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[PATCH 1/3] PCI: host-common: Add an API to check for any device under the Root Ports

Manivannan Sadhasivam posted 3 patches 3 months ago
[PATCH 1/3] PCI: host-common: Add an API to check for any device under the Root Ports
Posted by Manivannan Sadhasivam 3 months ago 
Some controller drivers need to check if there is any device available
under the Root Ports. So add an API that returns 'true' if a device is
found under any of the Root Ports, 'false' otherwise.

Controller drivers can use this API for usecases like turning off the
controller resources only if there are no devices under the Root Ports,
skipping PME_Turn_Off broadcast etc...

Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@oss.qualcomm.com>
---
 drivers/pci/controller/pci-host-common.c | 21 +++++++++++++++++++++
 drivers/pci/controller/pci-host-common.h |  2 ++
 2 files changed, 23 insertions(+)

diff --git a/drivers/pci/controller/pci-host-common.c b/drivers/pci/controller/pci-host-common.c
index 810d1c8de24e..6b4f90903dc6 100644
--- a/drivers/pci/controller/pci-host-common.c
+++ b/drivers/pci/controller/pci-host-common.c
@@ -17,6 +17,27 @@
 
 #include "pci-host-common.h"
 
+/**
+ * pci_root_ports_have_device - Check if the Root Ports under the Root bus have
+ *				any device underneath
+ * @dev: Root bus
+ *
+ * Return: true if a device is found, false otherwise
+ */
+bool pci_root_ports_have_device(struct pci_bus *root_bus)
+{
+	struct pci_bus *child;
+
+	/* Iterate over the Root Port busses and look for any device */
+	list_for_each_entry(child, &root_bus->children, node) {
+		if (list_count_nodes(&child->devices))
+			return true;
+	}
+
+	return false;
+}
+EXPORT_SYMBOL_GPL(pci_root_ports_have_device);
+
 static void gen_pci_unmap_cfg(void *ptr)
 {
 	pci_ecam_free((struct pci_config_window *)ptr);
diff --git a/drivers/pci/controller/pci-host-common.h b/drivers/pci/controller/pci-host-common.h
index 51c35ec0cf37..ff1c2ff98043 100644
--- a/drivers/pci/controller/pci-host-common.h
+++ b/drivers/pci/controller/pci-host-common.h
@@ -19,4 +19,6 @@ void pci_host_common_remove(struct platform_device *pdev);
 
 struct pci_config_window *pci_host_common_ecam_create(struct device *dev,
 	struct pci_host_bridge *bridge, const struct pci_ecam_ops *ops);
+
+bool pci_root_ports_have_device(struct pci_bus *root_bus);
 #endif
-- 
2.48.1
Re: [PATCH 1/3] PCI: host-common: Add an API to check for any device under the Root Ports
Posted by kernel test robot 3 months ago 
Hi Manivannan,

kernel test robot noticed the following build warnings:

[auto build test WARNING on pci/next]
[also build test WARNING on pci/for-linus linus/master v6.18-rc4 next-20251106]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Manivannan-Sadhasivam/PCI-host-common-Add-an-API-to-check-for-any-device-under-the-Root-Ports/20251106-141822
base:   https://git.kernel.org/pub/scm/linux/kernel/git/pci/pci.git next
patch link:    https://lore.kernel.org/r/20251106061326.8241-2-manivannan.sadhasivam%40oss.qualcomm.com
patch subject: [PATCH 1/3] PCI: host-common: Add an API to check for any device under the Root Ports
config: arm-randconfig-001-20251107 (https://download.01.org/0day-ci/archive/20251107/202511070717.PZBzRyQO-lkp@intel.com/config)
compiler: clang version 17.0.6 (https://github.com/llvm/llvm-project 6009708b4367171ccdbf4b5905cb6a803753fe18)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251107/202511070717.PZBzRyQO-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202511070717.PZBzRyQO-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> Warning: drivers/pci/controller/pci-host-common.c:27 function parameter 'root_bus' not described in 'pci_root_ports_have_device'

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
Re: [PATCH 1/3] PCI: host-common: Add an API to check for any device under the Root Ports
Posted by Konrad Dybcio 3 months ago 
On 11/6/25 7:13 AM, Manivannan Sadhasivam wrote:
> Some controller drivers need to check if there is any device available
> under the Root Ports. So add an API that returns 'true' if a device is
> found under any of the Root Ports, 'false' otherwise.
> 
> Controller drivers can use this API for usecases like turning off the
> controller resources only if there are no devices under the Root Ports,
> skipping PME_Turn_Off broadcast etc...
> 
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@oss.qualcomm.com>
> ---
>  drivers/pci/controller/pci-host-common.c | 21 +++++++++++++++++++++
>  drivers/pci/controller/pci-host-common.h |  2 ++
>  2 files changed, 23 insertions(+)
> 
> diff --git a/drivers/pci/controller/pci-host-common.c b/drivers/pci/controller/pci-host-common.c
> index 810d1c8de24e..6b4f90903dc6 100644
> --- a/drivers/pci/controller/pci-host-common.c
> +++ b/drivers/pci/controller/pci-host-common.c
> @@ -17,6 +17,27 @@
>  
>  #include "pci-host-common.h"
>  
> +/**
> + * pci_root_ports_have_device - Check if the Root Ports under the Root bus have
> + *				any device underneath
> + * @dev: Root bus
> + *
> + * Return: true if a device is found, false otherwise
> + */
> +bool pci_root_ports_have_device(struct pci_bus *root_bus)
> +{
> +	struct pci_bus *child;
> +
> +	/* Iterate over the Root Port busses and look for any device */
> +	list_for_each_entry(child, &root_bus->children, node) {
> +		if (list_count_nodes(&child->devices))

Is this list ever shrunk? I grepped around and couldn't find where
that happens

Konrad
Re: [PATCH 1/3] PCI: host-common: Add an API to check for any device under the Root Ports
Posted by Manivannan Sadhasivam 3 months ago 
On Thu, Nov 06, 2025 at 10:47:48AM +0100, Konrad Dybcio wrote:
> On 11/6/25 7:13 AM, Manivannan Sadhasivam wrote:
> > Some controller drivers need to check if there is any device available
> > under the Root Ports. So add an API that returns 'true' if a device is
> > found under any of the Root Ports, 'false' otherwise.
> > 
> > Controller drivers can use this API for usecases like turning off the
> > controller resources only if there are no devices under the Root Ports,
> > skipping PME_Turn_Off broadcast etc...
> > 
> > Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@oss.qualcomm.com>
> > ---
> >  drivers/pci/controller/pci-host-common.c | 21 +++++++++++++++++++++
> >  drivers/pci/controller/pci-host-common.h |  2 ++
> >  2 files changed, 23 insertions(+)
> > 
> > diff --git a/drivers/pci/controller/pci-host-common.c b/drivers/pci/controller/pci-host-common.c
> > index 810d1c8de24e..6b4f90903dc6 100644
> > --- a/drivers/pci/controller/pci-host-common.c
> > +++ b/drivers/pci/controller/pci-host-common.c
> > @@ -17,6 +17,27 @@
> >  
> >  #include "pci-host-common.h"
> >  
> > +/**
> > + * pci_root_ports_have_device - Check if the Root Ports under the Root bus have
> > + *				any device underneath
> > + * @dev: Root bus
> > + *
> > + * Return: true if a device is found, false otherwise
> > + */
> > +bool pci_root_ports_have_device(struct pci_bus *root_bus)
> > +{
> > +	struct pci_bus *child;
> > +
> > +	/* Iterate over the Root Port busses and look for any device */
> > +	list_for_each_entry(child, &root_bus->children, node) {
> > +		if (list_count_nodes(&child->devices))
> 
> Is this list ever shrunk? I grepped around and couldn't find where
> that happens
> 

So I digged into this and other 'pci_bus' lists, to my shock, none of list
entries were getting dropped. I'll send out fixes for all of them.

Thanks for catching this historical issue that no one noticed before :)

- Mani

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