other thoughts. In fact, I > think Device<device::Bound>::request_irq() pci should just accept IrqRequest?Currently, pci::Device::request_irq() takes an IRQ vector index and calls irq_vector() internally to convert the vector index into an IRQ number. I'd keep this semantics, but introduce a new type IrqVector rather than using the raw integer. So, drivers would call // `irq_vecs` is of type `Range<pci::IrqVector>`. let irq_vecs = dev.alloc_irq_vectors(1, 1, pci::IrqTypes::ANY)?; let irq = KBox::pin_init( dev.request_irq(irq_vecs.start, ...)?, )?; Alternatively, to request all of them, if we have multiple, we can leverage KBox::pin_slice(), which will land in v6.18 (see alloc-next or rust-next branch in the Rust tree), so all irq::Registration objects can be stored in a single allocation.