meta: classes-recipe: A class for simple Kernel modules

The module class provides what is needed to compile a Linux Kernel module
but since the Makefile is always the same for simple modules that have
their sources in one directory level, I thought of creating new class wrapper
to automatically prepare the Makefile.
Also, using variable flag feature, a recipe can provide multiple modules
and can be handled the same way as PACKAGECONFIG is used to enabled/disable
features.

Signed-off-by: Talel BELHAJSALEM <bhstalel@gmail.com>
---
 .../recipes-kernel/hello-mod/hello-mod_0.1.bb |  11 +-
 meta/classes-recipe/simple-module.bbclass     | 116 ++++++++++++++++++
 2 files changed, 120 insertions(+), 7 deletions(-)
 create mode 100644 meta/classes-recipe/simple-module.bbclass

On Fri, Oct 27, 2023 at 8:07 PM BELHADJ SALEM Talel <bhstalel@gmail.com> wrote:
>
> The module class provides what is needed to compile a Linux Kernel module
> but since the Makefile is always the same for simple modules that have
> their sources in one directory level, I thought of creating new class wrapper
> to automatically prepare the Makefile.
> Also, using variable flag feature, a recipe can provide multiple modules
> and can be handled the same way as PACKAGECONFIG is used to enabled/disable
> features.

I find this method of preparing a kernel module much harder to follow
(and debug).

So Richard is ok with the class, I have no objections, it may serve a class of
developers, but it isn't something I'd support as a first option.

But please, create a separate example for it, not modifying hello-world, we want
that simple and explicit example to persist.

Bruce

>
> Signed-off-by: Talel BELHAJSALEM <bhstalel@gmail.com>
> ---
>  .../recipes-kernel/hello-mod/hello-mod_0.1.bb |  11 +-
>  meta/classes-recipe/simple-module.bbclass     | 116 ++++++++++++++++++
>  2 files changed, 120 insertions(+), 7 deletions(-)
>  create mode 100644 meta/classes-recipe/simple-module.bbclass
>
> diff --git a/meta-skeleton/recipes-kernel/hello-mod/hello-mod_0.1.bb b/meta-skeleton/recipes-kernel/hello-mod/hello-mod_0.1.bb
> index a2fb212a68..f191b08be5 100644
> --- a/meta-skeleton/recipes-kernel/hello-mod/hello-mod_0.1.bb
> +++ b/meta-skeleton/recipes-kernel/hello-mod/hello-mod_0.1.bb
> @@ -3,16 +3,13 @@ DESCRIPTION = "${SUMMARY}"
>  LICENSE = "GPL-2.0-only"
>  LIC_FILES_CHKSUM = "file://COPYING;md5=12f884d2ae1ff87c09e5b7ccc2c4ca7e"
>
> -inherit module
> +inherit simple-module
>
> -SRC_URI = "file://Makefile \
> -           file://hello.c \
> +SRC_URI = "file://hello.c \
>             file://COPYING \
>            "
>
>  S = "${WORKDIR}"
>
> -# The inherit of module.bbclass will automatically name module packages with
> -# "kernel-module-" prefix as required by the oe-core build environment.
> -
> -RPROVIDES:${PN} += "kernel-module-hello"
> +MODULE_SRC = "hello"
> +MODULE_SRC[hello] = ""
> \ No newline at end of file
> diff --git a/meta/classes-recipe/simple-module.bbclass b/meta/classes-recipe/simple-module.bbclass
> new file mode 100644
> index 0000000000..a837dec848
> --- /dev/null
> +++ b/meta/classes-recipe/simple-module.bbclass
> @@ -0,0 +1,116 @@
> +#
> +# Copyright OpenEmbedded Contributors
> +#
> +# SPDX-License-Identifier: MIT
> +#
> +
> +# Class to generate Makefile for Linux Kernel modules
> +#
> +# The aim of this class is to provide a way to gain time
> +# when creating recipes for Linux Kernel modules
> +#
> +# Required variable:
> +#   MODULE_SRC
> +#
> +# This variable itself counts on flags to know what files
> +# to use for .ko generation and their .o dependencies
> +#
> +# Usage:
> +#   If you have the following module structure:
> +#       |-- module.c
> +#       |-- dep1.c
> +#       `-- dep2.c
> +#   then you set:
> +#   MODULE_SRC[module] = "dep1 dep2"
> +#
> +# This will generate:
> +#   obj-m += module.o
> +#   module-objs += dep1.o dep2.o
> +#
> +# This class supports multiple modules as well
> +# each module will be added to obj-m and if it has dependencies
> +# an -objs variable will be created.
> +#
> +# A module can be enabled or disabled by adding or removing
> +# the module name from MODULE_SRC
> +#
> +# Limitations:
> +#   - All modules source files should exist in the same folder level
> +
> +inherit module
> +
> +python do_prepare_makefile() {
> +
> +    if not (d.getVar('MODULE_SRC') or "").split():
> +        bb.warn("You inherited easy-module but did not set drivers in MODULE_SRC")
> +
> +    kernel_modules = (d.getVar('MODULE_SRC') or "").split()
> +
> +    if kernel_modules:
> +        kernel_modules_flags = d.getVarFlags('MODULE_SRC') or []
> +
> +        objs_data = {}
> +        for k_module in kernel_modules:
> +
> +            # Check if all enabled drivers have corresponding flag
> +            if not k_module in kernel_modules_flags:
> +                bb.fatal(f"Driver {k_module} is enabled but does not have a flag entry")
> +
> +            k_module_file = f"{k_module}.c"
> +            if not os.path.isfile(k_module_file):
> +                bb.fatal(f"Source file {k_module_file} is not found")
> +
> +            k_module_o = f"{k_module}.o"
> +            objs_data[k_module] = []
> +
> +            k_module_deps = (d.getVarFlag('MODULE_SRC', k_module) or "").split()
> +            for dep in k_module_deps:
> +                dep_file = f"{dep}.c"
> +                dep_o = f"{dep}.o"
> +
> +                if not os.path.isfile(dep_file):
> +                    bb.fatal(f"Dependency file {dep_file} for the {k_module_file} is not found")
> +
> +                objs_data[k_module].append(dep_o)
> +
> +        with open('Makefile', 'w') as mf:
> +            # Main modules
> +            mf.write(
> +                f"""
> +# This Makefile is generated automatically by easy-module class
> +obj-m += {' '.join([objm + '.o' for objm in objs_data.keys()])}
> +""")
> +
> +            # Modules dependencies
> +            for k_module, deps in objs_data.items():
> +                if deps:
> +                    mf.write(
> +                        f"""
> +{k_module}-objs += {' '.join([dep for dep in deps])}
> +""")
> +
> +            # Rest of Makefile
> +            mf.write(
> +                """
> +SRC := $(shell pwd)
> +
> +all:
> +\t$(MAKE) -C $(KERNEL_SRC) M=$(SRC)
> +
> +modules_install:
> +\t$(MAKE) -C $(KERNEL_SRC) M=$(SRC) modules_install
> +
> +clean:
> +\trm -f *.o *~ core .depend .*.cmd *.ko *.mod.c
> +\trm -f Module.markers Module.symvers modules.order
> +\trm -rf .tmp_versions Modules.symvers
> +""")
> +}
> +
> +RPROVIDES:${PN} += "kernel-module-${PN}"
> +
> +export SRC = "${B}"
> +
> +do_prepare_makefile[docs] = "Automate Makefile preparation for simple Kernel modules"
> +do_prepare_makefile[dirs] = "${B}"
> +addtask do_prepare_makefile before do_configure after do_patch
> \ No newline at end of file
> --
> 2.25.1
>
>
> -=-=-=-=-=-=-=-=-=-=-=-
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> -=-=-=-=-=-=-=-=-=-=-=-
>

Hello Bruce,

Thanks for the feedback, I agree that this is more suitable for developers
that want to integrate a quick driver
or a driver that has no Makefile, but I think adding the class for now and
then improvements or other ideas
can come.

I will remove the example as I included some examples in the class comment
itself.

Kind Regards
Talel

On Sat, Oct 28, 2023 at 1:35 PM Bruce Ashfield <bruce.ashfield@gmail.com>
wrote:

> On Fri, Oct 27, 2023 at 8:07 PM BELHADJ SALEM Talel <bhstalel@gmail.com>
> wrote:
> >
> > The module class provides what is needed to compile a Linux Kernel module
> > but since the Makefile is always the same for simple modules that have
> > their sources in one directory level, I thought of creating new class
> wrapper
> > to automatically prepare the Makefile.
> > Also, using variable flag feature, a recipe can provide multiple modules
> > and can be handled the same way as PACKAGECONFIG is used to
> enabled/disable
> > features.
>
> I find this method of preparing a kernel module much harder to follow
> (and debug).
>
> So Richard is ok with the class, I have no objections, it may serve a
> class of
> developers, but it isn't something I'd support as a first option.
>
> But please, create a separate example for it, not modifying hello-world,
> we want
> that simple and explicit example to persist.
>
> Bruce
>
> >
> > Signed-off-by: Talel BELHAJSALEM <bhstalel@gmail.com>
> > ---
> >  .../recipes-kernel/hello-mod/hello-mod_0.1.bb |  11 +-
> >  meta/classes-recipe/simple-module.bbclass     | 116 ++++++++++++++++++
> >  2 files changed, 120 insertions(+), 7 deletions(-)
> >  create mode 100644 meta/classes-recipe/simple-module.bbclass
> >
> > diff --git a/meta-skeleton/recipes-kernel/hello-mod/hello-mod_0.1.bb
> b/meta-skeleton/recipes-kernel/hello-mod/hello-mod_0.1.bb
> > index a2fb212a68..f191b08be5 100644
> > --- a/meta-skeleton/recipes-kernel/hello-mod/hello-mod_0.1.bb
> > +++ b/meta-skeleton/recipes-kernel/hello-mod/hello-mod_0.1.bb
> > @@ -3,16 +3,13 @@ DESCRIPTION = "${SUMMARY}"
> >  LICENSE = "GPL-2.0-only"
> >  LIC_FILES_CHKSUM = "file://COPYING;md5=12f884d2ae1ff87c09e5b7ccc2c4ca7e"
> >
> > -inherit module
> > +inherit simple-module
> >
> > -SRC_URI = "file://Makefile \
> > -           file://hello.c \
> > +SRC_URI = "file://hello.c \
> >             file://COPYING \
> >            "
> >
> >  S = "${WORKDIR}"
> >
> > -# The inherit of module.bbclass will automatically name module packages
> with
> > -# "kernel-module-" prefix as required by the oe-core build environment.
> > -
> > -RPROVIDES:${PN} += "kernel-module-hello"
> > +MODULE_SRC = "hello"
> > +MODULE_SRC[hello] = ""
> > \ No newline at end of file
> > diff --git a/meta/classes-recipe/simple-module.bbclass
> b/meta/classes-recipe/simple-module.bbclass
> > new file mode 100644
> > index 0000000000..a837dec848
> > --- /dev/null
> > +++ b/meta/classes-recipe/simple-module.bbclass
> > @@ -0,0 +1,116 @@
> > +#
> > +# Copyright OpenEmbedded Contributors
> > +#
> > +# SPDX-License-Identifier: MIT
> > +#
> > +
> > +# Class to generate Makefile for Linux Kernel modules
> > +#
> > +# The aim of this class is to provide a way to gain time
> > +# when creating recipes for Linux Kernel modules
> > +#
> > +# Required variable:
> > +#   MODULE_SRC
> > +#
> > +# This variable itself counts on flags to know what files
> > +# to use for .ko generation and their .o dependencies
> > +#
> > +# Usage:
> > +#   If you have the following module structure:
> > +#       |-- module.c
> > +#       |-- dep1.c
> > +#       `-- dep2.c
> > +#   then you set:
> > +#   MODULE_SRC[module] = "dep1 dep2"
> > +#
> > +# This will generate:
> > +#   obj-m += module.o
> > +#   module-objs += dep1.o dep2.o
> > +#
> > +# This class supports multiple modules as well
> > +# each module will be added to obj-m and if it has dependencies
> > +# an -objs variable will be created.
> > +#
> > +# A module can be enabled or disabled by adding or removing
> > +# the module name from MODULE_SRC
> > +#
> > +# Limitations:
> > +#   - All modules source files should exist in the same folder level
> > +
> > +inherit module
> > +
> > +python do_prepare_makefile() {
> > +
> > +    if not (d.getVar('MODULE_SRC') or "").split():
> > +        bb.warn("You inherited easy-module but did not set drivers in
> MODULE_SRC")
> > +
> > +    kernel_modules = (d.getVar('MODULE_SRC') or "").split()
> > +
> > +    if kernel_modules:
> > +        kernel_modules_flags = d.getVarFlags('MODULE_SRC') or []
> > +
> > +        objs_data = {}
> > +        for k_module in kernel_modules:
> > +
> > +            # Check if all enabled drivers have corresponding flag
> > +            if not k_module in kernel_modules_flags:
> > +                bb.fatal(f"Driver {k_module} is enabled but does not
> have a flag entry")
> > +
> > +            k_module_file = f"{k_module}.c"
> > +            if not os.path.isfile(k_module_file):
> > +                bb.fatal(f"Source file {k_module_file} is not found")
> > +
> > +            k_module_o = f"{k_module}.o"
> > +            objs_data[k_module] = []
> > +
> > +            k_module_deps = (d.getVarFlag('MODULE_SRC', k_module) or
> "").split()
> > +            for dep in k_module_deps:
> > +                dep_file = f"{dep}.c"
> > +                dep_o = f"{dep}.o"
> > +
> > +                if not os.path.isfile(dep_file):
> > +                    bb.fatal(f"Dependency file {dep_file} for the
> {k_module_file} is not found")
> > +
> > +                objs_data[k_module].append(dep_o)
> > +
> > +        with open('Makefile', 'w') as mf:
> > +            # Main modules
> > +            mf.write(
> > +                f"""
> > +# This Makefile is generated automatically by easy-module class
> > +obj-m += {' '.join([objm + '.o' for objm in objs_data.keys()])}
> > +""")
> > +
> > +            # Modules dependencies
> > +            for k_module, deps in objs_data.items():
> > +                if deps:
> > +                    mf.write(
> > +                        f"""
> > +{k_module}-objs += {' '.join([dep for dep in deps])}
> > +""")
> > +
> > +            # Rest of Makefile
> > +            mf.write(
> > +                """
> > +SRC := $(shell pwd)
> > +
> > +all:
> > +\t$(MAKE) -C $(KERNEL_SRC) M=$(SRC)
> > +
> > +modules_install:
> > +\t$(MAKE) -C $(KERNEL_SRC) M=$(SRC) modules_install
> > +
> > +clean:
> > +\trm -f *.o *~ core .depend .*.cmd *.ko *.mod.c
> > +\trm -f Module.markers Module.symvers modules.order
> > +\trm -rf .tmp_versions Modules.symvers
> > +""")
> > +}
> > +
> > +RPROVIDES:${PN} += "kernel-module-${PN}"
> > +
> > +export SRC = "${B}"
> > +
> > +do_prepare_makefile[docs] = "Automate Makefile preparation for simple
> Kernel modules"
> > +do_prepare_makefile[dirs] = "${B}"
> > +addtask do_prepare_makefile before do_configure after do_patch
> > \ No newline at end of file
> > --
> > 2.25.1
> >
> >
> > -=-=-=-=-=-=-=-=-=-=-=-
> > Links: You receive all messages sent to this group.
> > View/Reply Online (#189756):
> https://lists.openembedded.org/g/openembedded-core/message/189756
> > Mute This Topic: https://lists.openembedded.org/mt/102233042/1050810
> > Group Owner: openembedded-core+owner@lists.openembedded.org
> > Unsubscribe: https://lists.openembedded.org/g/openembedded-core/unsub [
> bruce.ashfield@gmail.com]
> > -=-=-=-=-=-=-=-=-=-=-=-
> >
>
>
> --
> - Thou shalt not follow the NULL pointer, for chaos and madness await
> thee at its end
> - "Use the force Harry" - Gandalf, Star Trek II
>

On Sat, 2023-10-28 at 08:35 -0400, Bruce Ashfield wrote:
> On Fri, Oct 27, 2023 at 8:07 PM BELHADJ SALEM Talel <bhstalel@gmail.com> wrote:
> > 
> > The module class provides what is needed to compile a Linux Kernel module
> > but since the Makefile is always the same for simple modules that have
> > their sources in one directory level, I thought of creating new class wrapper
> > to automatically prepare the Makefile.
> > Also, using variable flag feature, a recipe can provide multiple modules
> > and can be handled the same way as PACKAGECONFIG is used to enabled/disable
> > features.
> 
> I find this method of preparing a kernel module much harder to follow
> (and debug).
> 
> So Richard is ok with the class, I have no objections, it may serve a class of
> developers, but it isn't something I'd support as a first option.
> 
> But please, create a separate example for it, not modifying hello-world, we want
> that simple and explicit example to persist.

Richard isn't convinced.

In most cases a kernel module from a source repository would have some
form of makefile included with it. yes, if you're creating one from
scratch, this is helpful but in general you do create a makefile at
that point and are unlikely to want to keep auto-generating one.

As such I'm not convinced this class matches the siutation most people
wanting to build software would be in.

Cheers,

Richard

On Sat, Oct 28, 2023 at 9:51 AM Richard Purdie
<richard.purdie@linuxfoundation.org> wrote:
>
> On Sat, 2023-10-28 at 08:35 -0400, Bruce Ashfield wrote:
> > On Fri, Oct 27, 2023 at 8:07 PM BELHADJ SALEM Talel <bhstalel@gmail.com> wrote:
> > >
> > > The module class provides what is needed to compile a Linux Kernel module
> > > but since the Makefile is always the same for simple modules that have
> > > their sources in one directory level, I thought of creating new class wrapper
> > > to automatically prepare the Makefile.
> > > Also, using variable flag feature, a recipe can provide multiple modules
> > > and can be handled the same way as PACKAGECONFIG is used to enabled/disable
> > > features.
> >
> > I find this method of preparing a kernel module much harder to follow
> > (and debug).
> >
> > So Richard is ok with the class, I have no objections, it may serve a class of
> > developers, but it isn't something I'd support as a first option.
> >
> > But please, create a separate example for it, not modifying hello-world, we want
> > that simple and explicit example to persist.
>
> Richard isn't convinced.
>
> In most cases a kernel module from a source repository would have some
> form of makefile included with it. yes, if you're creating one from
> scratch, this is helpful but in general you do create a makefile at
> that point and are unlikely to want to keep auto-generating one.
>
> As such I'm not convinced this class matches the siutation most people
> wanting to build software would be in.

Everyone probably knows that I'm not in favour of generating pretty much
anything that can be clearer and more explicit. :)

I re-read my first reply, and it wasn't clear. It should have read "if
Richard is ok",
... those joining words are important.  What I meant to convey is that
I wouldn't
block something like this, if you were ok with it!

Bruce

>
> Cheers,
>
> Richard