diff options
Diffstat (limited to 'Documentation/driver-api/gpio')
| -rw-r--r-- | Documentation/driver-api/gpio/bt8xxgpio.rst | 62 | ||||
| -rw-r--r-- | Documentation/driver-api/gpio/driver.rst | 27 | ||||
| -rw-r--r-- | Documentation/driver-api/gpio/index.rst | 1 |
3 files changed, 80 insertions, 10 deletions
diff --git a/Documentation/driver-api/gpio/bt8xxgpio.rst b/Documentation/driver-api/gpio/bt8xxgpio.rst new file mode 100644 index 000000000000..d7e75f1234e7 --- /dev/null +++ b/Documentation/driver-api/gpio/bt8xxgpio.rst @@ -0,0 +1,62 @@ +=================================================================== +A driver for a selfmade cheap BT8xx based PCI GPIO-card (bt8xxgpio) +=================================================================== + +For advanced documentation, see https://bues.ch/cms/unmaintained/btgpio.html + +A generic digital 24-port PCI GPIO card can be built out of an ordinary +Brooktree bt848, bt849, bt878 or bt879 based analog TV tuner card. The +Brooktree chip is used in old analog Hauppauge WinTV PCI cards. You can easily +find them used for low prices on the net. + +The bt8xx chip does have 24 digital GPIO ports. +These ports are accessible via 24 pins on the SMD chip package. + + +How to physically access the GPIO pins +====================================== + +The are several ways to access these pins. One might unsolder the whole chip +and put it on a custom PCI board, or one might only unsolder each individual +GPIO pin and solder that to some tiny wire. As the chip package really is tiny +there are some advanced soldering skills needed in any case. + +The physical pinouts are drawn in the following ASCII art. +The GPIO pins are marked with G00-G23:: + + G G G G G G G G G G G G G G G G G G + 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 + | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | + --------------------------------------------------------------------------- + --| ^ ^ |-- + --| pin 86 pin 67 |-- + --| |-- + --| pin 61 > |-- G18 + --| |-- G19 + --| |-- G20 + --| |-- G21 + --| |-- G22 + --| pin 56 > |-- G23 + --| |-- + --| Brooktree 878/879 |-- + --| |-- + --| |-- + --| |-- + --| |-- + --| |-- + --| |-- + --| |-- + --| |-- + --| |-- + --| |-- + --| |-- + --| |-- + --| |-- + --| O |-- + --| |-- + --------------------------------------------------------------------------- + | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | + ^ + This is pin 1 + diff --git a/Documentation/driver-api/gpio/driver.rst b/Documentation/driver-api/gpio/driver.rst index 3fdb32422f8a..2ff743105927 100644 --- a/Documentation/driver-api/gpio/driver.rst +++ b/Documentation/driver-api/gpio/driver.rst @@ -5,7 +5,7 @@ GPIO Driver Interface This document serves as a guide for writers of GPIO chip drivers. Each GPIO controller driver needs to include the following header, which defines -the structures used to define a GPIO driver: +the structures used to define a GPIO driver:: #include <linux/gpio/driver.h> @@ -398,12 +398,15 @@ provided. A big portion of overhead code will be managed by gpiolib, under the assumption that your interrupts are 1-to-1-mapped to the GPIO line index: - GPIO line offset Hardware IRQ - 0 0 - 1 1 - 2 2 - ... ... - ngpio-1 ngpio-1 +.. csv-table:: + :header: GPIO line offset, Hardware IRQ + + 0,0 + 1,1 + 2,2 + ...,... + ngpio-1, ngpio-1 + If some GPIO lines do not have corresponding IRQs, the bitmask valid_mask and the flag need_valid_mask in gpio_irq_chip can be used to mask off some @@ -413,7 +416,9 @@ The preferred way to set up the helpers is to fill in the struct gpio_irq_chip inside struct gpio_chip before adding the gpio_chip. If you do this, the additional irq_chip will be set up by gpiolib at the same time as setting up the rest of the GPIO functionality. The following -is a typical example of a cascaded interrupt handler using gpio_irq_chip: +is a typical example of a cascaded interrupt handler using gpio_irq_chip:: + +.. code-block:: c /* Typical state container with dynamic irqchip */ struct my_gpio { @@ -448,7 +453,9 @@ is a typical example of a cascaded interrupt handler using gpio_irq_chip: return devm_gpiochip_add_data(dev, &g->gc, g); The helper support using hierarchical interrupt controllers as well. -In this case the typical set-up will look like this: +In this case the typical set-up will look like this:: + +.. code-block:: c /* Typical state container with dynamic irqchip */ struct my_gpio { @@ -493,7 +500,7 @@ available but we try to move away from this: gpiochip. It will pass the struct gpio_chip* for the chip to all IRQ callbacks, so the callbacks need to embed the gpio_chip in its state container and obtain a pointer to the container using container_of(). - (See Documentation/driver-model/design-patterns.txt) + (See Documentation/driver-api/driver-model/design-patterns.rst) - gpiochip_irqchip_add_nested(): adds a nested cascaded irqchip to a gpiochip, as discussed above regarding different types of cascaded irqchips. The diff --git a/Documentation/driver-api/gpio/index.rst b/Documentation/driver-api/gpio/index.rst index c5b8467f9104..5b61032aa4ea 100644 --- a/Documentation/driver-api/gpio/index.rst +++ b/Documentation/driver-api/gpio/index.rst @@ -13,6 +13,7 @@ Contents: board drivers-on-gpio legacy + bt8xxgpio Core ==== |