Messages in this thread | | | Date | Tue, 31 Oct 2023 07:58:00 +0100 | From | Greg Kroah-Hartman <> | Subject | Re: How to pass software configuration to driver built as module in boot up phase |
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On Tue, Oct 31, 2023 at 10:56:23AM +0800, Tingwei Zhang wrote: > On 10/30/2023 7:30 PM, Greg Kroah-Hartman wrote: > > On Mon, Oct 30, 2023 at 07:21:48PM +0800, Tingwei Zhang wrote: > > > Hi Masami, Greg and Rafael, > > > > > > I have one driver that needs a bunch to software configuration like 1000 > > > settings. These settings can be different according to the use case. > > > > That seems very odd, what type of driver is this? > The example use case is below DCC driver which is a DMA engine. It can be > configured to read/write registers while whose registers need to be > configured by software. It's mainly used to debug device crash issue. > https://lore.kernel.org/lkml/cover.1691496290.git.quic_schowdhu@quicinc.com/T/
Given that no one listened to my last review cycle of that driver, why are you asking us again?
> > > They are required in boot up phase so we can't reply on user space to make > > > the configuration. > > > > > > Boot config is not preferred since we'd like to build that driver as dynamic > > > load Kernel module. > > > > > > Could you let me know if there's any mechanism in Kernel to do that? > > > > What is wrong with the existing ways of doing this that all other > > drivers use? > I'm not aware of all the existing ways. Below ways are what I know and they > may not be suitable for some reason. > 1. Let user space to configure with sysfs/debugfs/ioctl interface. Since we > need this configuration to be done in early stage before user space is up.
I really doubt that you need this before userspace starts, as that's not what "device crash" stuff should be dealing with. That happens after init starts, because you have a working kernel (i.e. this is not for hardware bringup.)
> This doesn't work.
Why do you need this before init? Specific reasons please.
> 2. Use device tree to pass the configuration to driver. Since the > configuration is software configuration instead of hardware descirption. It > doesn't fit in device tree. > 3. Boot config or commandline parameter. If the driver is built in, it can > work. But it doesn't work for dynamically loadable Kernel module.
If you have a module, then you can do this after init starts, so you are reporting conflicting "requirements" here, which make this impossible for us to understand :(
Please work with the kernel developers at your company to come up with a solution for this, you have the experience, do not require the community to do your work for you.
thanks,
greg k-h
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