linux-kernel - [PATCH v8 4/7] PCI: Document pci_bus_for_each

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Date:   Thu, 30 Mar 2023 19:24:31 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Mickaël Salaün <mic@...ikod.net>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Randy Dunlap <rdunlap@...radead.org>,
        Arnd Bergmann <arnd@...db.de>,
        Philippe Mathieu-Daudé <philmd@...aro.org>,
        Niklas Schnelle <schnelle@...ux.ibm.com>,
        Bjorn Helgaas <helgaas@...nel.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Pali Rohár <pali@...nel.org>,
        "Maciej W. Rozycki" <macro@...am.me.uk>,
        Juergen Gross <jgross@...e.com>,
        Dominik Brodowski <linux@...inikbrodowski.net>,
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        sparclinux@...r.kernel.org, linux-pci@...r.kernel.org,
        xen-devel@...ts.xenproject.org, linux-acpi@...r.kernel.org
Cc:     Miguel Ojeda <ojeda@...nel.org>,
        Richard Henderson <richard.henderson@...aro.org>,
        Ivan Kokshaysky <ink@...assic.park.msu.ru>,
        Matt Turner <mattst88@...il.com>,
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        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
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        John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>,
        "David S. Miller" <davem@...emloft.net>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>
Subject: [PATCH v8 4/7] PCI: Document pci_bus_for_each_resource() to avoid confusion

There might be a confusion with the implementation of the
pci_bus_for_each_resources() due to side effect of Logical
OR. Document entire macro and explain how it works and why
the conditional needs to be like that.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
---
 include/linux/pci.h | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/include/linux/pci.h b/include/linux/pci.h
index 5cacd9e4c8cd..e3b3af606280 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1446,6 +1446,26 @@ int devm_request_pci_bus_resources(struct device *dev,
 /* Temporary until new and working PCI SBR API in place */
 int pci_bridge_secondary_bus_reset(struct pci_dev *dev);
 
+/**
+ * pci_bus_for_each_resource - iterate over PCI bus resources
+ * @bus: the PCI bus
+ * @res: a varible to keep a pointer to the current resource
+ * @i: a variable to keep the index of the current resource
+ *
+ * Iterate over PCI bus resources. The first part is to go over PCI bus
+ * resource array, which has at most the %PCI_BRIDGE_RESOURCE_NUM entries.
+ * After that continue with the separate list of the additional resources,
+ * if not empty. That's why the Logical OR is being used.
+ *
+ * Possible usage:
+ *
+ *	struct pci_bus *bus = ...;
+ *	struct resource *res;
+ *	unsigned int i;
+ *
+ * 	pci_bus_for_each_resource(bus, res, i)
+ * 		pr_info("PCI bus resource[%u]: %pR\n", i, res);
+ */
 #define pci_bus_for_each_resource(bus, res, i)				\
 	for (i = 0;							\
 	    (res = pci_bus_resource_n(bus, i)) || i < PCI_BRIDGE_RESOURCE_NUM; \
-- 
2.40.0.1.gaa8946217a0b