[PATCH v2 1/8] device core: Introduce per-device MSI domain pointer

Stuart Yoder b08248 at gmail.com
Thu Jan 15 12:35:31 PST 2015

On Thu, Jan 8, 2015 at 11:06 AM, Marc Zyngier <marc.zyngier at arm.com> wrote:
> As MSI-type features are creeping into non-PCI devices, it is
> starting to make sense to give our struct device some form of
> support for this, by allowing a pointer to an MSI irq domain to
> be set/retrieved.
> Signed-off-by: Marc Zyngier <marc.zyngier at arm.com>
> ---
>  include/linux/device.h | 20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
> diff --git a/include/linux/device.h b/include/linux/device.h
> index fb50673..ec4cee5 100644
> --- a/include/linux/device.h
> +++ b/include/linux/device.h
> @@ -690,6 +690,7 @@ struct acpi_dev_node {
>   *             along with subsystem-level and driver-level callbacks.
>   * @pins:      For device pin management.
>   *             See Documentation/pinctrl.txt for details.
> + * @msi_domain: The generic MSI domain this device is using.
>   * @numa_node: NUMA node this device is close to.
>   * @dma_mask:  Dma mask (if dma'ble device).
>   * @coherent_dma_mask: Like dma_mask, but for alloc_coherent mapping as not all
> @@ -750,6 +751,9 @@ struct device {
>         struct dev_pm_info      power;
>         struct dev_pm_domain    *pm_domain;
> +       struct irq_domain       *msi_domain; /* MSI domain device uses */
> +#endif

This is not a comment on this patch specifically, but a question about other
MSI specific fields that might be needed in struct device.

Currently the generic MSI domain handling has hardcoded assumptions
that devices are PCI-- see the for_each_msi_entry() iterator in msi.h:

  #define dev_to_msi_list(dev)            (&to_pci_dev((dev))->msi_list)

  #define for_each_msi_entry(desc, dev)   \
        list_for_each_entry((desc), dev_to_msi_list((dev)), list)

One approach would be to move the msi_list out of pci_dev and put
it in struct device, so all devices can have an msi_list.

The other approach would be to keep msi_list in a bus specific
device struct, and then dev_to_msi_list() would need to be
implemented as a bus specific callback of some kind.

The above hardcoded PCI assumption isn't going to work.   Wanted to
see if there is any advice in which direction to go.

Stuart Yoder

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