On Tue, Aug 22, 2023 at 09:21:19AM +0200, Geert Uytterhoeven wrote: > On Mon, Aug 21, 2023 at 7:09 PM Andy Shevchenko > <andriy.shevchenko@xxxxxxxxxxxxxxx> wrote: > > On Mon, Aug 21, 2023 at 05:40:05PM +0200, Geert Uytterhoeven wrote: > > > On Mon, Aug 21, 2023 at 5:25 PM Andy Shevchenko > > > <andriy.shevchenko@xxxxxxxxxxxxxxx> wrote: > > > > On Mon, Aug 21, 2023 at 03:27:43PM +0200, Geert Uytterhoeven wrote: > > > > > On Mon, Aug 21, 2023 at 3:04 PM Andy Shevchenko > > > > > <andriy.shevchenko@xxxxxxxxxxxxxxx> wrote: > > > > > > On Sun, Aug 20, 2023 at 07:44:00PM +0100, Biju Das wrote: ... > > > > > > For all your work likes this as I noted in the reply to Guenter that > > > > > > the couple of the selling points here are: > > > > > > 1) avoidance of the pointer abuse in OF table > > > > > > (we need that to be a valid pointer); > > > > > > > > > > There is no pointer abuse: both const void * (in e.g. of_device_id) > > > > > and kernel_ulong_t (in e.g. i2c_device_id) can be used by drivers > > > > > to store a magic cookie, being either a pointer, or an integer value. > > > > > The same is true for the various unsigned long and void * "driver_data" > > > > > fields in subsystem-specific driver structures. > > > > > > > > (void *)5 is the abuse of the pointer. > > > > We carry something which is not a valid pointer from kernel perspective. > > > > > > But the data field is not required to be a valid pointer. > > > What kind and type of information it represents is specific to the driver. > > > > Where to find necessary information which is not always an integer constant. > > For example, for the driver data that has callbacks it can't be invalid pointer. > > If the driver uses it to store callbacks, of course it needs to be a > valid pointer. But that is internal to the driver. It is not that > we're passing random integer values to a function that expects a > pointer that can actually be dereferenced. > > > Since OF ID table structure is universal, it uses pointers. Maybe you need to > > update it to use plain integer instead? > > It is fairly common in the kernel to use void * to indicate a > driver-specific cookie, being either a real pointer or an integral > value, that is passed verbatim. See also e.g. the "dev" parameter > of request_irq(). Yes, that parameter is void * due to calling kfree(free_irq(...)). So, that's argument for my concerns. > > I think there is no more sense to continue this. We have to admit we have > > a good disagreement on this and I do not see any way I can agree with your > > arguments. Note, I'm fine if you "fix" OF ID structure to use kernel_ulong_t. > > of_device_id is also used in userspace (e.g. modutils), but I believe > that uses a copy of the structure definition, not the definition from > the kernel headers. Nope, it uses the very same mod_devicetable.h in both. > Still, changing the type would be a lot of work, > for IMHO no real gain. So, stale mate here, then? > > The only objection there is that it may not carry on the const qualifier, > > which I personally find being a huge downside of the whole driver_data. > > I believe you haven't objected that. > > Having const is nice, indeed. At least something we have agreed on :-) -- With Best Regards, Andy Shevchenko
