[PATCH v2 1/3] kni: flag deprecated status at build time

[Bruce Richardson <bruce.richardson@intel.com>]

To ensure all users are aware of KNI's deprecated status at build time
we can take the following actions:

1. disable the library by default. It can be re-enabled by setting
   disabled_libs to the empty string (or other string not including
   'kni')

2. add support for a list of deprecated libs to the lib/meson.build file
   so the error message for KNI being disabled includes the fact that it
   is a deprecated library.

3. for the dependent NIC driver, drivers/net/kni, modify its disabled
   message to also reference the fact that KNI is disabled.

NOTE: This is part of the deprecation process for KNI agreed by the DPDK
technical board.[1]

[1] http://mails.dpdk.org/archives/dev/2022-June/243596.html

Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
---
V2: correct dpdk_conf lookup key to RTE_LIB_KNI
---
 doc/guides/prog_guide/kernel_nic_interface.rst | 4 ++++
 drivers/net/kni/meson.build                    | 5 +++++
 lib/meson.build                                | 7 +++++++
 meson_options.txt                              | 2 +-
 4 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/doc/guides/prog_guide/kernel_nic_interface.rst b/doc/guides/prog_guide/kernel_nic_interface.rst
index 03b5bca958..6a564f61ca 100644
--- a/doc/guides/prog_guide/kernel_nic_interface.rst
+++ b/doc/guides/prog_guide/kernel_nic_interface.rst
@@ -14,6 +14,10 @@ Kernel NIC Interface
    For an alternative to KNI, that does not require any out-of-tree Linux kernel modules,
    or a custom library, see :ref:`virtio_user_as_exception_path`.

+.. note::
+
+   KNI is disabled by default in the DPDK build.
+   To re-enable the library, remove 'kni' from the "disable_libs" meson option when configuring a build.

 The DPDK Kernel NIC Interface (KNI) allows userspace applications access to the Linux* control plane.

diff --git a/drivers/net/kni/meson.build b/drivers/net/kni/meson.build
index 2acc989694..6289aa6cc3 100644
--- a/drivers/net/kni/meson.build
+++ b/drivers/net/kni/meson.build
@@ -6,6 +6,11 @@ if is_windows
     reason = 'not supported on Windows'
     subdir_done()
 endif
+if not dpdk_conf.has('RTE_LIB_KNI')
+    build = false
+    reason = 'needs deprecated lib, "kni"'
+    subdir_done()
+endif

 deps += 'kni'
 sources = files('rte_eth_kni.c')
diff --git a/lib/meson.build b/lib/meson.build
index c648f7d800..264a1671df 100644
--- a/lib/meson.build
+++ b/lib/meson.build
@@ -85,6 +85,7 @@ optional_libs = [
         'vhost',
 ]

+deprecated_libs = ['kni']
 disabled_libs = []
 opt_disabled_libs = run_command(list_dir_globs, get_option('disable_libs'),
         check: true).stdout().split()
@@ -133,7 +134,13 @@ foreach l:libraries
     if disabled_libs.contains(l)
         build = false
         reason = 'explicitly disabled via build config'
+        if deprecated_libs.contains(l)
+            reason += ' (deprecated lib)'
+        endif
     else
+        if deprecated_libs.contains(l)
+            warning('Enabling deprecated library, "@0@"'.format(l))
+        endif
         subdir(l)
     endif
     if name != l
diff --git a/meson_options.txt b/meson_options.txt
index 8640f599ae..39af78787c 100644
--- a/meson_options.txt
+++ b/meson_options.txt
@@ -8,7 +8,7 @@ option('developer_mode', type: 'feature', description:
        'turn on additional build checks relevant for DPDK developers')
 option('disable_drivers', type: 'string', value: '', description:
        'Comma-separated list of drivers to explicitly disable.')
-option('disable_libs', type: 'string', value: '', description:
+option('disable_libs', type: 'string', value: 'kni', description:
        'Comma-separated list of libraries to explicitly disable. [NOTE: not all libs can be disabled]')
 option('drivers_install_subdir', type: 'string', value: 'dpdk/pmds-<VERSION>', description:
        'Subdirectory of libdir where to install PMDs. Defaults to using a versioned subdirectory.')
--
2.34.1