According to "Function return values and names" in coding-style.rst, the
dmar_ats_supported() function should return a boolean instead of an
integer. Also, rename "ret" to "supported" to be more straightforward.

Signed-off-by: Wei Wang <wei.w.wang@intel.com>
---
 drivers/iommu/intel/iommu.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index d8aa71305509..2778bfe14f36 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -2760,10 +2760,11 @@ static struct dmar_satc_unit *dmar_find_matched_satc_unit(struct pci_dev *dev)
 	return satcu;
 }
 
-static int dmar_ats_supported(struct pci_dev *dev, struct intel_iommu *iommu)
+static bool dmar_ats_supported(struct pci_dev *dev, struct intel_iommu *iommu)
 {
-	int i, ret = 1;
+	int i;
 	struct pci_bus *bus;
+	bool supported = true;
 	struct pci_dev *bridge = NULL;
 	struct device *tmp;
 	struct acpi_dmar_atsr *atsr;
@@ -2786,11 +2787,11 @@ static int dmar_ats_supported(struct pci_dev *dev, struct intel_iommu *iommu)
 		bridge = bus->self;
 		/* If it's an integrated device, allow ATS */
 		if (!bridge)
-			return 1;
+			return true;
 		/* Connected via non-PCIe: no ATS */
 		if (!pci_is_pcie(bridge) ||
 		    pci_pcie_type(bridge) == PCI_EXP_TYPE_PCI_BRIDGE)
-			return 0;
+			return false;
 		/* If we found the root port, look it up in the ATSR */
 		if (pci_pcie_type(bridge) == PCI_EXP_TYPE_ROOT_PORT)
 			break;
@@ -2809,11 +2810,11 @@ static int dmar_ats_supported(struct pci_dev *dev, struct intel_iommu *iommu)
 		if (atsru->include_all)
 			goto out;
 	}
-	ret = 0;
+	supported = false;
 out:
 	rcu_read_unlock();
 
-	return ret;
+	return supported;
 }
 
 int dmar_iommu_notify_scope_dev(struct dmar_pci_notify_info *info)
-- 
2.43.0

On 2025/5/9 22:00, Wei Wang wrote:
> According to "Function return values and names" in coding-style.rst, the
> dmar_ats_supported() function should return a boolean instead of an
> integer. Also, rename "ret" to "supported" to be more straightforward.
>

seems just a recommendation since this is just internal helper. The
function was indeed not well written anyhow. :) not sure if Baolu wants
take it or not. Taking it may make history tracking harder. Patch itself
looks good to me.

Reviewed-by: Yi Liu <yi.l.liu@intel.com>

> Signed-off-by: Wei Wang <wei.w.wang@intel.com>
> ---
>   drivers/iommu/intel/iommu.c | 13 +++++++------
>   1 file changed, 7 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index d8aa71305509..2778bfe14f36 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -2760,10 +2760,11 @@ static struct dmar_satc_unit *dmar_find_matched_satc_unit(struct pci_dev *dev)
>   	return satcu;
>   }
>   
> -static int dmar_ats_supported(struct pci_dev *dev, struct intel_iommu *iommu)
> +static bool dmar_ats_supported(struct pci_dev *dev, struct intel_iommu *iommu)
>   {
> -	int i, ret = 1;
> +	int i;
>   	struct pci_bus *bus;
> +	bool supported = true;
>   	struct pci_dev *bridge = NULL;
>   	struct device *tmp;
>   	struct acpi_dmar_atsr *atsr;

This list should have been in reverse Christmas tree order per the length. :)

> @@ -2786,11 +2787,11 @@ static int dmar_ats_supported(struct pci_dev *dev, struct intel_iommu *iommu)
>   		bridge = bus->self;
>   		/* If it's an integrated device, allow ATS */
>   		if (!bridge)
> -			return 1;
> +			return true;
>   		/* Connected via non-PCIe: no ATS */
>   		if (!pci_is_pcie(bridge) ||
>   		    pci_pcie_type(bridge) == PCI_EXP_TYPE_PCI_BRIDGE)
> -			return 0;
> +			return false;
>   		/* If we found the root port, look it up in the ATSR */
>   		if (pci_pcie_type(bridge) == PCI_EXP_TYPE_ROOT_PORT)
>   			break;
> @@ -2809,11 +2810,11 @@ static int dmar_ats_supported(struct pci_dev *dev, struct intel_iommu *iommu)
>   		if (atsru->include_all)
>   			goto out;
>   	}
> -	ret = 0;
> +	supported = false;
>   out:
>   	rcu_read_unlock();
>   
> -	return ret;
> +	return supported;
>   }
>   
>   int dmar_iommu_notify_scope_dev(struct dmar_pci_notify_info *info)

-- 
Regards,
Yi Liu

On Friday, May 9, 2025 5:27 PM, Liu, Yi L wrote:
/5/9 22:00, Wei Wang wrote:
> > According to "Function return values and names" in coding-style.rst,
> > the
> > dmar_ats_supported() function should return a boolean instead of an
> > integer. Also, rename "ret" to "supported" to be more straightforward.
> >
> 
> seems just a recommendation since this is just internal helper. The function
> was indeed not well written anyhow. :) not sure if Baolu wants take it or not.
> Taking it may make history tracking harder. Patch itself looks good to me.
> 
> Reviewed-by: Yi Liu <yi.l.liu@intel.com>

It seems mandatory to me from coding-style.rst:
"
Mixing up these two sorts of representations is a fertile source of
difficult-to-find bugs.  If the C language included a strong distinction
between integers and booleans then the compiler would find these mistakes
for us... but it doesn't.  To help prevent such bugs, always follow this
convention::

        If the name of a function is an action or an imperative command,
        the function should return an error-code integer.  If the name
        is a predicate, the function should return a "succeeded" boolean.
"

Another reason for making this change is that when we try to add more checks
inside this function (e.g., integrated_device_ats_supported() in patch 3), the added
new function needs to continue following the incorrect style. So, I thought, why
not change it from the foundation 😊