> On Mon, May 06, 2019 at 05:46:56PM +0200, Esben Haabendal wrote: >> Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx> writes: >> >> > On Wed, May 01, 2019 at 09:17:37AM +0200, Esben Haabendal wrote: >> >> >> Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx> writes: > >> As an example, the sm501.c driver, the only driver in drivers/mfd/ which >> uses serial8250 driver, does not use any code from mfd-core. >> Incidentally, it is 1 year older than mfd-core.c, and as never been >> refactored to use mfd-core functionality. > > So, sm501.c should not request resources for its children. This as simple as > that. Funny thing. Even though sm501.c does not use mfd-core at all, it does request resources for all its child devices, except for the uart children. sm501_register_usbhost(), sm501_register_display() and sm501_register_gpio() all creates/requests resources. But sm501_register_uart() does not. How many concrete examples are needed to convince you that what I am trying to do is how it is done everywhere else (than serial8250_core.c/serial8250_port.c, even in other 8250_*.c drivers) (obviously not 100% true, there are ofcourse other pieces of code not working well with resource management) ? > What you are trying to do here is a hack workaround on the current > behaviour in the Linux device model (resource management) as I told > you already. No. If it was, then all (most) mfd drivers added after 2008 are hacky workarounds, because the use mfd_add_devices(). There are currently 53 drivers in drivers/mfd/ that calls mfd_add_devices() with one or more cells with resources attached. Are they all hacky workarounds? I am not trying to do anything that they are not already doing. >> > Why not? Again, *slicing* resources is OK and that's what MFD for, >> > *requesting* >> > them in the parent is not. >> >> Why we cannot use request_mem_region() for those memory resources again? > > Because it's how it was designed. "One device per one resource". If you would > like to fix this, it should be done obviously not in 8250 driver or any other > driver, but driver core. > > Nevertheless there is one particular exception here, > i.e. IORESOURCE_MUXED. I am not trying to fix the problem of having multiple drivers owning the same resource. I am just trying to make serial8250 driver behave so it can use the resources that it is handed by mfd-core. This really is how it (mfd and also device resource management) is designed. I am not inventing anything, or making a workaround. Actually, you should take a look at the following specialized 8250 8250_aspeed_vuart.c 8250_bcm2835aux.c 8250_dw.c 8250_em.c 8250_ingenic.c 8250_lpc18xx.c 8250_mtk.c 8250_omap.c 8250_pxa.c 8250_uniphier.c They all use platform_get_resource(), and will work nicely with mfd. And of-course, none of them use request_mem_region(). So, if you want to insist that I create a clone of the current standard serial8250 driver (serial8250_isa_driver in 8520_core.c), even though I want absolutely nothing specialized, just need it to play nicely with platform_get_resource(), what should I call the driver? 8520_plat.c ? >> It fails because the resources are now already owned the mfd driver, on >> behalf of the child. > > Yes. Behaves in order how it's implementer. No issues here. If that was the case, then mfd-core would be implemented in order to not work with existing platform drivers. There definitely is an issue here. And it is in 8250_core.c and 8250_port.c. >> > Nope, *requesting* resources as you mentioned lock them to the certain user. >> >> I still think there is some confusion in relation to your use of the >> word "requesting". There is no explicit request/lock action in >> kernel/resource.c. > > You have to check IORESOURCE_BUSY. It seems that what you missed in your > picture. Point taken. I haven't put much focus on that. But I don't see how that is going to help making use of serial8250_isa_driver in combination with mfd_add_devices(). I am not creating/requesting the resources. That is done by mfd_add_device(), which I fail to see why I would need to change. > I didn't comment the rest until we will figure out the IO resource management > in general. I believe all my comments were related to this same resource management discussion. /Esben
