Messages in this thread | | | From | Masahiro Yamada <> | Date | Thu, 28 Jul 2016 19:52:06 +0900 | Subject | Re: Why do we need reset_control_get_optional() ? |
| |
Hi Arnd,
2016-07-28 19:09 GMT+09:00 Arnd Bergmann <arnd@arndb.de>: > On Thursday, July 28, 2016 11:43:00 AM CEST Philipp Zabel wrote: >> > I want to deprecate _optional variants in the following steps: >> > >> > [1] Add "depends on RESET_CONTROLLER" to drivers >> > for which reset_control is mandatory. >> > >> > We can find those driver easily by grepping >> > the reference to non-optional reset_control_get(). >> >> Since we have the stubs, the RESET_CONTROLLER dependency is only at >> runtime, not at build time. >> >> I think Arnd wanted to move this in the opposite direction and remove >> the configurable RESET_CONTROLLER symbol. Maybe we should let all >> drivers that currently request non-optional resets have: >> depends on (ARCH_HAS_)RESET_CONTROLLER || COMPILE_TEST >> ? > > There are various ways to improve the current situation. > > I think it's important that a driver that has an optional > reset line behaves in exactly the same way whether the reset > subsystem is enabled or disabled when no reset line is > provided for a machine. > > When a driver requires a reset line, we can either have a > build-time failure when the reset subsystem is disabled > (enforcing the Kconfig dependency), or cause a runtime > failure if either there is no reset line or the subsystem > is disabled.
Yes. I am suggesting the "enforcing the Kconfig dependency".
"I will let you build this driver, but it would never work" is not the right thing to do, I think.
> In my experimental patch, I make the _optional functions > return NULL if no "resets" property is provided but return > an error if there are reset lines but the subsystem is > disabled, i.e. an optional reset must be used if it's in the > DT, but can be ignored otherwise.
I do not like this idea.
reset_control_get() (or variants) should not return NULL, it is ambiguous. It should return ERR_PTR(-ENOENT) if no "resets" property.
I only want two types for functions that return a pointer.
[1] return a valid pointer on success, or return NULL on failure (for example, kmalloc()) [2] return a valid pointer on success, or return error pointer on failure (many of _register() functions)
Mixing [1] and [2] will be a mess.
-- Best Regards Masahiro Yamada
| |