ice: use GNSS subsystem instead of TTY

Previously support for GNSS was implemented as a TTY driver, it allowed
to access GNSS receiver on /dev/ttyGNSS_<bus><func>.

Use generic GNSS subsystem API instead of implementing own TTY driver.
The receiver is accessible on /dev/gnss<id>. In case of multiple receivers
in the OS, correct device can be found by enumerating either:
- /sys/class/net/<eth port>/device/gnss/
- /sys/class/gnss/gnss<id>/device/

Using GNSS subsystem is superior to implementing own TTY driver, as the
GNSS subsystem was designed solely for this purpose. It also implements
TTY driver but in a common and defined way.

From user perspective, there is no difference in communicating with a
device, except new path to the device shall be used. The device will
provide same information to the userspace as the old one, and can be used
in the same way, i.e.:
old # gpsmon /dev/ttyGNSS_2100_0
new # gpsmon /dev/gnss0
There is no other impact on userspace tools.

User expecting onboard GNSS receiver support is required to enable
CONFIG_GNSS=y/m in kernel config.
Reviewed-by: Alexander Lobakin <alexandr.lobakin@intel.com>
Signed-off-by: Karol Kolacinski <karol.kolacinski@intel.com>
Signed-off-by: Michal Michalik <michal.michalik@intel.com>
Signed-off-by: Arkadiusz Kubalewski <arkadiusz.kubalewski@intel.com>
Tested-by: Gurucharan G <gurucharanx.g@intel.com> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/networking/device_drivers/ethernet/intel/ice.rst

@@ -901,15 +901,17 @@ To enable/disable UDP Segmentation Offload, issue the following command::
 
   # ethtool -K <ethX> tx-udp-segmentation [off|on]
 
+
 GNSS module
 -----------
-Allows user to read messages from the GNSS module and write supported commands.
-If the module is physically present, driver creates 2 TTYs for each supported
-device in /dev, ttyGNSS_<device>:<function>_0 and _1. First one (_0) is RW and
-the second one is RO.
-The protocol of write commands is dependent on the GNSS module as the driver
-writes raw bytes from the TTY to the GNSS i2c. Please refer to the module
-documentation for details.
+Requires kernel compiled with CONFIG_GNSS=y or CONFIG_GNSS=m.
+Allows user to read messages from the GNSS hardware module and write supported
+commands. If the module is physically present, a GNSS device is spawned:
+``/dev/gnss<id>``.
+The protocol of write command is dependent on the GNSS hardware module as the
+driver writes raw bytes by the GNSS object to the receiver through i2c. Please
+refer to the hardware GNSS module documentation for configuration details.
+
 
 Performance Optimization
 ========================

drivers/net/ethernet/intel/Kconfig

@@ -337,6 +337,9 @@ config ICE_HWTS
 	  the PTP clock driver precise cross-timestamp ioctl
 	  (PTP_SYS_OFFSET_PRECISE).
 
+config ICE_GNSS
+	def_bool GNSS = y || GNSS = ICE
+
 config FM10K
 	tristate "Intel(R) FM10000 Ethernet Switch Host Interface Support"
 	default n

drivers/net/ethernet/intel/ice/Makefile

@@ -43,8 +43,8 @@ ice-$(CONFIG_PCI_IOV) +=	\
 	ice_vf_vsi_vlan_ops.o	\
 	ice_vf_lib.o
 ice-$(CONFIG_PTP_1588_CLOCK) += ice_ptp.o ice_ptp_hw.o
-ice-$(CONFIG_TTY) += ice_gnss.o
 ice-$(CONFIG_DCB) += ice_dcb.o ice_dcb_nl.o ice_dcb_lib.o
 ice-$(CONFIG_RFS_ACCEL) += ice_arfs.o
 ice-$(CONFIG_XDP_SOCKETS) += ice_xsk.o
 ice-$(CONFIG_ICE_SWITCHDEV) += ice_eswitch.o
+ice-$(CONFIG_ICE_GNSS) += ice_gnss.o

drivers/net/ethernet/intel/ice/ice.h

@@ -39,6 +39,7 @@
 #include <linux/avf/virtchnl.h>
 #include <linux/cpu_rmap.h>
 #include <linux/dim.h>
+#include <linux/gnss.h>
 #include <net/pkt_cls.h>
 #include <net/tc_act/tc_mirred.h>
 #include <net/tc_act/tc_gact.h>
@@ -565,9 +566,8 @@ struct ice_pf {
 	struct mutex adev_mutex;	/* lock to protect aux device access */
 	u32 msg_enable;
 	struct ice_ptp ptp;
-	struct tty_driver *ice_gnss_tty_driver;
-	struct tty_port *gnss_tty_port[ICE_GNSS_TTY_MINOR_DEVICES];
-	struct gnss_serial *gnss_serial[ICE_GNSS_TTY_MINOR_DEVICES];
+	struct gnss_serial *gnss_serial;
+	struct gnss_device *gnss_dev;
 	u16 num_rdma_msix;		/* Total MSIX vectors for RDMA driver */
 	u16 rdma_base_vector;
 

drivers/net/ethernet/intel/ice/ice_gnss.h

@@ -4,15 +4,8 @@
 #ifndef _ICE_GNSS_H_
 #define _ICE_GNSS_H_
 
-#include <linux/tty.h>
-#include <linux/tty_flip.h>
-
 #define ICE_E810T_GNSS_I2C_BUS		0x2
 #define ICE_GNSS_TIMER_DELAY_TIME	(HZ / 10) /* 0.1 second per message */
-/* Create 2 minor devices, both using the same GNSS module. First one is RW,
- * second one RO.
- */
-#define ICE_GNSS_TTY_MINOR_DEVICES	2
 #define ICE_GNSS_TTY_WRITE_BUF		250
 #define ICE_MAX_I2C_DATA_SIZE		FIELD_MAX(ICE_AQC_I2C_DATA_SIZE_M)
 #define ICE_MAX_I2C_WRITE_BYTES		4
@@ -36,13 +29,9 @@ struct gnss_write_buf {
 	unsigned char *buf;
 };
 
-
 /**
  * struct gnss_serial - data used to initialize GNSS TTY port
  * @back: back pointer to PF
- * @tty: pointer to the tty for this device
- * @open_count: number of times this port has been opened
- * @gnss_mutex: gnss_mutex used to protect GNSS serial operations
  * @kworker: kwork thread for handling periodic work
  * @read_work: read_work function for handling GNSS reads
  * @write_work: write_work function for handling GNSS writes
@@ -50,16 +39,13 @@ struct gnss_write_buf {
  */
 struct gnss_serial {
 	struct ice_pf *back;
-	struct tty_struct *tty;
-	int open_count;
-	struct mutex gnss_mutex; /* protects GNSS serial structure */
 	struct kthread_worker *kworker;
 	struct kthread_delayed_work read_work;
 	struct kthread_work write_work;
 	struct list_head queue;
 };
 
-#if IS_ENABLED(CONFIG_TTY)
+#if IS_ENABLED(CONFIG_ICE_GNSS)
 void ice_gnss_init(struct ice_pf *pf);
 void ice_gnss_exit(struct ice_pf *pf);
 bool ice_gnss_is_gps_present(struct ice_hw *hw);
@@ -70,5 +56,5 @@ static inline bool ice_gnss_is_gps_present(struct ice_hw *hw)
 {
 	return false;
 }
-#endif /* IS_ENABLED(CONFIG_TTY) */
+#endif /* IS_ENABLED(CONFIG_ICE_GNSS) */
 #endif /* _ICE_GNSS_H_ */