Re: [PATCH 3/5] iommu: Add return errno rules to ->attach_dev ops

Nicolin Chen
2022-09-13T20:02:34Z

Hi Jeff,

On Tue, Sep 13, 2022 at 11:41:35AM -0700, Jeff Johnson wrote:
> > diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> > index ea30f00dc145..c5d7ec0187c7 100644
> > --- a/include/linux/iommu.h
> > +++ b/include/linux/iommu.h
> > @@ -266,6 +266,17 @@ struct iommu_ops {
> > /**
> > * struct iommu_domain_ops - domain specific operations
> > * @attach_dev: attach an iommu domain to a device
> > + * Rules of its return errno:
> > + * EINVAL - Exclusively, device and domain are incompatible. Must
> > + * avoid kernel prints along with this errno. Any EINVAL
> > + * returned from kAPIs must be converted to ENODEV if it
> > + * is device-specific, or to some other reasonable errno
> > + * being listed below
> > + * ENOMEM - Out of memory
> > + * ENOSPC - No space left on device
> > + * EBUSY - Device is attached to a domain and cannot be changed
> > + * ENODEV - Device specific errors, not able to be attached
> > + * <others> - Treated as ENODEV by the caller. Use is discouraged
>
> It is my understanding that kernel-doc won't preserve your formatting
> without extra directives. See the "Note" after
> <https://www.kernel.org/doc/html/latest/doc-guide/kernel-doc.html#return-values>

Thanks for the review!

Perhaps the following one would work:

diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index ea30f00dc145..14f078b58e17 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -266,6 +266,17 @@ struct iommu_ops {
/**
* struct iommu_domain_ops - domain specific operations
* @attach_dev: attach an iommu domain to a device
+ * Return:
+ * * 0 - success
+ * * EINVAL - Exclusively, device and domain are incompatible. Must avoid
+ * kernel prints along with this errno. Any EINVAL returned from
+ * a kAPI must be converted to ENODEV if it is device-specific,
+ * or to some other reasonable errno being listed below
+ * * ENOMEM - Out of memory
+ * * ENOSPC - No space left on device
+ * * EBUSY - Device is attached to a domain and cannot be changed
+ * * ENODEV - Device specific errors, not able to be attached
+ * * <others> - Treated as ENODEV by the caller. Use is discouraged
* @detach_dev: detach an iommu domain from a device
* @map: map a physically contiguous memory region to an iommu domain
* @map_pages: map a physically contiguous set of pages of the same size to