From cf9610f9116d55c5a66ef9f1faecacabd93a9322 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Mon, 24 Aug 2026 08:46:03 -0700 Subject: Merge tag 'pinctrl-v7.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-pinctrl Pull pin control updates from Linus Walleij: "Core changes: - Use the non-blocking mux_state_try_select() in the generic MUX pin control back-end - Free pin maps on pinctrl_generic_to_map() failure in the core helpers New hardware pin control: - Qualcomm Maili TLMM SoC, PMG1110 PMIC, and Eliza LPASS LPI TLMM SoC (this is for the low power audio, LPASS = Low Power Audio SubSystem portions) - Upboard support on top of the Intel pin controller - Apple T6030 and T6031 support (just compatible strings) - Samsung Exynos 8855 SoC - Mediatek MT6858 SoC - Rockchip RK3308B and RV1106 SoCs - Airoha EN7523 and AN7563 SoCs Improvements: - Qualcomm TLMM GPIOs are unconditionally marked as wakeup capable - Qualcomm improvements on top of the Qualcomm PDC (power domain controller) irqchip improvements from tglx:s tree - Qualcomm IPQ806x and IPQ9650 non-urgent pin grop fixups - The NPCM8xx driver has been put into shape fixing many pin and group definitions - Some non-urgent Tegra 264 pin assignments are fixed up - Some non-urgent fixups to Airoha AN7581 and AN7583 registers and pin assignments, missing features etc" * tag 'pinctrl-v7.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-pinctrl: (130 commits) dt-bindings: pinctrl: Convert TI DA850 pupd to DT schema pinctrl: meson: sync some modify from A4 pinctrl: meson: a4: Add input enable pin configuration pinctrl: realtek: rtd1625: remove unused group name spdif_sel pinctrl: realtek: rtd1625: fix base_bit for VE4 GPIO 13 dt-bindings: pinctrl: microchip,pic32mzda-pinctrl: Convert to DT schema Revert "Merge branch 'ib-rsk7204' into devel" pinctrl: rockchip: Add RV1106 pinctrl support dt-bindings: pinctrl: rockchip: Add RV1106 compatible pinctrl: rockchip: Decode drive strength in the get function pinctrl: fix PINCTRL_GENERIC_MUX not always being selectable pinctrl: airoha: add support of an7563 SoC dt-bindings: pinctrl: airoha: add support of an7563 pin controller pinctrl: airoha: try to find chip scu node by phandle first pinctrl: airoha: add support of en7523 SoC dt-bindings: pinctrl: airoha: add support of en7523 pin controller pinctrl: airoha: an7583: add support for olt pinmux pinctrl: airoha: an7583: add support for pon_alt pinmux pinctrl: airoha: an7583: add support for npu_uart pinmux dt-bindings: pinctrl: airoha: an7583: add missed features ... --- .../driver-api/driver-model/design-patterns.rst | 116 +++++++++++++++++++++ 1 file changed, 116 insertions(+) create mode 100644 Documentation/driver-api/driver-model/design-patterns.rst (limited to 'Documentation/driver-api/driver-model/design-patterns.rst') diff --git a/Documentation/driver-api/driver-model/design-patterns.rst b/Documentation/driver-api/driver-model/design-patterns.rst new file mode 100644 index 000000000..965b2b93b --- /dev/null +++ b/Documentation/driver-api/driver-model/design-patterns.rst @@ -0,0 +1,116 @@ +============================= +Device Driver Design Patterns +============================= + +This document describes a few common design patterns found in device drivers. +It is likely that subsystem maintainers will ask driver developers to +conform to these design patterns. + +1. State Container +2. container_of() + + +1. State Container +~~~~~~~~~~~~~~~~~~ + +While the kernel contains a few device drivers that assume that they will +only be probed() once on a certain system (singletons), it is custom to assume +that the device the driver binds to will appear in several instances. This +means that the probe() function and all callbacks need to be reentrant. + +The most common way to achieve this is to use the state container design +pattern. It usually has this form:: + + struct foo { + spinlock_t lock; /* Example member */ + (...) + }; + + static int foo_probe(...) + { + struct foo *foo; + + foo = devm_kzalloc(dev, sizeof(*foo), GFP_KERNEL); + if (!foo) + return -ENOMEM; + spin_lock_init(&foo->lock); + (...) + } + +This will create an instance of struct foo in memory every time probe() is +called. This is our state container for this instance of the device driver. +Of course it is then necessary to always pass this instance of the +state around to all functions that need access to the state and its members. + +For example, if the driver is registering an interrupt handler, you would +pass around a pointer to struct foo like this:: + + static irqreturn_t foo_handler(int irq, void *arg) + { + struct foo *foo = arg; + (...) + } + + static int foo_probe(...) + { + struct foo *foo; + + (...) + ret = request_irq(irq, foo_handler, 0, "foo", foo); + } + +This way you always get a pointer back to the correct instance of foo in +your interrupt handler. + + +2. container_of() +~~~~~~~~~~~~~~~~~ + +Continuing on the above example we add an offloaded work:: + + struct foo { + spinlock_t lock; + struct workqueue_struct *wq; + struct work_struct offload; + (...) + }; + + static void foo_work(struct work_struct *work) + { + struct foo *foo = container_of(work, struct foo, offload); + + (...) + } + + static irqreturn_t foo_handler(int irq, void *arg) + { + struct foo *foo = arg; + + queue_work(foo->wq, &foo->offload); + (...) + } + + static int foo_probe(...) + { + struct foo *foo; + + foo->wq = create_singlethread_workqueue("foo-wq"); + INIT_WORK(&foo->offload, foo_work); + (...) + } + +The design pattern is the same for an hrtimer or something similar that will +return a single argument which is a pointer to a struct member in the +callback. + +container_of() is a macro defined in + +What container_of() does is to obtain a pointer to the containing struct from +a pointer to a member by a simple subtraction using the offsetof() macro from +standard C, which allows something similar to object oriented behaviours. +Notice that the contained member must not be a pointer, but an actual member +for this to work. + +We can see here that we avoid having global pointers to our struct foo * +instance this way, while still keeping the number of parameters passed to the +work function to a single pointer. -- cgit v1.3.1