What is the minimal set of firmware files I need for my hardware?

What is the minimal set of firmware files I need for my hardware?

[Doron Behar]

I hope this question fits to this List.

Today I learned that my distro's `linux-unfree-firmware` package is 491
Mb in size. I'm pretty sure my hardware doesn't need all of these files.
Maybe different Linux distros call this package differently, but I'm talking
about the firmware files that come from:
https://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git/

I think I can reduce this disk usage if I'll only know what files
I can exclude from there.

Is there any official documentation, that states exactly what files from
That git repo are needed per device / computer model? Perhaps the official
documentation of my Computer's hardware will state that? There's a Linux
from scratch webpage[1] that gives some info for popular hardware, but I'm
wondering if there's a bit more "official" information available
somewhere.

[1]: http://linuxfromscratch.org/blfs/view/svn/postlfs/firmware.html

Thanks.

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Re: What is the minimal set of firmware files I need for my hardware?

[Greg KH]

On Mon, May 04, 2020 at 01:26:35PM +0300, Doron Behar wrote:
> I hope this question fits to this List.
> 
> Today I learned that my distro's `linux-unfree-firmware` package is 491
> Mb in size. I'm pretty sure my hardware doesn't need all of these files.
> Maybe different Linux distros call this package differently, but I'm talking
> about the firmware files that come from:
> https://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git/
> 
> I think I can reduce this disk usage if I'll only know what files
> I can exclude from there.
> 
> Is there any official documentation, that states exactly what files from
> That git repo are needed per device / computer model? Perhaps the official
> documentation of my Computer's hardware will state that? There's a Linux
> from scratch webpage[1] that gives some info for popular hardware, but I'm
> wondering if there's a bit more "official" information available
> somewhere.
> 
> [1]: http://linuxfromscratch.org/blfs/view/svn/postlfs/firmware.html

The kernel macro MODULE_FIRMWARE() will show the firmware file that a
specific kernel module needs.  So if you look a the output of modinfo
for all of the modules that your system needs, you will see a "firmware"
line that shows the name that your hardware needs for that specific
driver/module.

Just take those specific files and put them on your disk and you should
be fine.  Note, I think tools that generate initrd images can do this
automatically, so perhaps you should look at what they do as an example
for this.

Hope this helps,

greg k-h

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Re: What is the minimal set of firmware files I need for my hardware?

[Doron Behar]

On Mon, May 04, 2020 at 12:45:55PM +0200, Greg KH wrote:
> On Mon, May 04, 2020 at 01:26:35PM +0300, Doron Behar wrote:
> > I hope this question fits to this List.
> > 
> > Today I learned that my distro's `linux-unfree-firmware` package is 491
> > Mb in size. I'm pretty sure my hardware doesn't need all of these files.
> > Maybe different Linux distros call this package differently, but I'm talking
> > about the firmware files that come from:
> > https://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git/
> > 
> > I think I can reduce this disk usage if I'll only know what files
> > I can exclude from there.
> > 
> > Is there any official documentation, that states exactly what files from
> > That git repo are needed per device / computer model? Perhaps the official
> > documentation of my Computer's hardware will state that? There's a Linux
> > from scratch webpage[1] that gives some info for popular hardware, but I'm
> > wondering if there's a bit more "official" information available
> > somewhere.
> > 
> > [1]: http://linuxfromscratch.org/blfs/view/svn/postlfs/firmware.html
> 
> The kernel macro MODULE_FIRMWARE() will show the firmware file that a
> specific kernel module needs.  So if you look a the output of modinfo
> for all of the modules that your system needs, you will see a "firmware"
> line that shows the name that your hardware needs for that specific
> driver/module.

Thanks for replying greg,

So I have the command `modinfo` available, should I just iterate _all_
the files in /usr/lib/modules/5.6.7/kernel ? For example:

```
$ modinfo /usr/lib/modules/5.6.7/kernel/net/ieee802154/ieee802154.ko.xz
filename:       /usr/lib/modules/5.6.7/kernel/net/ieee802154/ieee802154.ko.xz
author:         Dmitry Eremin-Solenikov
description:    IEEE 802.15.4 configuration interface
license:        GPL v2
depends:        
retpoline:      Y
intree:         Y
name:           ieee802154
vermagic:       5.6.7 SMP mod_unload 
sig_id:         PKCS#7
signer:         
sig_key:        
sig_hashalgo:   unknown
signature:      
```

Doesn't seem informative regarding firmware files. Should I expect other
.ko.xz files to give a line with `firmware: `?

Plus, how do I know what modules does my system need and which it
doesn't?

Doron.

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Re: What is the minimal set of firmware files I need for my hardware?

[Greg KH]

On Mon, May 04, 2020 at 03:56:40PM +0300, Doron Behar wrote:
> On Mon, May 04, 2020 at 12:45:55PM +0200, Greg KH wrote:
> > On Mon, May 04, 2020 at 01:26:35PM +0300, Doron Behar wrote:
> > > I hope this question fits to this List.
> > > 
> > > Today I learned that my distro's `linux-unfree-firmware` package is 491
> > > Mb in size. I'm pretty sure my hardware doesn't need all of these files.
> > > Maybe different Linux distros call this package differently, but I'm talking
> > > about the firmware files that come from:
> > > https://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git/
> > > 
> > > I think I can reduce this disk usage if I'll only know what files
> > > I can exclude from there.
> > > 
> > > Is there any official documentation, that states exactly what files from
> > > That git repo are needed per device / computer model? Perhaps the official
> > > documentation of my Computer's hardware will state that? There's a Linux
> > > from scratch webpage[1] that gives some info for popular hardware, but I'm
> > > wondering if there's a bit more "official" information available
> > > somewhere.
> > > 
> > > [1]: http://linuxfromscratch.org/blfs/view/svn/postlfs/firmware.html
> > 
> > The kernel macro MODULE_FIRMWARE() will show the firmware file that a
> > specific kernel module needs.  So if you look a the output of modinfo
> > for all of the modules that your system needs, you will see a "firmware"
> > line that shows the name that your hardware needs for that specific
> > driver/module.
> 
> Thanks for replying greg,
> 
> So I have the command `modinfo` available, should I just iterate _all_
> the files in /usr/lib/modules/5.6.7/kernel ? For example:

No, don't iterate all kernel modules, unless you only built the modules
that you know you need for your hardware (like you can get by running
'make localmodconfig').

> 
> ```
> $ modinfo /usr/lib/modules/5.6.7/kernel/net/ieee802154/ieee802154.ko.xz
> filename:       /usr/lib/modules/5.6.7/kernel/net/ieee802154/ieee802154.ko.xz
> author:         Dmitry Eremin-Solenikov
> description:    IEEE 802.15.4 configuration interface
> license:        GPL v2
> depends:        
> retpoline:      Y
> intree:         Y
> name:           ieee802154
> vermagic:       5.6.7 SMP mod_unload 
> sig_id:         PKCS#7
> signer:         
> sig_key:        
> sig_hashalgo:   unknown
> signature:      
> ```
> 
> Doesn't seem informative regarding firmware files. Should I expect other
> .ko.xz files to give a line with `firmware: `?

Yes, try looking at btrtl.ko for an example.

The module you picked above does not need any firmware to control the
hardware it manages (hint, it's not a driver for any specific hardware,
just a protocol that other drivers use.)

> Plus, how do I know what modules does my system need and which it
> doesn't?

That's up to you to figure out if you are building your own kernel
image.

As I mentioned above, the 'make localmodconfig' is a nice quick shortcut
to get that done, I recommend using it by doing:
	- boot a distro kernel
	- plug in all devices you want to support
	- run 'make localmodconfig' to create a .config file based only
	  on the modules you have loaded in the system at that point in
	  time.
	- build the kernel with that .config file

hope this helps,

greg k-h

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Re: What is the minimal set of firmware files I need for my hardware?

[Doron Behar]

On Mon, May 04, 2020 at 03:06:10PM +0200, Greg KH wrote:
> On Mon, May 04, 2020 at 03:56:40PM +0300, Doron Behar wrote:
> > On Mon, May 04, 2020 at 12:45:55PM +0200, Greg KH wrote:
> > > On Mon, May 04, 2020 at 01:26:35PM +0300, Doron Behar wrote:
> > > > I hope this question fits to this List.
> > > > 
> > > > Today I learned that my distro's `linux-unfree-firmware` package is 491
> > > > Mb in size. I'm pretty sure my hardware doesn't need all of these files.
> > > > Maybe different Linux distros call this package differently, but I'm talking
> > > > about the firmware files that come from:
> > > > https://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git/
> > > > 
> > > > I think I can reduce this disk usage if I'll only know what files
> > > > I can exclude from there.
> > > > 
> > > > Is there any official documentation, that states exactly what files from
> > > > That git repo are needed per device / computer model? Perhaps the official
> > > > documentation of my Computer's hardware will state that? There's a Linux
> > > > from scratch webpage[1] that gives some info for popular hardware, but I'm
> > > > wondering if there's a bit more "official" information available
> > > > somewhere.
> > > > 
> > > > [1]: http://linuxfromscratch.org/blfs/view/svn/postlfs/firmware.html
> > > 
> > > The kernel macro MODULE_FIRMWARE() will show the firmware file that a
> > > specific kernel module needs.  So if you look a the output of modinfo
> > > for all of the modules that your system needs, you will see a "firmware"
> > > line that shows the name that your hardware needs for that specific
> > > driver/module.
> > 
> > Thanks for replying greg,
> > 
> > So I have the command `modinfo` available, should I just iterate _all_
> > the files in /usr/lib/modules/5.6.7/kernel ? For example:
> 
> No, don't iterate all kernel modules, unless you only built the modules
> that you know you need for your hardware (like you can get by running
> 'make localmodconfig').
> 
> > 
> > ```
> > $ modinfo /usr/lib/modules/5.6.7/kernel/net/ieee802154/ieee802154.ko.xz
> > filename:       /usr/lib/modules/5.6.7/kernel/net/ieee802154/ieee802154.ko.xz
> > author:         Dmitry Eremin-Solenikov
> > description:    IEEE 802.15.4 configuration interface
> > license:        GPL v2
> > depends:        
> > retpoline:      Y
> > intree:         Y
> > name:           ieee802154
> > vermagic:       5.6.7 SMP mod_unload 
> > sig_id:         PKCS#7
> > signer:         
> > sig_key:        
> > sig_hashalgo:   unknown
> > signature:      
> > ```
> > 
> > Doesn't seem informative regarding firmware files. Should I expect other
> > .ko.xz files to give a line with `firmware: `?
> 
> Yes, try looking at btrtl.ko for an example.
> 
> The module you picked above does not need any firmware to control the
> hardware it manages (hint, it's not a driver for any specific hardware,
> just a protocol that other drivers use.)

Cool! I see it now.

> > Plus, how do I know what modules does my system need and which it
> > doesn't?
> 
> That's up to you to figure out if you are building your own kernel
> image.
> 
> As I mentioned above, the 'make localmodconfig' is a nice quick shortcut
> to get that done, I recommend using it by doing:
> 	- boot a distro kernel
> 	- plug in all devices you want to support
> 	- run 'make localmodconfig' to create a .config file based only
> 	  on the modules you have loaded in the system at that point in
> 	  time.
> 	- build the kernel with that .config file

OK! I did all that, and ran make afterwards. Now, I got a few .ko files
found in the build directory, and it seems that these are definitely
just a selection of those found in my distro's kernel. I ran then:

    find -name '*.ko' -exec modinfo {} \; | grep '^firmware:'

So if I understand correctly. The files listed in the output of this
command are the only files I do need, assuming all of the modules where
loaded when I ran `make localmodconfig`.

I was connected to a WiFi network and I connected to a Bluetooth device
prior to running `make localmodconfig` - just to make sure I used all of
my hardware and that all of the kernel modules that might be relevant
were loaded.

I guess that now I just have to download these files only from
https://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git/

> 
> hope this helps,
> 
> greg k-h
> 

Thank you greg for you help and guidance :).

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