But maybe in lieu of my comments you can ack this patch and I'll submit another one commenting this code and the pre-existing code that does the same stuff? Would make things a bit easier.. ;-)

/Nils
On Nov 9, 2010, at 6:45 PM, Nils Carlson wrote:

Some commentary on the comments below... :-)

On Nov 9, 2010, at 5:28 PM, David Goulet wrote:

Comments below.

On 10-11-04 12:54 PM, Nils Carlson wrote:

Signed-off-by: Nils Carlson<[email protected]>
---
libustcomm/ustcomm.c |   32 ++++++++++++++++++++++++++++++++
libustcomm/ustcomm.h |   11 +++++++++++
2 files changed, 43 insertions(+), 0 deletions(-)

diff --git a/libustcomm/ustcomm.c b/libustcomm/ustcomm.c
index fe8fea2..7d0fe00 100644
--- a/libustcomm/ustcomm.c
+++ b/libustcomm/ustcomm.c
@@ -621,6 +621,38 @@ char * ustcomm_restore_ptr(char *ptr, char *data_field, int data_field_size)
        return data_field + (long)ptr;
}

+int ustcomm_pack_trace_info(struct ustcomm_header *header,
+                           struct ustcomm_trace_info *trace_inf,
+                           const char *trace)
+{
+       int offset = 0;
+
+       trace_inf->trace = ustcomm_print_data(trace_inf->data,
+                                             sizeof(trace_inf->data),
+                                       &offset,
+                                             trace);

In order to understand this "data flow", I put some printf here to output me the "trace_inf->trace" (that in my understanding, should be the trace name with some other stuff...?) but each time it's NULL

It appears that you are passing "trace" to ustcomm_print_data and it using it as a "format" and results in having :

trace_inf->trace = NULL
trace_inf->data = "auto"

I'm wondering if this is correct ? (Maybe a little comment on print_data function to tell what kind of output it's generating?)

Can add a comment. What it does is that it packs the data and assigns relative pointers, so the NULL there is the relative position of trace_inf->trace within the data field. The unpack function restores these pointers by adding the address of the data field to each of them.


+
+       if (trace_inf->trace == USTCOMM_POISON_PTR) {
+               return -ENOMEM;
+       }
+
+       header->size = COMPUTE_MSG_SIZE(trace_inf, offset);
+
+       return 0;
+}
+
+
+int ustcomm_unpack_trace_info(struct ustcomm_trace_info *trace_inf)
+{
+       trace_inf->trace = ustcomm_restore_ptr(trace_inf->trace,
+                                              trace_inf->data,
+                                              sizeof(trace_inf->data));
+       if (!trace_inf->trace) {
+               return -EINVAL;
+       }
+
+       return 0;
+}

int ustcomm_pack_channel_info(struct ustcomm_header *header,
                              struct ustcomm_channel_info *ch_inf,
diff --git a/libustcomm/ustcomm.h b/libustcomm/ustcomm.h
index f62250c..d548bc1 100644
--- a/libustcomm/ustcomm.h
+++ b/libustcomm/ustcomm.h
@@ -78,6 +78,11 @@ enum tracectl_commands {
        STOP_TRACE,
};

+struct ustcomm_trace_info {
+       char *trace;

Would not be better to call the above variable something like "trace_name" because it's becoming quite confusing in the code with "trace" all over the place.

If so, maybe change the name all over the code from const char *trace to const char *trace_name


Well, we use the term *marker and *channel to denote their names, so it makes sense to do the same with *trace inside ustcomm.
The good news is then that ustcomm is internally consistent.

Will add a comment explaining how our home-made RPC works.

/Nils

Some other comment in the next patch but it follow these a bit.

Thanks
David

+       char data[USTCOMM_DATA_SIZE];
+};
+
struct ustcomm_channel_info {
        char *channel;
        unsigned int subbuf_size;
@@ -172,6 +177,12 @@ extern char * ustcomm_restore_ptr(char *ptr, char *data_field,
        (size_t) (long)(struct_ptr)->data - (long)(struct_ptr) + (offset)

/* Packing and unpacking functions, making life easier */
+extern int ustcomm_pack_trace_info(struct ustcomm_header *header,
+                                  struct ustcomm_trace_info *trace_inf,
+                                  const char *trace);
+
+extern int ustcomm_unpack_trace_info(struct ustcomm_trace_info *trace_inf);
+
extern int ustcomm_pack_channel_info(struct ustcomm_header *header,
                                     struct ustcomm_channel_info *ch_inf,
                                     const char *channel);

--
David Goulet
LTTng project, DORSAL Lab.

PGP/GPG : 1024D/16BD8563
BE3C 672B 9331 9796 291A  14C6 4AF7 C14B 16BD 8563

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