Hi Guenter, > > > I was waiting for feedback from Wim, who submitted a similar driver, > > > about his > > > thoughts. Key question is how to reserve access to the shared resource - > > > either > > > through an exported function in the mfd driver requesting a mutex, or > > > through > > > request_muxed_region(). I am going back and forth myself on which one is > > > better. > > > > > > Maybe it does not really matter, but using a function has the slight > > > advantage > > > that it auto-loads and locks the mfd module while one of its client > > > modules > > > is loaded. If we use request_muxed_region, that is not the case and the > > > client > > > module must use another means to request and lock the mfd module. > > > > > > Maybe you have an opinion ? > > > > This is indeed the main issue that has to be solved. Both options will work. > > I like the auto-load and lock, but I need to look at the > > request_muxed_region > > code again first before I can see what the possible drawbacks are :-). > > > One drawback of using request_muxed_region is that it needs a return value > from superio_enter. Also, it needs some code in the client driver init > function > to ensure that the mfd driver gets loaded, and possibly a call to > __module_get() > in the client driver probe function to keep the mfd driver loaded. > > winbond_superio_enter() would not need a return value and could use > devm_request_region. We could also consider allocating the hwmon memory space > in > the mfd driver and pass it as resource to the client drivers, which would > remove > a few more lines of code from those. > > Overall I am slightly in favor of using an exported function.
I looked at commit 8b6d043b7ee2d1b819dc833d677ea2aead71a0c0 (which implements request_muxed_region). You indeed need some extra code for loading the lowl-level mfd driver. So I am also in favour of the exported function. Kind regards, Wim. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
