gnss: add receiver type support

Add a "type" device attribute and a "GNSS_TYPE" uevent variable which
can be used to determine the type of a GNSS receiver. The currently
identified types reflect the protocol(s) supported by a receiver:

	"NMEA"	NMEA 0183
	"SiRF"	SiRF Binary
	"UBX"	UBX

Note that both SiRF and UBX type receivers typically support a subset of
NMEA 0183 with vendor extensions (e.g. to allow switching to the vendor
protocol).

Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

6 files changed, 77 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-class-gnss b/Documentation/ABI/testing/sysfs-class-gnss
new file mode 100644
index 000000000000..2467b6900eae
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-class-gnss
@@ -0,0 +1,15 @@
+What:           /sys/class/gnss/gnssN/type
+Date:           May 2018
+KernelVersion:  4.18
+Contact:        Johan Hovold <johan@kernel.org>
+Description:
+                The GNSS receiver type. The currently identified types reflect
+                the protocol(s) supported by the receiver:
+
+                        "NMEA"          NMEA 0183
+                        "SiRF"          SiRF Binary
+                        "UBX"           UBX
+
+                Note that also non-"NMEA" type receivers typically support a
+                subset of NMEA 0183 with vendor extensions (e.g. to allow
+                switching to a vendor protocol).
diff --git a/MAINTAINERS b/MAINTAINERS
index f980c6186094..e01d220a6f05 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -6041,6 +6041,7 @@ F:	include/uapi/linux/gigaset_dev.h
 GNSS SUBSYSTEM
 M:      Johan Hovold <johan@kernel.org>
 S:      Maintained
+F:      Documentation/ABI/testing/sysfs-class-gnss
 F:      Documentation/devicetree/bindings/gnss/
 F:      drivers/gnss/
 F:      include/linux/gnss.h
diff --git a/drivers/gnss/core.c b/drivers/gnss/core.c
index 307894ca2725..f30ef8338b3a 100644
--- a/drivers/gnss/core.c
+++ b/drivers/gnss/core.c
@@ -330,6 +330,52 @@ int gnss_insert_raw(struct gnss_device *gdev, const unsigned char *buf,
 }
 EXPORT_SYMBOL_GPL(gnss_insert_raw);
 
+static const char * const gnss_type_names[GNSS_TYPE_COUNT] = {
+        [GNSS_TYPE_NMEA]        = "NMEA",
+        [GNSS_TYPE_SIRF]        = "SiRF",
+        [GNSS_TYPE_UBX]         = "UBX",
+};
+
+static const char *gnss_type_name(struct gnss_device *gdev)
+{
+        const char *name = NULL;
+
+        if (gdev->type < GNSS_TYPE_COUNT)
+                name = gnss_type_names[gdev->type];
+
+        if (!name)
+                dev_WARN(&gdev->dev, "type name not defined\n");
+
+        return name;
+}
+
+static ssize_t type_show(struct device *dev, struct device_attribute *attr,
+                                char *buf)
+{
+        struct gnss_device *gdev = to_gnss_device(dev);
+
+        return sprintf(buf, "%s\n", gnss_type_name(gdev));
+}
+static DEVICE_ATTR_RO(type);
+
+static struct attribute *gnss_attrs[] = {
+        &dev_attr_type.attr,
+        NULL,
+};
+ATTRIBUTE_GROUPS(gnss);
+
+static int gnss_uevent(struct device *dev, struct kobj_uevent_env *env)
+{
+        struct gnss_device *gdev = to_gnss_device(dev);
+        int ret;
+
+        ret = add_uevent_var(env, "GNSS_TYPE=%s", gnss_type_name(gdev));
+        if (ret)
+                return ret;
+
+        return 0;
+}
+
 static int __init gnss_module_init(void)
 {
         int ret;
@@ -347,6 +393,9 @@ static int __init gnss_module_init(void)
                 goto err_unregister_chrdev;
         }
 
+        gnss_class->dev_groups = gnss_groups;
+        gnss_class->dev_uevent = gnss_uevent;
+
         pr_info("GNSS driver registered with major %d\n", MAJOR(gnss_first));
 
         return 0;
diff --git a/drivers/gnss/sirf.c b/drivers/gnss/sirf.c
index 5fb0f730db48..79cb98950013 100644
--- a/drivers/gnss/sirf.c
+++ b/drivers/gnss/sirf.c
@@ -267,6 +267,7 @@ static int sirf_probe(struct serdev_device *serdev)
         if (!gdev)
                 return -ENOMEM;
 
+        gdev->type = GNSS_TYPE_SIRF;
         gdev->ops = &sirf_gnss_ops;
         gnss_set_drvdata(gdev, data);
 
diff --git a/drivers/gnss/ubx.c b/drivers/gnss/ubx.c
index ecddfb362a6f..902b6854b7db 100644
--- a/drivers/gnss/ubx.c
+++ b/drivers/gnss/ubx.c
@@ -77,6 +77,8 @@ static int ubx_probe(struct serdev_device *serdev)
 
         gserial->ops = &ubx_gserial_ops;
 
+        gserial->gdev->type = GNSS_TYPE_UBX;
+
         data = gnss_serial_get_drvdata(gserial);
 
         data->vcc = devm_regulator_get(&serdev->dev, "vcc");
diff --git a/include/linux/gnss.h b/include/linux/gnss.h
index e26aeac1e0e2..43546977098c 100644
--- a/include/linux/gnss.h
+++ b/include/linux/gnss.h
@@ -18,6 +18,14 @@
 
 struct gnss_device;
 
+enum gnss_type {
+        GNSS_TYPE_NMEA = 0,
+        GNSS_TYPE_SIRF,
+        GNSS_TYPE_UBX,
+
+        GNSS_TYPE_COUNT
+};
+
 struct gnss_operations {
         int (*open)(struct gnss_device *gdev);
         void (*close)(struct gnss_device *gdev);
@@ -30,6 +38,7 @@ struct gnss_device {
         struct cdev cdev;
         int id;
 
+        enum gnss_type type;
         unsigned long flags;
 
         struct rw_semaphore rwsem;