ice: use GNSS subsystem instead of TTY

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2111048

Upstream commit(s):
commit c7ef822
Author: Arkadiusz Kubalewski <arkadiusz.kubalewski@intel.com>
Date:   Wed Jan 18 16:58:36 2023 -0800

    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>

Signed-off-by: Petr Oros <poros@redhat.com>

Author: orosp

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

@@ -42,8 +42,8 @@ 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>
@@ -543,9 +544,8 @@ 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;