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Hi Vivek,
> I have kernel
modules for USB Host, device and OTG. > These platform drivers ( usb bus driver (h/w drivers)). > > As of now I am using EXPORT_SYMBOL to export a > variable flag for doing Inter-Module-communication. > Problem: other modules which are using this variable > fail while doing insmod if original module exporting > this variable is Not loaded. > > So I am looking a way in which I don’t have to worry > if my original module is loaded or not.
So you are asking this: Module A exports symbol "x" and module "B" uses it. Now you want to be able to load module B irrespective of whether module A is loaded or not. Right?
But in the case module A is not loaded, where do you expect the module B to resolve the references to "x" from? You cannot have undefined references, and there HAS to be a definition for the module to be loaded.
> For this I need to check for the export symbol via c > code (module code, or ko file code). > > Again I can check in System.map but I am on > embedded board, so I don’t have System.map > on my up and running linux image.
Firstly you cannot read / write files from a kernel module. Secondly, the undefined references have to be resolved BEFORE the control reaches your module initialization code (MODULE_INIT). Thirdly, even if you some how were to magically determine that the symbol is not defined in the kernel, what do you plan to do in order to provide a definition of "x"?
Thanks,
Rajat
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Message-----
Hi Vivek,
What you are trying to do is very unclear.
> 1. Is there a way of exporting symbol kernel?
Ofcourse, EXPORT_SYMBOL(). Wait, did I understand your question correctly?
> 2. Or is there any way which I can check if symbol is present in the kernel in c code?
Check it in kallsyms
> 3. Or Can I load the Module A from Module B [in c code] (without using modprobe).
Huh? Are you trying to load a module from C code in kernel space? N-O-!. Yes, a C code in application space can load modules.
Thanks,
Rajat |
