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Date: Mon, 20 Dec 2021 12:19:00 +0100
From: Johan Hovold <johan@...nel.org>
To: Johan Hovold <johan@...nel.org>
Cc: Marc Ferland <ferlandm@...tus.ca>, linux-usb@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH 1/2] gnss: add USB support
Add a generic driver for GNSS receivers with a USB interface with two
bulk endpoints.
The driver currently assumes that the device protocol is NMEA (only) but
this can be generalised later as needed.
Signed-off-by: Johan Hovold <johan@...nel.org>
---
drivers/gnss/Kconfig | 11 +++
drivers/gnss/Makefile | 3 +
drivers/gnss/usb.c | 209 ++++++++++++++++++++++++++++++++++++++++++
3 files changed, 223 insertions(+)
create mode 100644 drivers/gnss/usb.c
diff --git a/drivers/gnss/Kconfig b/drivers/gnss/Kconfig
index bd12e3d57baa..d7fe265c2869 100644
--- a/drivers/gnss/Kconfig
+++ b/drivers/gnss/Kconfig
@@ -54,4 +54,15 @@ config GNSS_UBX_SERIAL
If unsure, say N.
+config GNSS_USB
+ tristate "USB GNSS receiver support"
+ depends on USB
+ help
+ Say Y here if you have a GNSS receiver which uses a USB interface.
+
+ To compile this driver as a module, choose M here: the module will
+ be called gnss-usb.
+
+ If unsure, say N.
+
endif # GNSS
diff --git a/drivers/gnss/Makefile b/drivers/gnss/Makefile
index 451f11401ecc..bb2cbada3435 100644
--- a/drivers/gnss/Makefile
+++ b/drivers/gnss/Makefile
@@ -17,3 +17,6 @@ gnss-sirf-y := sirf.o
obj-$(CONFIG_GNSS_UBX_SERIAL) += gnss-ubx.o
gnss-ubx-y := ubx.o
+
+obj-$(CONFIG_GNSS_USB) += gnss-usb.o
+gnss-usb-y := usb.o
diff --git a/drivers/gnss/usb.c b/drivers/gnss/usb.c
new file mode 100644
index 000000000000..5c0251034def
--- /dev/null
+++ b/drivers/gnss/usb.c
@@ -0,0 +1,209 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Generic USB GNSS receiver driver
+ *
+ * Copyright (C) 2021 Johan Hovold <johan@...nel.org>
+ */
+
+#include <linux/errno.h>
+#include <linux/gnss.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/usb.h>
+
+#define GNSS_USB_READ_BUF_LEN 512
+#define GNSS_USB_WRITE_TIMEOUT 1000
+
+static const struct usb_device_id gnss_usb_id_table[] = {
+ { }
+};
+MODULE_DEVICE_TABLE(usb, gnss_usb_id_table);
+
+struct gnss_usb {
+ struct usb_device *udev;
+ struct usb_interface *intf;
+ struct gnss_device *gdev;
+ struct urb *read_urb;
+ unsigned int write_pipe;
+};
+
+static void gnss_usb_rx_complete(struct urb *urb)
+{
+ struct gnss_usb *gusb = urb->context;
+ struct gnss_device *gdev = gusb->gdev;
+ int status = urb->status;
+ int len;
+ int ret;
+
+ switch (status) {
+ case 0:
+ break;
+ case -ENOENT:
+ case -ECONNRESET:
+ case -ESHUTDOWN:
+ dev_dbg(&gdev->dev, "urb stopped: %d\n", status);
+ return;
+ case -EPIPE:
+ dev_err(&gdev->dev, "urb stopped: %d\n", status);
+ return;
+ default:
+ dev_dbg(&gdev->dev, "nonzero urb status: %d\n", status);
+ goto resubmit;
+ }
+
+ len = urb->actual_length;
+ if (len == 0)
+ goto resubmit;
+
+ ret = gnss_insert_raw(gdev, urb->transfer_buffer, len);
+ if (ret < len)
+ dev_dbg(&gdev->dev, "dropped %d bytes\n", len - ret);
+resubmit:
+ ret = usb_submit_urb(urb, GFP_ATOMIC);
+ if (ret && ret != -EPERM && ret != -ENODEV)
+ dev_err(&gdev->dev, "failed to resubmit urb: %d\n", ret);
+}
+
+static int gnss_usb_open(struct gnss_device *gdev)
+{
+ struct gnss_usb *gusb = gnss_get_drvdata(gdev);
+ int ret;
+
+ ret = usb_submit_urb(gusb->read_urb, GFP_KERNEL);
+ if (ret) {
+ if (ret != -EPERM && ret != -ENODEV)
+ dev_err(&gdev->dev, "failed to submit urb: %d\n", ret);
+ return ret;
+ }
+
+ return 0;
+}
+
+static void gnss_usb_close(struct gnss_device *gdev)
+{
+ struct gnss_usb *gusb = gnss_get_drvdata(gdev);
+
+ usb_kill_urb(gusb->read_urb);
+}
+
+static int gnss_usb_write_raw(struct gnss_device *gdev,
+ const unsigned char *buf, size_t count)
+{
+ struct gnss_usb *gusb = gnss_get_drvdata(gdev);
+ void *tbuf;
+ int ret;
+
+ tbuf = kmemdup(buf, count, GFP_KERNEL);
+ if (!tbuf)
+ return -ENOMEM;
+
+ ret = usb_bulk_msg(gusb->udev, gusb->write_pipe, tbuf, count, NULL,
+ GNSS_USB_WRITE_TIMEOUT);
+ kfree(tbuf);
+ if (ret)
+ return ret;
+
+ return count;
+}
+
+static const struct gnss_operations gnss_usb_gnss_ops = {
+ .open = gnss_usb_open,
+ .close = gnss_usb_close,
+ .write_raw = gnss_usb_write_raw,
+};
+
+static int gnss_usb_probe(struct usb_interface *intf, const struct usb_device_id *id)
+{
+ struct usb_device *udev = interface_to_usbdev(intf);
+ struct usb_endpoint_descriptor *in, *out;
+ struct gnss_device *gdev;
+ struct gnss_usb *gusb;
+ struct urb *urb;
+ size_t buf_len;
+ void *buf;
+ int ret;
+
+ ret = usb_find_common_endpoints(intf->cur_altsetting, &in, &out, NULL,
+ NULL);
+ if (ret)
+ return ret;
+
+ gusb = kzalloc(sizeof(*gusb), GFP_KERNEL);
+ if (!gusb)
+ return -ENOMEM;
+
+ gdev = gnss_allocate_device(&intf->dev);
+ if (!gdev) {
+ ret = -ENOMEM;
+ goto err_free_gusb;
+ }
+
+ gdev->ops = &gnss_usb_gnss_ops;
+ gdev->type = GNSS_TYPE_NMEA;
+ gnss_set_drvdata(gdev, gusb);
+
+ urb = usb_alloc_urb(0, GFP_KERNEL);
+ if (!urb)
+ goto err_put_gdev;
+
+ buf_len = max(usb_endpoint_maxp(in), GNSS_USB_READ_BUF_LEN);
+
+ buf = kzalloc(buf_len, GFP_KERNEL);
+ if (!buf)
+ goto err_free_urb;
+
+ usb_fill_bulk_urb(urb, udev,
+ usb_rcvbulkpipe(udev, usb_endpoint_num(in)),
+ buf, buf_len, gnss_usb_rx_complete, gusb);
+
+ gusb->intf = intf;
+ gusb->udev = udev;
+ gusb->gdev = gdev;
+ gusb->read_urb = urb;
+ gusb->write_pipe = usb_sndbulkpipe(udev, usb_endpoint_num(out));
+
+ ret = gnss_register_device(gdev);
+ if (ret)
+ goto err_free_buf;
+
+ usb_set_intfdata(intf, gusb);
+
+ return 0;
+
+err_free_buf:
+ kfree(buf);
+err_free_urb:
+ usb_free_urb(urb);
+err_put_gdev:
+ gnss_put_device(gdev);
+err_free_gusb:
+ kfree(gusb);
+
+ return ret;
+}
+
+static void gnss_usb_disconnect(struct usb_interface *intf)
+{
+ struct gnss_usb *gusb = usb_get_intfdata(intf);
+
+ gnss_deregister_device(gusb->gdev);
+
+ kfree(gusb->read_urb->transfer_buffer);
+ usb_free_urb(gusb->read_urb);
+ gnss_put_device(gusb->gdev);
+ kfree(gusb);
+}
+
+static struct usb_driver gnss_usb_driver = {
+ .name = "gnss-usb",
+ .probe = gnss_usb_probe,
+ .disconnect = gnss_usb_disconnect,
+ .id_table = gnss_usb_id_table,
+};
+module_usb_driver(gnss_usb_driver);
+
+MODULE_AUTHOR("Johan Hovold <johan@...nel.org>");
+MODULE_DESCRIPTION("Generic USB GNSS receiver driver");
+MODULE_LICENSE("GPL v2");
--
2.32.0
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