net: make NET a menuconfig (and downgrade NO_NET to a simple config)

This will allow a bunch of simplifications across the code base.
Disabling NET is the equivalent of today's NO_NET choice. This means
that if NET is enabled, either the legacy or lwIP stack is necessarily
selected, which allows us to simplify if NET_LEGACY || NET_LWIP into
if NET in a later commit.

Config fragments - or defconfigs including other defconfigs - setting
the network stack (NET_LEGACY or NET_LWIP) must also set NET (or unset
NO_NET) if the config they apply to - or the included defconfigs -
unsets NET (or selects NO_NET) as otherwise the NET_LEGACY and NET_LWIP
symbols are unreachable. This is the case for the two defconfig modified
in this commit.

NO_NET is now a convenience symbol which hides NET entirely to avoid
modifying many defconfigs. If one selected NO_NET to disable the
networking stack in the past, this will still work for now. Technically,
we should be using the "transitional" Kconfig attribute but that is only
available since Kconfig from Linux kernel v6.18 and we're on 6.1 right
now.

Note that this moves CONFIG_SYS_RX_ETH_BUFFER from under the Network
menu back into the main menu as it seems like it needs to be defined
even when there's no need for NET support at all and menuconfig option
doesn't work the same way as a menu.

Signed-off-by: Quentin Schulz <[email protected]>
Reviewed-by: Simon Glass <[email protected]>
Acked-by: Heinrich Schuchardt <[email protected]>
Reviewed-by: Peter Robinson <[email protected]>
Reviewed-by: Tom Rini <[email protected]>

3 files changed, 14 insertions, 13 deletions

diff --git a/configs/am62px_evm_r5_ethboot_defconfig b/configs/am62px_evm_r5_ethboot_defconfig
index 8baec9d43ff..df49324b25a 100644
--- a/configs/am62px_evm_r5_ethboot_defconfig
+++ b/configs/am62px_evm_r5_ethboot_defconfig
@@ -5,7 +5,7 @@ CONFIG_ARCH_K3=y
 CONFIG_SOC_K3_AM62P5=y
 CONFIG_TARGET_AM62P5_R5_EVM=y
 CONFIG_DEFAULT_DEVICE_TREE="k3-am62p5-r5-sk"
-CONFIG_NET_LEGACY=y
+# CONFIG_NO_NET is not set
 CONFIG_SPL_BOARD_INIT=y
 CONFIG_SPL_DMA=y
 CONFIG_SPL_ENV_SUPPORT=y
diff --git a/configs/j722s_evm_r5_ethboot_defconfig b/configs/j722s_evm_r5_ethboot_defconfig
index e4682edb455..cc71f913d3c 100644
--- a/configs/j722s_evm_r5_ethboot_defconfig
+++ b/configs/j722s_evm_r5_ethboot_defconfig
@@ -5,7 +5,7 @@ CONFIG_ARCH_K3=y
 CONFIG_SOC_K3_J722S=y
 CONFIG_TARGET_J722S_R5_EVM=y
 CONFIG_DEFAULT_DEVICE_TREE="k3-j722s-r5-evm"
-CONFIG_NET_LEGACY=y
+# CONFIG_NO_NET is not set
 CONFIG_SPL_DRIVERS_MISC=y
 CONFIG_SPL_BOARD_INIT=y
 CONFIG_SPL_DMA=y
diff --git a/net/Kconfig b/net/Kconfig
index 89d949b5f2c..e712a0dd2ac 100644
--- a/net/Kconfig
+++ b/net/Kconfig
@@ -2,17 +2,22 @@
 # Network configuration
 #
 
-menu "Networking"
+config NO_NET
+	bool "Disable networking"
+	help
+	  Transitional variable. Equivalent to setting NET=n.
+
+menuconfig NET
+	bool "Networking"
+	depends on !NO_NET
+	default y
+
+if NET
 
 choice
 	prompt "Networking stack"
 	default NET_LEGACY
 
-config NO_NET
-	bool "No networking support"
-	help
-	  Do not include networking support
-
 config NET_LEGACY
 	bool "Legacy U-Boot networking stack"
 	select NETDEVICES
@@ -231,8 +236,6 @@ endif   # if NET_LEGACY
 
 source "net/lwip/Kconfig"
 
-if NET_LEGACY || NET_LWIP
-
 config BOOTDEV_ETH
 	bool "Enable bootdev for ethernet"
 	depends on BOOTSTD
@@ -276,7 +279,7 @@ config TFTP_BLOCKSIZE
 	  almost-MTU block sizes.
 	  You can also activate CONFIG_IP_DEFRAG to set a larger block.
 
-endif   # if NET_LEGACY || NET_LWIP
+endif   # if NET
 
 config SYS_RX_ETH_BUFFER
         int "Number of receive packet buffers"
@@ -286,5 +289,3 @@ config SYS_RX_ETH_BUFFER
           controllers it is recommended to set this value to 8 or even higher,
           since all buffers can be full shortly after enabling the interface on
           high Ethernet traffic.
-
-endmenu