Re: [Qemu-devel] [PATCH 1/2] qemu-help: Sort devices by logical functionality

["Michael S. Tsirkin" <mst@redhat.com>]

On Sun, Jul 28, 2013 at 12:14:53PM +0300, Marcel Apfelbaum wrote:
> Categorize devices that appear as output to "-device ?" command
> by logical functionality. Sort the devices by logical categories
> before showing them to user.
> 
> The sort is done by functionality rather than alphabetical.
> 
> Signed-off-by: Marcel Apfelbaum <marcel.a@redhat.com>
> ---
> Changes from RFC
> Made category a bitmap to support multifunction PCI devices
> 
>  include/hw/qdev-core.h | 15 ++++++++++++
>  qdev-monitor.c         | 62 ++++++++++++++++++++++++++++++++++++++++++++++++--
>  2 files changed, 75 insertions(+), 2 deletions(-)
> 
> diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h
> index 7fbffcb..9130f97 100644
> --- a/include/hw/qdev-core.h
> +++ b/include/hw/qdev-core.h
> @@ -17,6 +17,19 @@ enum {
>  #define DEVICE_CLASS(klass) OBJECT_CLASS_CHECK(DeviceClass, (klass), TYPE_DEVICE)
>  #define DEVICE_GET_CLASS(obj) OBJECT_GET_CLASS(DeviceClass, (obj), TYPE_DEVICE)
>  
> +#define MAX_DEVICE_CATEGORY 8

make this the last entry in the enum, also rename
DEVICE_CATEGORY_MAX.
This way you won't have to change it manually each time you add
a category.

> +
> +typedef enum DeviceCategory {
> +    DEVICE_CATEGORY_ASSEMBLY,
> +    DEVICE_CATEGORY_MANAGEMENT,
> +    DEVICE_CATEGORY_STORAGE,
> +    DEVICE_CATEGORY_NETWORK,
> +    DEVICE_CATEGORY_INPUT,
> +    DEVICE_CATEGORY_DISPLAY,
> +    DEVICE_CATEGORY_SOUND,
> +    DEVICE_CATEGORY_MISC,
> +} DeviceCategory;
> +


I think it's nasty that all users need to shift.

One option is to name the enum fields with _SHIFT or _BIT
suffix, and define macros
#define DEVICE_CATEGORY_ASSEMBLY (1 << DEVICE_CATEGORY_ASSEMBLY_SHIFT)
Then we don't need to have this shift everywhere these
are used.

Another is to use set_bit to set bits.
I think I prefer this last variant.


>  typedef int (*qdev_initfn)(DeviceState *dev);
>  typedef int (*qdev_event)(DeviceState *dev);
>  typedef void (*qdev_resetfn)(DeviceState *dev);
> @@ -80,6 +93,8 @@ typedef struct DeviceClass {
>      ObjectClass parent_class;
>      /*< public >*/
>  
> +    /* DeviceCategory bitmap */
> +    unsigned int categories;

So why not use DECLARE_BITMAP?
You will also be able to use test_bit instead of
shifting everywhere.

>      const char *fw_name;
>      const char *desc;
>      Property *props;
> diff --git a/qdev-monitor.c b/qdev-monitor.c
> index e54dbc2..2e6d14e 100644
> --- a/qdev-monitor.c
> +++ b/qdev-monitor.c
> @@ -51,6 +51,18 @@ static const QDevAlias qdev_alias_table[] = {
>      { }
>  };
>  
> +/* Category names corresponding to DeviceCategory values */
> +static const char *qdev_category_names[] = {
> +    "Assembly",
> +    "Management",
> +    "Storage",
> +    "Network",
> +    "Input",
> +    "Display",
> +    "Sound",
> +    "Misc",
> +};

Offsets here correspond to specific enums.
Maybe make this explicit?

> +static const char *qdev_category_names[] = {
> +    .[DEVICE_CATEGORY_ASSEMBLY] = "Assembly",

etc.

Also, when adding a new category we'll need to add
a new entry here.
Maybe put both arrays together in the header so it's
harder to miss, and add a comment about it?


> +
>  static const char *qdev_class_get_alias(DeviceClass *dc)
>  {
>      const char *typename = object_class_get_name(OBJECT_CLASS(dc));
> @@ -75,11 +87,20 @@ static bool qdev_class_has_alias(DeviceClass *dc)
>      return (qdev_class_get_alias(dc) != NULL);
>  }
>  
> +typedef struct PrintDevInfoData {
> +    bool *show_no_user;
> +    DeviceCategory *category;
> +} PrintDevInfoData ;
> +

Why pointer to bool/category? Cleaner to pass it by instance I think.

>  static void qdev_print_devinfo(ObjectClass *klass, void *opaque)
>  {
>      DeviceClass *dc;
> -    bool *show_no_user = opaque;
> +    PrintDevInfoData *data = opaque;
> +    bool *show_no_user;
> +    DeviceCategory category;
>  
> +    show_no_user = data ? data->show_no_user : NULL;
> +    category = data && data->category ? *data->category : 0;
>      dc = (DeviceClass *)object_class_dynamic_cast(klass, TYPE_DEVICE);
>  
>      if (!dc || (show_no_user && !*show_no_user && dc->no_user)) {
> @@ -93,6 +114,18 @@ static void qdev_print_devinfo(ObjectClass *klass, void *opaque)
>      if (qdev_class_has_alias(dc)) {
>          error_printf(", alias \"%s\"", qdev_class_get_alias(dc));
>      }
> +    if (dc->categories) {
> +        if (dc->categories & (1 << category)) {
> +            error_printf(", category \"%s\"", qdev_category_names[category]);
> +        } else {
> +            error_printf(", categories");
> +            for (category = 0; category < MAX_DEVICE_CATEGORY; ++category) {
> +                if (dc->categories & (1 << category)) {
> +                    error_printf(" \"%s\"", qdev_category_names[category]);
> +                }
> +            }
> +        }
> +    }
>      if (dc->desc) {
>          error_printf(", desc \"%s\"", dc->desc);
>      }
> @@ -139,6 +172,23 @@ static const char *find_typename_by_alias(const char *alias)
>      return NULL;
>  }
>  
> +static GSList *qdev_get_devices_by_category(unsigned long categories)

In practice this gets a single category right?
So just pass the bit number, makes it more consistent.

> +{
> +    DeviceClass *dc;
> +    GSList *list, *curr, *ret_list = NULL;
> +
> +    list = object_class_get_list(TYPE_DEVICE, false);
> +    for (curr = list; curr; curr = g_slist_next(curr)) {
> +        dc = (DeviceClass *)object_class_dynamic_cast(curr->data, TYPE_DEVICE);
> +        if ((dc->categories & categories) == categories) {

I don't see where you would want to print only
devices that match a mask exactly.

With a single category,
        if (dc->categories & categories)
is equivalent and easier to understand.


> +            ret_list = g_slist_append(ret_list, dc);
> +        }
> +    }
> +    g_slist_free(list);
> +
> +    return ret_list;
> +}
> +
>  int qdev_device_help(QemuOpts *opts)
>  {
>      const char *driver;
> @@ -148,7 +198,15 @@ int qdev_device_help(QemuOpts *opts)
>      driver = qemu_opt_get(opts, "driver");
>      if (driver && is_help_option(driver)) {
>          bool show_no_user = false;
> -        object_class_foreach(qdev_print_devinfo, TYPE_DEVICE, false, &show_no_user);
> +        DeviceCategory category;
> +        PrintDevInfoData data = { &show_no_user, &category };
> +

So just drop show_no_user and category local vars, and use
data.show_no_user data.category.

> +        for (category = 0; category < MAX_DEVICE_CATEGORY; ++category) {
> +            GSList *list = qdev_get_devices_by_category(1 << category);
> +            g_slist_foreach(list, (GFunc)qdev_print_devinfo, &data);
> +            g_slist_free(list);
> +        }
> +
>          return 1;
>      }
>  
> -- 
> 1.8.3.1
>