| Message ID | 20240509102442.176958-1-jtornosm@redhat.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [v2] module: create weak dependecies | expand |
On Thu, May 09, 2024 at 12:24:40PM GMT, Jose Ignacio Tornos Martinez wrote: >It has been seen that for some network mac drivers (i.e. lan78xx) the >related module for the phy is loaded dynamically depending on the current >hardware. In this case, the associated phy is read using mdio bus and then >the associated phy module is loaded during runtime (kernel function >phy_request_driver_module). However, no software dependency is defined, so >the user tools will no be able to get this dependency. For example, if >dracut is used and the hardware is present, lan78xx will be included but no >phy module will be added, and in the next restart the device will not work >from boot because no related phy will be found during initramfs stage. > >In order to solve this, we could define a normal 'pre' software dependency >in lan78xx module with all the possible phy modules (there may be some), >but proceeding in that way, all the possible phy modules would be loaded >while only one is necessary. > >The idea is to create a new type of dependency, that we are going to call >'weak' to be used only by the user tools that need to detect this situation. >In that way, for example, dracut could check the 'weak' dependency of the >modules involved in order to install these dependencies in initramfs too. >That is, for the commented lan78xx module, defining the 'weak' dependency >with the possible phy modules list, only the necessary phy would be loaded >on demand keeping the same behavior, but all the possible phy modules would >be available from initramfs. I think it's important a note about backward compatibility. If a system doesn't have a new-enough depmod, it will basically not create the new weadep file and initrd generators won't be able to use that. Only downside is not being able to use the new feature, but it should still work as previously. > >The 'weak' dependency support has been included in kmod: >https://github.com/kmod-project/kmod/commit/05828b4a6e9327a63ef94df544a042b5e9ce4fe7 > >Signed-off-by: Jose Ignacio Tornos Martinez <jtornosm@redhat.com> >--- >V1 -> V2: >- Include reference to 'weak' dependency support in kmod. > > include/linux/module.h | 5 +++++ > 1 file changed, 5 insertions(+) > >diff --git a/include/linux/module.h b/include/linux/module.h >index 1153b0d99a80..231e710d8736 100644 >--- a/include/linux/module.h >+++ b/include/linux/module.h >@@ -173,6 +173,11 @@ extern void cleanup_module(void); > */ > #define MODULE_SOFTDEP(_softdep) MODULE_INFO(softdep, _softdep) > >+/* Weak module dependencies. See man modprobe.d for details. Documentation/process/coding-style.rst section 8 says to balance the /* and */, but up to Luis what he enforces in the module tree. Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com> Lucas De Marchi >+ * Example: MODULE_WEAKDEP("module-foo") >+ */ >+#define MODULE_WEAKDEP(_weakdep) MODULE_INFO(weakdep, _weakdep) >+ > /* > * MODULE_FILE is used for generating modules.builtin > * So, make it no-op when this is being built as a module >-- >2.44.0 >
> I think it's important a note about backward compatibility. If a system > doesn't have a new-enough depmod, it will basically not create the new > weadep file and initrd generators won't be able to use that. Only > downside is not being able to use the new feature, but it should still > work as previously. Ok, good, idea, I will send a new version of the patch with the note. Documentation/process/coding-style.rst section 8 says to balance the /* and */, but up to Luis what he enforces in the module tree. Ok, I will fix that too. Thanks Best regards José Ignacio
diff --git a/include/linux/module.h b/include/linux/module.h index 1153b0d99a80..231e710d8736 100644 --- a/include/linux/module.h +++ b/include/linux/module.h @@ -173,6 +173,11 @@ extern void cleanup_module(void); */ #define MODULE_SOFTDEP(_softdep) MODULE_INFO(softdep, _softdep) +/* Weak module dependencies. See man modprobe.d for details. + * Example: MODULE_WEAKDEP("module-foo") + */ +#define MODULE_WEAKDEP(_weakdep) MODULE_INFO(weakdep, _weakdep) + /* * MODULE_FILE is used for generating modules.builtin * So, make it no-op when this is being built as a module
It has been seen that for some network mac drivers (i.e. lan78xx) the related module for the phy is loaded dynamically depending on the current hardware. In this case, the associated phy is read using mdio bus and then the associated phy module is loaded during runtime (kernel function phy_request_driver_module). However, no software dependency is defined, so the user tools will no be able to get this dependency. For example, if dracut is used and the hardware is present, lan78xx will be included but no phy module will be added, and in the next restart the device will not work from boot because no related phy will be found during initramfs stage. In order to solve this, we could define a normal 'pre' software dependency in lan78xx module with all the possible phy modules (there may be some), but proceeding in that way, all the possible phy modules would be loaded while only one is necessary. The idea is to create a new type of dependency, that we are going to call 'weak' to be used only by the user tools that need to detect this situation. In that way, for example, dracut could check the 'weak' dependency of the modules involved in order to install these dependencies in initramfs too. That is, for the commented lan78xx module, defining the 'weak' dependency with the possible phy modules list, only the necessary phy would be loaded on demand keeping the same behavior, but all the possible phy modules would be available from initramfs. The 'weak' dependency support has been included in kmod: https://github.com/kmod-project/kmod/commit/05828b4a6e9327a63ef94df544a042b5e9ce4fe7 Signed-off-by: Jose Ignacio Tornos Martinez <jtornosm@redhat.com> --- V1 -> V2: - Include reference to 'weak' dependency support in kmod. include/linux/module.h | 5 +++++ 1 file changed, 5 insertions(+)