From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=56417 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1PmQwn-0006NN-Vl for qemu-devel@nongnu.org; Mon, 07 Feb 2011 08:21:10 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1PmQwj-0003Ee-8e for qemu-devel@nongnu.org; Mon, 07 Feb 2011 08:16:02 -0500 Received: from mail-ww0-f41.google.com ([74.125.82.41]:42232) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1PmQwj-0003EW-1X for qemu-devel@nongnu.org; Mon, 07 Feb 2011 08:16:01 -0500 Received: by wwi18 with SMTP id 18so2840525wwi.4 for ; Mon, 07 Feb 2011 05:16:00 -0800 (PST) Message-ID: <4D4FF08D.2040505@codemonkey.ws> Date: Mon, 07 Feb 2011 07:15:57 -0600 From: Anthony Liguori MIME-Version: 1.0 Subject: Re: [Qemu-devel] [PATCH 03/16] qdev-properties: add PROP_TYPE_ENUM References: <1296773152-23279-1-git-send-email-alevy@redhat.com> <1296773152-23279-4-git-send-email-alevy@redhat.com> <20110207104348.GA5754@playa.tlv.redhat.com> In-Reply-To: <20110207104348.GA5754@playa.tlv.redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Markus Armbruster , qemu-devel@nongnu.org On 02/07/2011 04:43 AM, Alon Levy wrote: > 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 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 >>> --- >>> 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? > > In summary I guess data is a terrible name, but it was least amount of change. Happy > to take suggestions. > > >>> + >>> + 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, "", option->value) > > >>> +} >>> + >>> +static int print_enum_options(DeviceInfo *info, Property *prop, char *dest, size_t len) >>> +{ >>> + int ret = 0; >>> + EnumTable *option = (EnumTable*)prop->data; >>> >> Please don't cast from void * to pointer type (this isn't C++). >> >> > fixing. > > >>> + while (option->name != NULL) { >>> + ret += snprintf(dest + ret, len - ret, "%s", option->name); >>> + if (option[1].name != NULL) { >>> + ret += snprintf(dest + ret, len - ret, "/"); >>> + } >>> + option++; >>> + } >>> + return ret; >>> +} >>> + >>> +PropertyInfo qdev_prop_enum = { >>> + .name = "enum", >>> + .type = PROP_TYPE_ENUM, >>> + .size = sizeof(uint32_t), >>> + .parse = parse_enum, >>> + .print = print_enum, >>> + .print_options = print_enum_options, >>> +}; >>> + >>> /* --- 8bit integer --- */ >>> >>> static int parse_uint8(DeviceState *dev, Property *prop, const char *str) >>> diff --git a/hw/qdev.h b/hw/qdev.h >>> index 3d9acd7..3701d83 100644 >>> --- a/hw/qdev.h >>> +++ b/hw/qdev.h >>> @@ -102,6 +102,7 @@ enum PropertyType { >>> PROP_TYPE_VLAN, >>> PROP_TYPE_PTR, >>> PROP_TYPE_BIT, >>> + PROP_TYPE_ENUM, >>> }; >>> >>> struct PropertyInfo { >>> @@ -121,6 +122,11 @@ typedef struct GlobalProperty { >>> QTAILQ_ENTRY(GlobalProperty) next; >>> } GlobalProperty; >>> >>> +typedef struct EnumTable { >>> + const char *name; >>> + uint32_t value; >>> +} EnumTable; >>> + >>> /*** Board API. This should go away once we have a machine config file. ***/ >>> >>> DeviceState *qdev_create(BusState *bus, const char *name); >>> @@ -235,6 +241,7 @@ extern PropertyInfo qdev_prop_drive; >>> extern PropertyInfo qdev_prop_netdev; >>> extern PropertyInfo qdev_prop_vlan; >>> extern PropertyInfo qdev_prop_pci_devfn; >>> +extern PropertyInfo qdev_prop_enum; >>> >>> #define DEFINE_PROP(_name, _state, _field, _prop, _type) { \ >>> .name = (_name), \ >>> @@ -257,6 +264,14 @@ extern PropertyInfo qdev_prop_pci_devfn; >>> + type_check(uint32_t,typeof_field(_state, _field)), \ >>> .defval = (bool[]) { (_defval) }, \ >>> } >>> +#define DEFINE_PROP_ENUM(_name, _state, _field, _defval, _options) { \ >>> + .name = (_name), \ >>> + .info =&(qdev_prop_enum), \ >>> + .offset = offsetof(_state, _field) \ >>> + + type_check(uint32_t,typeof_field(_state, _field)), \ >>> + .defval = (uint32_t[]) { (_defval) }, \ >>> + .data = (void*)(_options), \ >>> >> Please don't cast from pointer type to void * (this isn't C++). If >> someone accidentally passes an integral argument for _options (forgotten >> operator&), the cast suppresses the warning. >> >> > fixing. > > >>> + } >>> >>> #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. > This is wrong. Libvirt should query this information through QMP. This is my main concern with enums. If there isn't a useful introspection interface, libvirt is going to do dumb things like query help output. This has been a nightmare historically and I'm not inclined to repeat it. Regards, Anthony Liguori