On Mon, Feb 07, 2011 at 04:27:21PM +0200, Alon Levy wrote: > On Mon, Feb 07, 2011 at 03:00:25PM +0100, Markus Armbruster wrote: > > Alon Levy <al...@redhat.com> writes: > > > > > On Mon, Feb 07, 2011 at 09:53:44AM +0100, Markus Armbruster wrote: > > >> I haven't been able to follow the evolution of this series, my apologies > > >> if I'm missing things already discussed. > > >> > > >> Alon Levy <al...@redhat.com> writes: > > >> > > >> > Example usage: > > >> > > > >> > EnumTable foo_enum_table[] = { > > >> > {"bar", 1}, > > >> > {"buz", 2}, > > >> > {NULL, 0}, > > >> > }; > > >> > > > >> > DEFINE_PROP_ENUM("foo", State, foo, 1, foo_enum_table) > > >> > > > >> > When using qemu -device foodev,? it will appear as: > > >> > foodev.foo=bar/buz > > >> > > > >> > Signed-off-by: Alon Levy <al...@redhat.com> > > >> > --- > > >> > hw/qdev-properties.c | 60 > > >> > ++++++++++++++++++++++++++++++++++++++++++++++++++ > > >> > hw/qdev.h | 15 ++++++++++++ > > >> > 2 files changed, 75 insertions(+), 0 deletions(-) > > >> > > > >> > diff --git a/hw/qdev-properties.c b/hw/qdev-properties.c > > >> > index a493087..3157721 100644 > > >> > --- a/hw/qdev-properties.c > > >> > +++ b/hw/qdev-properties.c > > >> > @@ -63,6 +63,66 @@ PropertyInfo qdev_prop_bit = { > > >> > .print = print_bit, > > >> > }; > > >> > > > >> > +/* --- Enumeration --- */ > > >> > +/* Example usage: > > >> > +EnumTable foo_enum_table[] = { > > >> > + {"bar", 1}, > > >> > + {"buz", 2}, > > >> > + {NULL, 0}, > > >> > +}; > > >> > +DEFINE_PROP_ENUM("foo", State, foo, 1, foo_enum_table), > > >> > + */ > > >> > +static int parse_enum(DeviceState *dev, Property *prop, const char > > >> > *str) > > >> > +{ > > >> > + uint8_t *ptr = qdev_get_prop_ptr(dev, prop); > > >> > > >> uint8_t is inconsistent with print_enum() and DEFINE_PROP_ENUM(), which > > >> both use uint32_t. > > > > > > Thanks, fixing. > > > > > >> > > >> > + EnumTable *option = (EnumTable*)prop->data; > > >> > > >> Please don't cast from void * to pointer type (this isn't C++). > > >> > > > > > > Will fix for all references. > > > > > >> Not thrilled about the "void *data", to be honest. Smells like > > >> premature generality to me. > > >> > > > > > > I did put it in there because I didn't think a "EnumTable *enum" variable > > > would have been acceptable (added baggage just used by a single property > > > type), > > > and I didn't find any other place to add it. I guess I should just do a: > > > > > > typedef struct EnumProperty { > > > Property base; > > > EnumTable *table; > > > } EnumProperty; > > > > > > But then because we define the properties in a Property[] array this > > > won't work. > > > Maybe turn that into a Property* array? > > > > Doubt the additional complexity just for keeping EnumTable out of > > Property is worth it. > > > > > In summary I guess data is a terrible name, but it was least amount of > > > change. Happy > > > to take suggestions. > > > > Further down, we discuss the idea of supporting an EnumTable with > > arbitrary integer type properties. Would you find an EnumTable member > > of Property more palatable then? > > > > I would. > > > >> > + > > >> > + while (option->name != NULL) { > > >> > + if (!strncmp(str, option->name, strlen(option->name))) { > > >> > > >> Why strncmp() and not straight strcmp()? > > >> > > > > > > I guess no reason except "strncmp is more secure" but irrelevant here > > > since > > > option->name is from the source, I'll fix. > > > > > >> > + *ptr = option->value; > > >> > + return 0; > > >> > + } > > >> > + option++; > > >> > + } > > >> > + return -EINVAL; > > >> > +} > > >> > + > > >> > +static int print_enum(DeviceState *dev, Property *prop, char *dest, > > >> > size_t len) > > >> > +{ > > >> > + uint32_t *p = qdev_get_prop_ptr(dev, prop); > > >> > + EnumTable *option = (EnumTable*)prop->data; > > >> > + while (option->name != NULL) { > > >> > + if (*p == option->value) { > > >> > + return snprintf(dest, len, "%s", option->name); > > >> > + } > > >> > + option++; > > >> > + } > > >> > + return 0; > > >> > > >> Bug: must dest[0] = 0 when returning 0. > > >> > > > > > > will just return snprintf(dest, len, "<enum %d>", option->value) > > > > Print something useful is a good idea. I guess I'd print an unadorned > > "%d". > > > > Agreed. > > > >> > +} > > >> > + > > [...] > > >> > + } > > >> > > > >> > #define DEFINE_PROP_UINT8(_n, _s, _f, _d) \ > > >> > DEFINE_PROP_DEFAULT(_n, _s, _f, _d, qdev_prop_uint8, uint8_t) > > >> > > >> Okay, let's examine how your enumeration properties work. > > >> > > >> An enumeration property describes a uint32_t field of the state object. > > >> Differences to ordinary properties defined with DEFINE_PROP_UINT32: > > >> > > >> * info is qdev_prop_enum instead of qdev_prop_uint32. Differences > > >> between the two: > > >> > > >> - parse, print: symbolic names vs. numbers > > >> > > >> - name, print_options: only for -device DRIVER,\? (and name's use > > >> there isn't particularly helpful) > > > > > > Why do you say that? this is being used by libvirt to get the names of the > > > supported backends for the ccid-card-emulated device. > > > > Too terse, let me try again :) > > > > - name, print_options: differences not important here, because these > > members are they are only for -device DRIVER,\? > > > > By the way, I don't find help output like > > > > e1000.mac=macaddr > > e1000.vlan=vlan > > e1000.netdev=netdev > > > > particularly helpful. Not your fault, outside the scope of this > > patch. > > > > Right, you get strange "X=X" output most of the time, but with print_options > for enum types you actually get this: > > $ x86_64-softmmu/qemu-system-x86_64 -device ccid-card-emulated,? > ccid-card-emulated.backend=nss-emulated/certificates > > That's actually parsable. Of course I agree with Anthony that having a json > (QMP) > interface with properly quoted strings (here I don't take care of backslashes > in the EnumTable names for instance) would be much better. > > > >> > > >> * data points to an EnumTable, which is a map string <-> number. Thus, > > >> the actual enumeration is attached to the property declaration, not > > >> the property type (in programming languages, we commonly attach it to > > >> the type, not the variable declaration). Since it's a table it can be > > >> used for multiple properties with minimal fuss. Works for me. > > >> > > >> What if we want to enumerate values of fields with types other than > > >> uint32_t? > > >> > > >> C enumeration types, in particular. Tricky, because width and > > >> signedness of enum types is implementation-defined, and different enum > > >> types may differ there. > > >> > > > > > > I specifically used uint32_t expecting it to work for many uses. It would > > > be better to allow an arbitrary type, or just not require specifying the > > > type but getting it from the enum itself (using typeof?). But then you > > > can't have a single EnumTable because it's type is now dependent on the > > > enumeration type (of course I could resort to macros, but I don't want to > > > go there). > > > > That's what I meant when I called it "tricky". > > > > Still, having an enum property that cannot be used with enumeration > > types is kind of sad, isn't it? > > > > >> Perhaps what we really need is a way to define arbitrary integer type > > >> properties with an EnumTable attached. > > >> > > > > > > This sounds more promising. So you would have an EnumTableU32 etc and > > > DEFINE_PROP_{UINT8,..}_ENUM which takes an extra EnumTable of the correct > > > type, to be defined inline maybe so user doesn't actually declare it (like > > > no one declares Property thanks to the DEFINE_PROP_ macros). > > > > Sounds like what I have in mind. Care to explore it? > > > > One EnumTable should do, just make its member value wide enough. > > > > Ok, I can try that. Sounds like it should work. >
Changed my mind - Since libvirt is happy with a string, and this is not something I really have time to pursue, and Anthony is making a better solution IIUC, I'm dropping this. > > Note to maintainer: we don't have to get enum properties 100% right and > > polished before we can commit this series. > > >