[PATCH V6] gpio: Add virtio-gpio driver

From: Viresh Kumar
Date: Wed Aug 18 2021 - 07:14:43 EST

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This patch adds a new driver for Virtio based GPIO devices.

This allows a guest VM running Linux to access GPIO lines provided by
the host. It supports all basic operations, except interrupts for the
GPIO lines.

Based on the initial work posted by:
"Enrico Weigelt, metux IT consult" <lkml@xxxxxxxxx>.

Reviewed-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
Signed-off-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
---
Bartosz,

Can you please pick this up for 5.15, the specification is already merged now:

https://github.com/oasis-tcs/virtio-spec/blob/master/virtio-gpio.tex

I will follow up with the IRQ stuff separately.

V5->V6:
- Sent separately, without irq-support.
- Include the change for virtio_ids.h.

MAINTAINERS | 7 +
drivers/gpio/Kconfig | 9 +
drivers/gpio/Makefile | 1 +
drivers/gpio/gpio-virtio.c | 375 +++++++++++++++++++++++++++++++
include/uapi/linux/virtio_gpio.h | 47 ++++
include/uapi/linux/virtio_ids.h | 1 +
6 files changed, 440 insertions(+)
create mode 100644 drivers/gpio/gpio-virtio.c
create mode 100644 include/uapi/linux/virtio_gpio.h

diff --git a/MAINTAINERS b/MAINTAINERS
index a61f4f3b78a9..f632acd7d98c 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -19647,6 +19647,13 @@ F: Documentation/filesystems/virtiofs.rst
F: fs/fuse/virtio_fs.c
F: include/uapi/linux/virtio_fs.h

+VIRTIO GPIO DRIVER
+M: Enrico Weigelt, metux IT consult <info@xxxxxxxxx>
+M: Viresh Kumar <vireshk@xxxxxxxxxx>
+S: Maintained
+F: drivers/gpio/gpio-virtio.c
+F: include/uapi/linux/virtio_gpio.h
+
VIRTIO GPU DRIVER
M: David Airlie <airlied@xxxxxxxx>
M: Gerd Hoffmann <kraxel@xxxxxxxxxx>
diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index fab571016adf..e5993d6864fb 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -1669,6 +1669,15 @@ config GPIO_MOCKUP
tools/testing/selftests/gpio/gpio-mockup.sh. Reference the usage in
it.

+config GPIO_VIRTIO
+ tristate "VirtIO GPIO support"
+ depends on VIRTIO
+ help
+ Say Y here to enable guest support for virtio-based GPIO controllers.
+
+ These virtual GPIOs can be routed to real GPIOs or attached to
+ simulators on the host (like QEMU).
+
endmenu

endif
diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index 32a32659866a..e0301cfedd8d 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -165,6 +165,7 @@ obj-$(CONFIG_GPIO_UCB1400) += gpio-ucb1400.o
obj-$(CONFIG_GPIO_UNIPHIER) += gpio-uniphier.o
obj-$(CONFIG_GPIO_VF610) += gpio-vf610.o
obj-$(CONFIG_GPIO_VIPERBOARD) += gpio-viperboard.o
+obj-$(CONFIG_GPIO_VIRTIO) += gpio-virtio.o
obj-$(CONFIG_GPIO_VISCONTI) += gpio-visconti.o
obj-$(CONFIG_GPIO_VR41XX) += gpio-vr41xx.o
obj-$(CONFIG_GPIO_VX855) += gpio-vx855.o
diff --git a/drivers/gpio/gpio-virtio.c b/drivers/gpio/gpio-virtio.c
new file mode 100644
index 000000000000..4dc2d383508f
--- /dev/null
+++ b/drivers/gpio/gpio-virtio.c
@@ -0,0 +1,375 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * GPIO driver for virtio-based virtual GPIO controllers
+ *
+ * Copyright (C) 2021 metux IT consult
+ * Enrico Weigelt, metux IT consult <info@xxxxxxxxx>
+ *
+ * Copyright (C) 2021 Linaro.
+ * Viresh Kumar <viresh.kumar@xxxxxxxxxx>
+ */
+
+#include <linux/completion.h>
+#include <linux/err.h>
+#include <linux/gpio/driver.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/virtio_config.h>
+#include <uapi/linux/virtio_gpio.h>
+#include <uapi/linux/virtio_ids.h>
+
+struct virtio_gpio_line {
+ struct mutex lock; /* Protects line operation */
+ struct completion completion;
+ struct virtio_gpio_request req ____cacheline_aligned;
+ struct virtio_gpio_response res ____cacheline_aligned;
+ unsigned int rxlen;
+};
+
+struct virtio_gpio {
+ struct virtio_device *vdev;
+ struct mutex lock; /* Protects virtqueue operation */
+ struct gpio_chip gc;
+ struct virtio_gpio_config config;
+ struct virtio_gpio_line *lines;
+ struct virtqueue *request_vq;
+};
+
+static int _virtio_gpio_req(struct virtio_gpio *vgpio, u16 type, u16 gpio,
+ u8 txvalue, u8 *rxvalue, void *response, u32 rxlen)
+{
+ struct virtio_gpio_line *line = &vgpio->lines[gpio];
+ struct virtio_gpio_request *req = &line->req;
+ struct virtio_gpio_response *res = response;
+ struct scatterlist *sgs[2], req_sg, res_sg;
+ struct device *dev = &vgpio->vdev->dev;
+ int ret;
+
+ /*
+ * Prevent concurrent requests for the same line since we have
+ * pre-allocated request/response buffers for each GPIO line. Moreover
+ * Linux always accesses a GPIO line sequentially, so this locking shall
+ * always go through without any delays.
+ */
+ mutex_lock(&line->lock);
+
+ req->type = cpu_to_le16(type);
+ req->gpio = cpu_to_le16(gpio);
+ req->value = txvalue;
+
+ sg_init_one(&req_sg, req, sizeof(*req));
+ sg_init_one(&res_sg, res, rxlen);
+ sgs[0] = &req_sg;
+ sgs[1] = &res_sg;
+
+ line->rxlen = 0;
+ reinit_completion(&line->completion);
+
+ /*
+ * Virtqueue callers need to ensure they don't call its APIs with other
+ * virtqueue operations at the same time.
+ */
+ mutex_lock(&vgpio->lock);
+ ret = virtqueue_add_sgs(vgpio->request_vq, sgs, 1, 1, line, GFP_KERNEL);
+ if (ret) {
+ dev_err(dev, "failed to add request to vq\n");
+ mutex_unlock(&vgpio->lock);
+ goto out;
+ }
+
+ virtqueue_kick(vgpio->request_vq);
+ mutex_unlock(&vgpio->lock);
+
+ if (!wait_for_completion_timeout(&line->completion, HZ)) {
+ dev_err(dev, "GPIO operation timed out\n");
+ ret = -ETIMEDOUT;
+ goto out;
+ }
+
+ if (unlikely(res->status != VIRTIO_GPIO_STATUS_OK)) {
+ dev_err(dev, "GPIO request failed: %d\n", gpio);
+ ret = -EINVAL;
+ goto out;
+ }
+
+ if (unlikely(line->rxlen != rxlen)) {
+ dev_err(dev, "GPIO operation returned incorrect len (%u : %u)\n",
+ rxlen, line->rxlen);
+ ret = -EINVAL;
+ goto out;
+ }
+
+ if (rxvalue)
+ *rxvalue = res->value;
+
+out:
+ mutex_unlock(&line->lock);
+ return ret;
+}
+
+static int virtio_gpio_req(struct virtio_gpio *vgpio, u16 type, u16 gpio,
+ u8 txvalue, u8 *rxvalue)
+{
+ struct virtio_gpio_line *line = &vgpio->lines[gpio];
+ struct virtio_gpio_response *res = &line->res;
+
+ return _virtio_gpio_req(vgpio, type, gpio, txvalue, rxvalue, res,
+ sizeof(*res));
+}
+
+static void virtio_gpio_free(struct gpio_chip *gc, unsigned int gpio)
+{
+ struct virtio_gpio *vgpio = gpiochip_get_data(gc);
+
+ virtio_gpio_req(vgpio, VIRTIO_GPIO_MSG_SET_DIRECTION, gpio,
+ VIRTIO_GPIO_DIRECTION_NONE, NULL);
+}
+
+static int virtio_gpio_get_direction(struct gpio_chip *gc, unsigned int gpio)
+{
+ struct virtio_gpio *vgpio = gpiochip_get_data(gc);
+ u8 direction;
+ int ret;
+
+ ret = virtio_gpio_req(vgpio, VIRTIO_GPIO_MSG_GET_DIRECTION, gpio, 0,
+ &direction);
+ if (ret)
+ return ret;
+
+ switch (direction) {
+ case VIRTIO_GPIO_DIRECTION_IN:
+ return GPIO_LINE_DIRECTION_IN;
+ case VIRTIO_GPIO_DIRECTION_OUT:
+ return GPIO_LINE_DIRECTION_OUT;
+ default:
+ return -EINVAL;
+ }
+}
+
+static int virtio_gpio_direction_input(struct gpio_chip *gc, unsigned int gpio)
+{
+ struct virtio_gpio *vgpio = gpiochip_get_data(gc);
+
+ return virtio_gpio_req(vgpio, VIRTIO_GPIO_MSG_SET_DIRECTION, gpio,
+ VIRTIO_GPIO_DIRECTION_IN, NULL);
+}
+
+static int virtio_gpio_direction_output(struct gpio_chip *gc, unsigned int gpio,
+ int value)
+{
+ struct virtio_gpio *vgpio = gpiochip_get_data(gc);
+ int ret;
+
+ ret = virtio_gpio_req(vgpio, VIRTIO_GPIO_MSG_SET_VALUE, gpio, value, NULL);
+ if (ret)
+ return ret;
+
+ return virtio_gpio_req(vgpio, VIRTIO_GPIO_MSG_SET_DIRECTION, gpio,
+ VIRTIO_GPIO_DIRECTION_OUT, NULL);
+}
+
+static int virtio_gpio_get(struct gpio_chip *gc, unsigned int gpio)
+{
+ struct virtio_gpio *vgpio = gpiochip_get_data(gc);
+ u8 value;
+ int ret;
+
+ ret = virtio_gpio_req(vgpio, VIRTIO_GPIO_MSG_GET_VALUE, gpio, 0, &value);
+ return ret ? ret : value;
+}
+
+static void virtio_gpio_set(struct gpio_chip *gc, unsigned int gpio, int value)
+{
+ struct virtio_gpio *vgpio = gpiochip_get_data(gc);
+
+ virtio_gpio_req(vgpio, VIRTIO_GPIO_MSG_SET_VALUE, gpio, value, NULL);
+}
+
+static void virtio_gpio_request_vq(struct virtqueue *vq)
+{
+ struct virtio_gpio_line *line;
+ unsigned int len;
+
+ do {
+ line = virtqueue_get_buf(vq, &len);
+ if (!line)
+ return;
+
+ line->rxlen = len;
+ complete(&line->completion);
+ } while (1);
+}
+
+static void virtio_gpio_free_vqs(struct virtio_device *vdev)
+{
+ vdev->config->reset(vdev);
+ vdev->config->del_vqs(vdev);
+}
+
+static int virtio_gpio_alloc_vqs(struct virtio_gpio *vgpio,
+ struct virtio_device *vdev)
+{
+ const char * const names[] = { "requestq" };
+ vq_callback_t *cbs[] = {
+ virtio_gpio_request_vq,
+ };
+ struct virtqueue *vqs[1] = { NULL };
+ int ret;
+
+ ret = virtio_find_vqs(vdev, 1, vqs, cbs, names, NULL);
+ if (ret) {
+ dev_err(&vdev->dev, "failed to find vqs: %d\n", ret);
+ return ret;
+ }
+
+ if (!vqs[0]) {
+ dev_err(&vdev->dev, "failed to find requestq vq\n");
+ return -ENODEV;
+ }
+ vgpio->request_vq = vqs[0];
+
+ return 0;
+}
+
+static const char **virtio_gpio_get_names(struct virtio_gpio *vgpio)
+{
+ struct virtio_gpio_config *config = &vgpio->config;
+ struct virtio_gpio_response_get_names *res;
+ struct device *dev = &vgpio->vdev->dev;
+ u8 *gpio_names, *str;
+ const char **names;
+ int i, ret, len;
+
+ if (!config->gpio_names_size)
+ return NULL;
+
+ len = sizeof(*res) + config->gpio_names_size;
+ res = devm_kzalloc(dev, len, GFP_KERNEL);
+ if (!res)
+ return NULL;
+ gpio_names = res->value;
+
+ ret = _virtio_gpio_req(vgpio, VIRTIO_GPIO_MSG_GET_NAMES, 0, 0, NULL,
+ res, len);
+ if (ret) {
+ dev_err(dev, "Failed to get GPIO names: %d\n", ret);
+ return NULL;
+ }
+
+ names = devm_kcalloc(dev, config->ngpio, sizeof(names), GFP_KERNEL);
+ if (!names)
+ return NULL;
+
+ /* NULL terminate the string instead of checking it */
+ gpio_names[config->gpio_names_size - 1] = '\0';
+
+ for (i = 0, str = gpio_names; i < config->ngpio; i++) {
+ names[i] = str;
+ str += strlen(str) + 1; /* zero-length strings are allowed */
+
+ if (str > gpio_names + config->gpio_names_size) {
+ dev_err(dev, "gpio_names block is too short (%d)\n", i);
+ return NULL;
+ }
+ }
+
+ return names;
+}
+
+static int virtio_gpio_probe(struct virtio_device *vdev)
+{
+ struct virtio_gpio_config *config;
+ struct device *dev = &vdev->dev;
+ struct virtio_gpio *vgpio;
+ int ret, i;
+
+ vgpio = devm_kzalloc(dev, sizeof(*vgpio), GFP_KERNEL);
+ if (!vgpio)
+ return -ENOMEM;
+
+ config = &vgpio->config;
+
+ /* Read configuration */
+ virtio_cread_bytes(vdev, 0, config, sizeof(*config));
+ config->gpio_names_size = le32_to_cpu(config->gpio_names_size);
+ config->ngpio = le16_to_cpu(config->ngpio);
+ if (!config->ngpio) {
+ dev_err(dev, "Number of GPIOs can't be zero\n");
+ return -EINVAL;
+ }
+
+ vgpio->lines = devm_kcalloc(dev, config->ngpio, sizeof(*vgpio->lines), GFP_KERNEL);
+ if (!vgpio->lines)
+ return -ENOMEM;
+
+ for (i = 0; i < config->ngpio; i++) {
+ mutex_init(&vgpio->lines[i].lock);
+ init_completion(&vgpio->lines[i].completion);
+ }
+
+ mutex_init(&vgpio->lock);
+ vdev->priv = vgpio;
+
+ vgpio->vdev = vdev;
+ vgpio->gc.free = virtio_gpio_free;
+ vgpio->gc.get_direction = virtio_gpio_get_direction;
+ vgpio->gc.direction_input = virtio_gpio_direction_input;
+ vgpio->gc.direction_output = virtio_gpio_direction_output;
+ vgpio->gc.get = virtio_gpio_get;
+ vgpio->gc.set = virtio_gpio_set;
+ vgpio->gc.ngpio = config->ngpio;
+ vgpio->gc.base = -1; /* Allocate base dynamically */
+ vgpio->gc.label = dev_name(dev);
+ vgpio->gc.parent = dev;
+ vgpio->gc.owner = THIS_MODULE;
+ vgpio->gc.can_sleep = true;
+
+ ret = virtio_gpio_alloc_vqs(vgpio, vdev);
+ if (ret)
+ return ret;
+
+ /* Mark the device ready to perform operations from within probe() */
+ virtio_device_ready(vdev);
+
+ vgpio->gc.names = virtio_gpio_get_names(vgpio);
+
+ ret = gpiochip_add_data(&vgpio->gc, vgpio);
+ if (ret) {
+ virtio_gpio_free_vqs(vdev);
+ dev_err(dev, "Failed to add virtio-gpio controller\n");
+ }
+
+ return ret;
+}
+
+static void virtio_gpio_remove(struct virtio_device *vdev)
+{
+ struct virtio_gpio *vgpio = vdev->priv;
+
+ gpiochip_remove(&vgpio->gc);
+ virtio_gpio_free_vqs(vdev);
+}
+
+static const struct virtio_device_id id_table[] = {
+ { VIRTIO_ID_GPIO, VIRTIO_DEV_ANY_ID },
+ {},
+};
+MODULE_DEVICE_TABLE(virtio, id_table);
+
+static struct virtio_driver virtio_gpio_driver = {
+ .id_table = id_table,
+ .probe = virtio_gpio_probe,
+ .remove = virtio_gpio_remove,
+ .driver = {
+ .name = KBUILD_MODNAME,
+ .owner = THIS_MODULE,
+ },
+};
+module_virtio_driver(virtio_gpio_driver);
+
+MODULE_AUTHOR("Enrico Weigelt, metux IT consult <info@xxxxxxxxx>");
+MODULE_AUTHOR("Viresh Kumar <viresh.kumar@xxxxxxxxxx>");
+MODULE_DESCRIPTION("VirtIO GPIO driver");
+MODULE_LICENSE("GPL");
diff --git a/include/uapi/linux/virtio_gpio.h b/include/uapi/linux/virtio_gpio.h
new file mode 100644
index 000000000000..844574acf095
--- /dev/null
+++ b/include/uapi/linux/virtio_gpio.h
@@ -0,0 +1,47 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+
+#ifndef _LINUX_VIRTIO_GPIO_H
+#define _LINUX_VIRTIO_GPIO_H
+
+#include <linux/types.h>
+
+/* Virtio GPIO request types */
+#define VIRTIO_GPIO_MSG_GET_NAMES 0x0001
+#define VIRTIO_GPIO_MSG_GET_DIRECTION 0x0002
+#define VIRTIO_GPIO_MSG_SET_DIRECTION 0x0003
+#define VIRTIO_GPIO_MSG_GET_VALUE 0x0004
+#define VIRTIO_GPIO_MSG_SET_VALUE 0x0005
+
+/* Possible values of the status field */
+#define VIRTIO_GPIO_STATUS_OK 0x0
+#define VIRTIO_GPIO_STATUS_ERR 0x1
+
+/* Direction types */
+#define VIRTIO_GPIO_DIRECTION_NONE 0x00
+#define VIRTIO_GPIO_DIRECTION_OUT 0x01
+#define VIRTIO_GPIO_DIRECTION_IN 0x02
+
+struct virtio_gpio_config {
+ __u16 ngpio;
+ __u8 padding[2];
+ __u32 gpio_names_size;
+} __packed;
+
+/* Virtio GPIO Request / Response */
+struct virtio_gpio_request {
+ __u16 type;
+ __u16 gpio;
+ __u32 value;
+};
+
+struct virtio_gpio_response {
+ __u8 status;
+ __u8 value;
+};
+
+struct virtio_gpio_response_get_names {
+ __u8 status;
+ __u8 value[];
+};
+
+#endif /* _LINUX_VIRTIO_GPIO_H */
diff --git a/include/uapi/linux/virtio_ids.h b/include/uapi/linux/virtio_ids.h
index 70a8057ad4bb..e04fa2bfc0eb 100644
--- a/include/uapi/linux/virtio_ids.h
+++ b/include/uapi/linux/virtio_ids.h
@@ -56,6 +56,7 @@
#define VIRTIO_ID_PMEM 27 /* virtio pmem */
#define VIRTIO_ID_MAC80211_HWSIM 29 /* virtio mac80211-hwsim */
#define VIRTIO_ID_BT 40 /* virtio bluetooth */
+#define VIRTIO_ID_GPIO 41 /* virtio gpio */

/*
* Virtio Transitional IDs
--
2.31.1.272.g89b43f80a514

Next message: Christian Gmeiner: "[PATCH] arm64: dts: ti: k3-am64-mcu: Add pinctrl"
Previous message: Miquel Raynal: "[PATCH 11/16] iio: adc: max1027: Separate the IRQ handler from the read logic"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]