Re: [Qemu-devel] [PATCH V1 02/10] qemu-clk: allow to attach a clock to a device

[Peter Maydell]

On 5 October 2016 at 23:10,  <address@hidden> wrote:
> From: KONRAD Frederic <address@hidden>
>
> This allows to attach a clock to a DeviceState.
> Contrary to gpios, the clock pins are not contained in the DeviceState but
> with the child property so they can appears in the qom-tree.

Is this API patterned along the same lines as some other
API we already have ? If so, it would be helpful to mention
it in the commit message.

(Also this series would probably benefit from somebody who
actually knows how the QOM APIs are supposed to work having
a look at it.)

> Signed-off-by: KONRAD Frederic <address@hidden>
> ---
>  include/qemu/qemu-clock.h | 24 +++++++++++++++++++++++-
>  qemu-clock.c              | 23 +++++++++++++++++++++++
>  2 files changed, 46 insertions(+), 1 deletion(-)
>
> diff --git a/include/qemu/qemu-clock.h b/include/qemu/qemu-clock.h
> index e7acd68..1d56a2e 100644
> --- a/include/qemu/qemu-clock.h
> +++ b/include/qemu/qemu-clock.h
> @@ -33,8 +33,30 @@
>  typedef struct qemu_clk {
>      /*< private >*/
>      Object parent_obj;
> +    char *name;            /* name of this clock in the device. */
>  } *qemu_clk;
>
> -#endif /* QEMU_CLOCK_H */
> +/**
> + * qemu_clk_attach_to_device:
> + * @dev: the device on which the clock need to be attached.
> + * @clk: the clock which need to be attached.
> + * @name: the name of the clock can't be NULL.
> + *
> + * Attach @clk named @name to the device @dev.

I'm not quite sure what this function does, but it looks like
what it actually does is attach @clk to device @dev as a
clock named @name.

> + *
> + */
> +void qemu_clk_attach_to_device(DeviceState *dev, qemu_clk clk,
> +                               const char *name);
>
> +/**
> + * qemu_clk_get_pin:
> + * @dev: the device which contain the clock.
> + * @name: the name of the clock.
> + *
> + * Get the clock named @name located in the device @dev, or NULL if not 
> found.
> + *
> + * Returns the clock named @name contained in @dev.
> + */
> +qemu_clk qemu_clk_get_pin(DeviceState *dev, const char *name);

I don't understand the name of this function. It says "get_pin"
but it returns a clock, not a pin ?

> +#endif /* QEMU_CLOCK_H */
> diff --git a/qemu-clock.c b/qemu-clock.c
> index ceea98d..0ba6caf 100644
> --- a/qemu-clock.c
> +++ b/qemu-clock.c
> @@ -25,6 +25,7 @@
>  #include "qemu/qemu-clock.h"
>  #include "hw/hw.h"
>  #include "qemu/log.h"
> +#include "qapi/error.h"
>
>  #ifndef DEBUG_QEMU_CLOCK
>  #define DEBUG_QEMU_CLOCK 0
> @@ -36,6 +37,28 @@
>      }                                                                        
> \
>  } while (0);
>
> +void qemu_clk_attach_to_device(DeviceState *dev, qemu_clk clk,
> +                               const char *name)
> +{
> +    assert(name);
> +    assert(!clk->name);

This is really checking that the clock hasn't already been attached
to something else, right?

> +    object_property_add_child(OBJECT(dev), name, OBJECT(clk), &error_abort);
> +    clk->name = g_strdup(name);

When does this string get freed?

> +}
> +
> +qemu_clk qemu_clk_get_pin(DeviceState *dev, const char *name)
> +{
> +    gchar *path = NULL;
> +    Object *clk;
> +    bool ambiguous;
> +
> +    path = g_strdup_printf("%s/%s", object_get_canonical_path(OBJECT(dev)),
> +                           name);
> +    clk = object_resolve_path(path, &ambiguous);

Needs a QOM API expert, but I'm about 90% certain that you
don't need to go via the canonical path to get hold of
an object that's a child of some other object you already
have. (Also object_resolve_path() accepts NULL if you
don't care about the return value in 'ambiguous', but I
think you'll end up not needing to call it at all.)
Possibly you want object_resolve_path_component(OBJECT(dev), name) ?

> +    g_free(path);
> +    return QEMU_CLOCK(clk);
> +}
> +
>  static const TypeInfo qemu_clk_info = {
>      .name          = TYPE_CLOCK,
>      .parent        = TYPE_OBJECT,
> --
> 2.5.5
>

thanks
-- PMM