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

From: KONRAD Frederic
Subject: Re: [Qemu-devel] [PATCH V1 02/10] qemu-clk: allow to attach a clock to a device
Date: Tue, 18 Oct 2016 09:20:07 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.2.0

Le 17/10/2016 à 20:13, Peter Maydell a écrit :
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.)

I CC'ed Andreas maybe he can help.

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 ?

Yes actually you're right. Only we only use this function outside the
model. In the machine when you want to connects the clock model
together. That's why I called it like that. But I can change if you

+#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"

@@ -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?

Nowhere actually! I'll fix that.

+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,

-- PMM

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