Messages in this thread | | | From | Linus Walleij <> | Date | Mon, 7 Aug 2017 11:03:53 +0200 | Subject | Re: [PATCH] serio: PS2 gpio bit banging driver for the serio bus |
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On Tue, Aug 1, 2017 at 12:24 AM, Danilo Krummrich <danilokrummrich@dk-develop.de> wrote:
> This driver provides PS2 serio bus support by implementing bit banging > with the GPIO API. The GPIO pins, data and clock, can be configured with > a node in the device tree or by static platform data. > > Writing to a device is supported as well, though it is not recommended as > the timings to be halt given by libps2 are very tough and difficult to > reach with bit banging. Therefore it can be configured (also in DT and > pdata) whether the serio write function should be available for clients. > > This driver is for development purposes and not for productive use. > However, this driver can be useful e.g. when no USB port is available or > using old peripherals is desired as PS2 controllers getting rare. > > This driver was tested on a RPI1 and on Hikey960 and it worked well > together with the atkbd driver. > > Signed-off-by: Danilo Krummrich <danilokrummrich@dk-develop.de>
> +++ b/Documentation/devicetree/bindings/serio/ps2-gpio.txt
When you add DT bindings you have to CC devicetree@vger.kernel.org
> @@ -0,0 +1,20 @@ > +Device-Tree bindings for ps2 gpio driver > + > +Required properties: > + - compatible = "ps2-gpio"; > + - gpios: data and clock gpio > + > +Optional properties: > + - ps2-gpio,write-enable: Indicates whether write function is provided > + to serio device. Most probably providing the write fn will not work, > + because of the tough timing libps2 requires. > + > +Example nodes: > + > +ps2@0 { > + compatible = "ps2-gpio"; > + gpios = <&gpio 24 0 /* data */ > + &gpio 23 0 /* clock */ > + >; > + i2c-gpio,write-enable = <0>; > +};
These look fine to me though.
> diff --git a/Documentation/gpio/drivers-on-gpio.txt b/Documentation/gpio/drivers-on-gpio.txt
Thanks for patching this!
> +config SERIO_GPIO_PS2 > + tristate "GPIO PS/2 bit banging driver" > + help > + Say Y here if you want PS/2 bit banging support via GPIO. > + > + To compile this driver as a module, choose M here: the > + module will be called gpio-ps2. > + > + If you are unsure, say N.
As mentioned
depends on GPIOLIB depends on OF
> +#include <linux/gpio.h>
Use only:
#include <linux/gpio/consumer.h>
> +#include <linux/of_gpio.h>
Should not be needed.
> +struct ps2_gpio_data { > + struct device *dev; > + struct serio *serio; > + unsigned char mode; > + unsigned int gpio_clk; > + unsigned int gpio_data; > + unsigned int write_enable;
Do not use the global GPIO number space, use GPIO descriptors.
Example: drivers/input/keyboard/gpio_keys.c
> +static int ps2_gpio_write(struct serio *serio, unsigned char val) > +{ > + struct ps2_gpio_data *drvdata = serio->port_data; > + > + drvdata->mode = PS2_MODE_TX; > + drvdata->tx_byte = val; > + /* Make sure ISR running on other CPU notice changes. */ > + barrier();
This seems overengineered, is this really needed?
If we have races like this, the error is likely elsewhere, and should be fixed in the GPIO driver MMIO access or so.
> + disable_irq_nosync(drvdata->irq); > + gpio_direction_output(drvdata->gpio_clk, 0);
No use GPIO descriptors please.
> + // dev_info(drvdata->dev, "recv bit %u: %u\n", cnt, data);
Delete comments or convert to dev_dbg()
> +static int of_ps2_gpio_get_props(struct device *dev, > + struct ps2_gpio_data *drvdata) > +{ > + if (of_gpio_count(dev->of_node) < 2) > + return -ENODEV; > + > + drvdata->gpio_data = of_get_gpio(dev->of_node, 0); > + drvdata->gpio_clk = of_get_gpio(dev->of_node, 1); > + > + if (drvdata->gpio_data == -EPROBE_DEFER || > + drvdata->gpio_clk == -EPROBE_DEFER) > + return -EPROBE_DEFER; > + > + if (!gpio_is_valid(drvdata->gpio_data) || > + !gpio_is_valid(drvdata->gpio_clk)) { > + dev_err(dev, "invalid GPIOs, data=%d, clk=%d\n", > + drvdata->gpio_data, drvdata->gpio_clk); > + return -ENODEV; > + }
With GPIO descriptors you should just gpiod_get(dev, "foo", FLAG); No need to poke around in the device tree like this.
Error checks and deferrals apply as usual though.
> + error = devm_gpio_request(dev, drvdata->gpio_clk, "ps2 clk"); > + if (error) { > + dev_err(dev, "failed to request gpio %u: %d", > + drvdata->gpio_clk, error); > + goto err_free_serio; > + } > + > + error = devm_gpio_request(dev, drvdata->gpio_data, "ps2 data"); > + if (error) { > + dev_err(dev, "failed to request gpio %u: %d", > + drvdata->gpio_data, error); > + goto err_free_serio; > + }
So devm_gpiod_get(...)
> + gpio_direction_input(drvdata->gpio_clk); > + gpio_direction_input(drvdata->gpio_data);
And incidentallt then you can just specify GPIOD_IN as flag and it will be set up for you.
Yours, Linus Walleij
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