[cocci] Search for the concatenation of meta variable + fixed string (similar fresh identifier)

Hello again :)

In Linux, the DEVICE_ATTR_RO macro works like this:

static ssize_t led_status_show(struct device *dev, struct 
device_attribute *attr, char *buf) { /* ... */ }

// The macro automatically concatenates led_status + _show for struct 
initialization.
static DEVICE_ATTR_RO(led_status);


I'd like to find the position of all functions assigned by 
DEVICE_ATTR_RO. So I thought to use a 1st rule to search for the 
identifier inside DEVICE_ATTR_RO, then use a 2nd rule to search for the 
inherited meta variable, concatenated with the fixed string "_show". 
Like:

@device_attr_ro@
declarer name DEVICE_ATTR_RO;
identifier attr_name;
@@
   DEVICE_ATTR_RO(attr_name);

@device_attr_ro_show_fn@
identifier device_attr_ro.attr_name;
position p_fn;
@@
   attr_name ## "_show" @ p_fn (...) {...}     // invalid syntax, but you 
get the point


This doesn't work and I couldn't figure how to do it correctly. There's 
"fresh identifier" which looks close, but it only works for +, not for 
search context. Is such a search possible? How?

Tobias