Messages in this thread | | | Date | Thu, 11 Feb 2021 10:06:46 +0000 | From | Jonathan Cameron <> | Subject | Re: [PATCH v2 4/8] cxl/mem: Add basic IOCTL interface |
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On Wed, 10 Feb 2021 20:40:52 -0800 Dan Williams <dan.j.williams@intel.com> wrote:
> On Wed, Feb 10, 2021 at 10:47 AM Jonathan Cameron > <Jonathan.Cameron@huawei.com> wrote: > [..] > > > +#define CXL_CMDS \ > > > + ___C(INVALID, "Invalid Command"), \ > > > + ___C(IDENTIFY, "Identify Command"), \ > > > + ___C(MAX, "Last command") > > > + > > > +#define ___C(a, b) CXL_MEM_COMMAND_ID_##a > > > +enum { CXL_CMDS }; > > > + > > > +#undef ___C > > > +#define ___C(a, b) { b } > > > +static const struct { > > > + const char *name; > > > +} cxl_command_names[] = { CXL_CMDS }; > > > +#undef ___C > > > > Unless there are going to be a lot of these, I'd just write them out long hand > > as much more readable than the macro magic. > > This macro magic isn't new to Linux it was introduced with ftrace: > > See "cpp tricks and treats": https://lwn.net/Articles/383362/
Yeah. I've dealt with that one a few times. It's very cleaver and compact but a PITA to debug build errors related to it.
> > > > > enum { > > CXL_MEM_COMMAND_ID_INVALID, > > CXL_MEM_COMMAND_ID_IDENTIFY, > > CXL_MEM_COMMAND_ID_MAX > > }; > > > > static const struct { > > const char *name; > > } cxl_command_names[] = { > > [CXL_MEM_COMMAND_ID_INVALID] = { "Invalid Command" }, > > [CXL_MEM_COMMAND_ID_IDENTIFY] = { "Identify Comamnd" }, > > /* I hope you never need the Last command to exist in here as that sounds like a bug */ > > }; > > > > That's assuming I actually figured the macro fun out correctly. > > To my mind it's worth doing this stuff for 'lots' no so much for 3. > > The list will continue to expand, and it eliminates the "did you > remember to update cxl_command_names" review burden permanently.
How about a compromise. Add a comment giving how the first entry expands to avoid people (me at least :) having to think their way through it every time?
Jonathan
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